1. The basic concepts of information technology

 

What is the difference between informatics and computer studies?

It is hard to draft the real difference between the two concepts. In Hungary, informatics means the theoretical side of information technology (software part), while computer studies mean the material side (hardware part). Basically in foreign countries, especially in England and in English language, computer studies are one thing and it is not separated into two pieces.

The definition of informatics: Informatics is the science of the computer systems, which gives the theoretical side to programming, designing and functioning. Informatics also includes the questions (and answers) of processing, storage and the transmission of data.

Computer science: An academic discipline that studies, among other topics, the mathematics of computation, the properties of algorithms and the design of programming languages. It should be distinguished from Computer Studies, which is a vocational course in the practical use of computers, and may include some computer science. Computer science is a relatively new science, founded in the years after WWII in the UK and USA. Its founding fathers include Alan Turing, whose paper on computable numbers could be said to be the founding document, and John von Neumann. However the earliest days there was no clear demarcation between computer science and computer engineering, and so hundreds of practical electronic engineers and compiler writers deserve an equal place in this Pantheon. Among the most important discoveries of computer science are those that concern the time and space complexity of algorithms, which allow the limits of computation to be understood, and the adaptation of Chomsky’s linguistic discoveries to describe the power of different classes of computing machine.

What is the role of computer studies in nowadays’ applied computer science?

 

What is information-technology? What are the basic roles of information –technology?

The definition of information-technology: The development, installation, and implementation of computer systems and applications. In other words: The blanket term that describes all the products and activities of the computing and telecommunications industries.

The basic concepts of information-technology:
- the hardware parts of computers

- the concept of operating system, and the function of a computer program

- the concepts of storage and memory

- the relationship between basic units of  stored data: - bit, byte, record, file

- the steps of expansion of a system – dissection, programming and adaptation

- the graphic based interface

- concepts related with multimedia

 

The simple model of transmission of information:

 

 

What are coding and decoding?

Forming the information is fundamental in computer science. To do this, the sender prepares the message with some kind of method (codeing), then the coded information is sent to the receiver through the communication channel, then the receiver converts the information back (decoding) to the original form. So this is the coding and decoding.

What is a code?

The word “code” has 3 meanings in computer studies:

1 – A system of letters or symbols together with rules for their combination, by means of which information can be represented or communicated for reasons of secrecy, brevity, identification or in order to be executed by a computer.

2 – Hence, the informal term used by programmers to refer to their product, namely executable computer programs whether in the original, human readable form called source code, or after compilation into object code. The term is also used as a verb meaning write programs.

3 – Sometimes encountered in mainframe computing circles in the plural form ‘codes’ referring to large computer application programs.

Decoding is the reverse of coding. Decoding converts the coded information back to the original form.

However coding is not just used in information transmission, it is also used to programming in programming languages.

The programming language: An invented language used to write computer programs, and designed to be  more readable by humans than binary machine code instructions are. The purpose of any programming language is to ease the task of writing error-free programs. There is no single universal programming language, but hundreds of different ones tailored to different kinds of computer application, and new ones are being developed all the time. The most widely used languages today are C, C++, BASIC, COBOL and FORTRAIN.

 

Examples for the procedure of information transmissions:

 

Internet; TV; telephone; radio-techniques; satellite etc.

 

2. History of computers

Earliest devices for facilitating human calculation

Humanity has used devices to aid in computation for millennia. One example is a device for establishing equality by weight: the classic scales later used to symbolize equality in justice. Another is simple enumeration: the checkered cloths of the counting houses served as simple data structures for enumerating stacks of coins, by weight. A more arithmetic-oriented machine is the abacus. One of the earliest machines of this type was the Roman abacus. Babylonians and others frustrated with counting on their fingers invented the Abacus.

First mechanical calculators

Gears are at the heart of mechanical devices like the Curta calculator.

In 1623 Wilhelm Schickard built the first mechanical calculator and thus became the father of the computing era. Since his machine used techniques such as cogs and gears first developed for clocks, it was also called a calculating clock. It was put to practical use by his friend Johannes Kepler, who revolutionized astronomy.

Machines by Blaise Pascal (the Pascaline, 1640) and Gottfried Wilhelm von Leibniz (1670) followed. Mechanical calculators, like the base-ten addiator, remained in use until the twentieth century.

Leibniz also described the binary numeral system, a central ingredient of all modern computers. However, up to the 1940s, many subsequent designs (including Charles Babbages machines of the 1800s and even ENIAC of 1945) were based on the harder-to-implement decimal system.

The slide rule, a basic mechanical calculator, facilitates multiplication and division.

John Napier noted that multiplication and division of numbers can be performed by addition and subtraction, respectively, of logarithms of those numbers. Since these real numbers can be represented as distances or intervals on a line, the slide rule allowed multiplication and division operations to be carried significantly faster than was previously possible. Slide rules were used by generations of engineers and other mathematically inclined professional workers, until the invention of the pocket calculator. The engineers in the Apollo program to send a man to the moon made many of their calculations on slide rules, which were accurate to 3 or 4 significant figures.

Punched card technology 1801–

In 1801, Joseph-Marie Jacquard developed a loom in which the pattern being woven was controlled by punched cards. The series of cards could be changed without changing the mechanical design of the loom. This was a landmark point in programmability. In the twentieth century, electricity was first used for calculating and sorting machines.

Herman Hollerith invented a tabulating machine using punch cards in the 1880s.

In 1890 the United States Census Bureau used punch cards and sorting machines designed by Herman Hollerith to handle the flood of data from the decennial census mandated by the Constitution. Holleriths company eventually became the core of IBM. IBM developed punch card technology into a powerful tool for business data processing and produced an extensive line of specialized unit record equipment. By 1950 the IBM card had become ubiquitous in industry and government. The warning printed on most cards, "Do not fold, staple or mutilate," became a motto for the post-World War II era.

First designs of programmable machines 1835–1900s

The defining feature of a "universal computer" is programmability, which allows the computer to emulate any other calculating machine by changing a stored sequence of instructions.

In 1835 Charles Babbage described his analytical engine. It was the plan of a general-purpose programmable computer, employing punch cards for input and a steam engine for power. One crucial invention was to use gears for the function served by the beads of an abacus. In a real sense, computers all contain automatic abaci (technically called the ALU or floating-point unit).

While the plans were probably correct, or at least debuggable, the project was slowed by disputes with the artisan who built parts. It was ended with the depletion of government funding.

Ada Lovelace, Lord Byrons daughter, translated and added notes to the "Sketch of the Analytical Engine" by Federico Luigi, Conte Menabrea. She has become closely associated with Babbage. Some claim she is the worlds first computer programmer, however this claim and the value of her other contributions are disputed by many.

A reconstruction of the Difference Engine II, an earlier, more limited design, has been operational since 1991 at the London Science Museum. With a few trivial changes, it works as Babbage designed it and shows that Babbage was right in theory.

Computer Generations

First generation (1945-54):

During the Second World War the British government’s pressing need to decode German intelligence produced using Enigma machine led to setting up of a team led by Turing, I. J. Good and D. Michie. This team produced Colossus, the firs valve-based computer, what was a special-purpose machine. Many historians think Britain would not have won the war without this.

At about the same time, work on general-purpose computer was also beginning at the Moore School of Engineering in Pennsylvania, USA, led by J. W. Mauchly and J. P. Eckert. This machine called ENIAC (Electronic Numerical Integrator and Calculator), was started in 1943 and finally completed in 1946. It contained 18-19000 valves (elektroncső) and consumed 150-175 kWh of power. In order to operate the machine reliably as possible, it had to remain switched on at all times, to reduce the chance of valve heaters burning out during switch-on power surge. Because of the short lifespan of the valves (2-3000 hours) the machine worked dependably for 3-5 days. ENIAC differed only in one significant way from computers of today: its program was stored externally. This meant the program had to be executed sequentially at the speed at which instructions could be read by the primitive card and paper tape readers used at the time. More at John von Neumann.

Basic ideas of Neumann (1946):

1. The computer should be serial-operated. The machine should execute the instructions one by one.
2. The computer should use binary system and should be totally electronic.
3. Stored program idea: the program to be executed is stored in exactly the same memory space as the data it is work upon. The distinguishes it from earlier computers whose functions were built immutably into the hardware, or whose programs existed in a different medium from their data (for example on punched cards).
4. The computer should have inner memory, and have to work manually by it. The processing unit should read and execute without human intervention.
5. The computer should be universal. We don’t need any special equipment for the execution of different works.

In 1949 started to work EDVAC (Electronic Discrete Variable Computer), which was initially program-orientated computer. The theorical basics of this computer were worked out by Neumann. The real new thing was the stored program control.

The first serial produced computer was the UNIVAC (Universal Automatic Computer) in 1951. During this time 6 computers worked worldwide.

Computer programming: First they programmed the computers by machine code.

Second generation (1955-65):

In 1958 transistor (invented in 1948) was used for the building computers, but another reliability problem emerged. As the complexity and processing power of computer increased, the limiting factor in reliability began to be the number of connections required between the components of computers.

Magnetic tapes and later magnetic discs take over the act of storage devices(háttértár).

Fortran (also FORTRAN) is a statically typed, compiled, programming language originally developed in the 1950s and still heavily used for scientific computing and numerical computation half a century later. The name is a portmanteau of Formula Translator/Translation. Early versions of the language were known as FORTRAN, but the capitalization has been dropped in newer revisions beginning with Fortran 90. The official language standards now refer to the language as "Fortran". With these new things the miniaturization started (computers are now below 1 km3).

Third generation (1966-81):

The first integrated circuits (invented in 1959) began to appear in the early 1960s. Integrated circuit, wherein the number of soldered connections was reduced by implementing larger and larger subsystems of the computer upon a single chip of silicon.

16 and later 64 bit memory.

In 1971 Intel developed small semiconductor firm called Intel that was a set of component which enabled a computer to be constructed on a single circuit board. This chip set (which had about the same computing power as the original ENIAC) was originally designed for a specific product (a Japanese calculator), but Intel was quick to realize its more potential, and marketed it as the MCS-4 microcomputer. Though the complete computer required a whole board of electronics, the central processing unit (CPU), or brain of the computer, was contained on a single chip for the first time, and this chip became known as microprocessor (Intel 4004 CPU).

The computer was controlled by a set of programs called the operating system.

In 1964 they started to develop BASIC (Beginners All-purpose Symbolic Instruction Code) under the leading of John G. Kemény. (The programming languages were improved (ALGOL, COBOL, and FORTRAN). In 1968 Niklaus Wirth made Pascal language which became well known. C programming language was born in the Bell Laboratory in 1974 by the work of Keringhan and Ritchie.

Fourth Generation (1980’s)

Computers built after 1972 are often called fourth generation computers, based on LSI (Large Scale Integration) of circuits (such as microprocessors) - typically 500 or more components on a chip. Later developments include VLSI (Very Large Scale Integration) of integrated circuits 5 years later - typically 10,000 components. The fourth generation is generally viewed as running right up until the present, since although computing power has increased the basic technology has remained virtually the same.

IBM Announced PC, the standard model was sold for $2880. It used the Intel 8088 CPU running at 4.77mhz, containing 5000 transistors. This had 64Kb of RAM, a mono display and the cassette drive was an optional extra. Two 160Kb single sided floppy drives could be added. The machines success was largely due to the openness of its specification, anyone could produce new and improved parts or models of the computer - the original IBM PC usually had an INTEL processor, Tandon disk drives and an operating system from Microsoft. 100,000 orders were taken by Christmas. The first one sold in the U.K. cost £2080. An option of operating systems was actually available, but IBM/Microsofts PC-DOS was by far the cheapest at $39.95.

In 1982 Commodore 64 released, costing just $595. The price rapidly dropped, creating a price war and causing the departure of numerous companies from the home computing market. Total C-64 sales during its lifetime are estimated at more than 20 million units, making it the best-selling computer model of all time.

In 1983 Apple introduced its Lisa. The first personal computer with a graphical user interface, its development was central in the move to such systems for personal computers. The Lisas sloth and high price ($10,000) led to its ultimate failure. The Lisa ran on a Motorola 68000 microprocessor and came equipped with 1 megabyte of RAM, a 12-inch black-and-white monitor, dual 5 1/4-inch floppy disk drives and a 5 megabyte Profile hard drive. The Xerox Star -- which included a system called Smalltalk that involved a mouse, windows, and pop-up menus -- inspired the Lisas designers.

In 1984 Apple Macintosh released.

Applications that came as part of the package included MacPaint, which made use of the mouse, and MacWrite, which demonstrated WYSIWYG (What You See Is What You Get) word processing.

In 1985 Microsoft Windows launched. Not really widely used until version 3, released in 1990, Windows required DOS to run and so was not a complete operating system (until Windows 95, released on August 21, 1995). It merely provided a G.U.I. similar to that of the Macintosh, in fact so similar that Apple tried to sue Microsoft for copying the look and feel of their operating system. This court case was not dropped until August 1997.

Fifth Generation (1990’s – present)

It’s hard to define the borders of the generations, but there exists such computers, what satisfy the criterion of the fifth generation computers.

The program used to create the fifth generation computers was published in 1981 in Japan. The characteristics of these computers:

Building of knowledge base, learning and implication ability, etc.

User-orientated communication: speaking and figure recognition etc.

Artificial Intelligence

Hungarians in Informatics

John Von Neumann: (1903-1957) Von Neumann was the father of game theory and published the classic book Theory of Games and Economic Behavior with Oskar Morgenstern in 1944. He conceived the concept of "MAD" (mutually assured destruction), which dominated American nuclear strategy in the Cold War. He worked in the Theory division at Los Alamos along with Hans Bethe and Victor Weisskopf during World War II as part of the Manhattan Project to develop the first atomic weapons. In 1944 Von Neumann becomes involved in the project, and he suggested that the computer program should actually be stored electronically inside the computer. This was the final breakthrough in computer design, because it meant not only that the computer program could be executed at a speed limited only by the electronic logic of the computer (rather than the mechanical limitation imposed by the card or paper tape reader) but also that computer programs could be designed to take decisions based upon the result of their processing, and modify their actions accordingly. This was possible because the instruction execution sequence could be instantaneously modified since all instructions were equally accessible within the internal computer memory. Furthermore, computer programs could call up other computer programs immediately if required (subject to the constraint that all programs could fit in the computer memory at the same time), and programs could modify other programs or themselves, to improve their processing beyond the bounds of imagination of their human creator. Von Neumann’s idea, the concept stored program control, a very profound one and, more than any other person, he was responsible for computing as we know it today. Von Neumann gave his name to the von Neumann architecture used in most non-parallel-processing computers, because of his publication of the concept, though many feel that this naming ignores the contribution of J. Presper Eckert and John William Mauchly who worked on the concept during their work on ENIAC. Virtually every commercially available home computer, microcomputer and supercomputer is a von Neumann machine. He created the field of cellular automata without computers, constructing the first examples of self-replicating automata with pencil and graph paper. The term von Neumann machine also refers to self-replicating machines. Von Neumann proved that the most effective way large-scale mining operations such as mining an entire moon or asteroid belt can be accomplished is through the use of self-replicating machines, to take advantage of the exponential growth of such mechanisms.

 

John G. Kemény: In 1964 a team leaded by him created BASIC at Dartmouth University. It’s a simple interpreted programming language designed for teaching beginners. BASIC was the firs language made available for personal computers (Microsoft started its business selling a version) and in recent years it has returned importance as Visual Basic, though the later bears little resemblance to earlier versions.

Kozma László (1902-1983): electrical engineer, in 1939 in Antwerpen built relay based machine (jelfogós gép) what was suited for the execution of the 4 basic operations.

Norbert Wiener (November 26, 1894 - March 18, 1964) was an American mathematician, known as the founder of cybernetics. He created the term in his book Cybernetics or Control and Communication in the Animal and the Machine (MIT Press, 1948), widely recognized as one of the most important books of contemporary scientific thinking.

During World War II his work on gunnery control encouraged him to synthesize his interests in communication theory into cybernetics. After the war, his prominence guaranteed him enough clout to arrange for some of the brightest young researchers in artificial intelligence, computer science, and neurophysiology to join him at MIT; then, suddenly and inexplicably, he broke off all contact with the members of this painstakingly assembled research team. Speculation still flourishes as to the reasons why; whether they were professional, or related to his hypersensitive personality. Whatever the reason, it led to the premature end of one of the most promising scientific collaborative research teams of the era.

 

3. Etiquette, juidicary rules related to informatics

 

The copyright secures the literary, scientific and art creations, so the creations, which are related to informatics are also the part of this.

However there are also programs, what you can use freely (freeware, shareware)

There are people, who get the program in an illegal way. That means, he doesn’t buy it, he get it from his friend and he copy it. In that case, not just the second, but the first person is also guilty.

 

Advantages of using a legal software:

-you get a documentation of the program, which tells you important information, the guarantee reparation, the change of the program or a telephone number, what you can call, if a problem occures

-upgrade of the program

-you can avoid the damages, what the viruses can cause

-when you buy the program you acknowledge the value of the work, what the programmers did, and you secure financial opportunity for the programmers to make better the software

 

The proof of the legal software usage:

You can prove, that you are using a legal softvare, with a license contract, which nowadays have a hologram or a security signal. We have to keep this card with us. It includes:

-on how many computer can you use the program(mostly one, sometimes you can use it on PC and on Laptop too)

-how many copies can you make of a program(mostly nothing, but sometimes one for safety)

If somebody deals with an illegal software:

-he can go to court

-he is forbidden from other not legal softwares

- the destuction of the illegal program

-the reimbursement of the legal owner’s damage(jogtulajdonos kárának megtérítése)

When somebody have more versions, then he must use only one version and he must use only the English or the Hungarian one

 

Original or upgrade user right

 

Upgrade is when we buy a computer program, which is kind of the same like our previous software. The are different solutions:

-we have bought our extant program’s modern version

-we have bought the same company’s more modern, but a different kind of product

-we have bought a competitor company’s product

Most of the upgrade program’s are the 60% of the original one.However when you have to prove, that you have the modern version, you have to show the original’s copyright contract.

 

OEM (Original Equipment Manufacturer) version

You can buy OEMs mostly for operation systems. You can only get this version for a complett computer(motherboard, processor, winchester). When we buy a new computer, then we can buy the op system’s OEM version.

 

LP (License Packet)

When we want to use the program on another computer, we buy the LP. In this case we get a user license.

OL (Open license)

Mostly bigger companies, like Microsoft, Novell, Corel, Symantech use it. When you buy a software you get a certain amount of points. After a while, when you have reached a level, 20-30% will go off from the original price. When we buy an open license, the only thing, what we get is a user license.

 

Using the program at home

Some program’s license allows you to use them at your office, and at your home too.

 

Competitor’s right

More people can use the program, but just one at a time.

 

Anonim user right

When you buy a program get a nameless user right, but after you loose it, you can’t prove that the software is original. On the other hand, if you buy the a license contzract, which includes your name, then it is registrated. When you buy more products, like an Open License, you can get it.

 

Shareware: You don’t have to buy it. You only have to pay for the price of the data medium. You will get the restricted version of the program. You can get them from the Internet, or in a computer magazine. If you are satisfied with the shareware version, you don’t have to, but if it is time limited, you must buy the original one.

 

Freeware: You can download it, or it is on a CD ROM. You can freely copy it and give it to others.

 

4. Info tétel: Ismertesse az adatábrázolást, adattárolás módját a számítógépekben!

• Mit neveznek adatnak? Soroljon fel példákat!
• Mit neveznek információnak? Soroljon fel példákat!
• Mi a kapcsolat az adat, a jel, az információ között?
• Milyen számjegyeket használnak a kettes számrendszerben?
• Mi a bit és a bájt fogalma? Mi a kapcsolat közöttük?
• Ismertesse a bináris karakterábrázolás módját!
• Hogyan tudna elektronikus levelet küldeni tanárának?

 

 

Data: Data are the appearance (in letters, numbers, punctuation marks, words) of some kind of fact, idea, news what we can measure, store, process and send on.

For example: the age of a person, the weather today, the color of a pencil

 

Information: Information is the meaning of data, or the news it contains for us. Data contains information for us if we can understand it and it’s important and new to us.

In other words information is the product of the thinking, over perceived data, so information is interpreted data.

For example: The news of the delay because of the bad weather makes the people nervous who wanted to fly that day. The people who will fly on the next week won’t care.

 

To be understandable the data must meet the requirements for its content and form.

The whole of the formal rules are called syntax.

The whole of the content rules are called semantic.

 

Data must be transformed for the forwarding. This process is called coding. In this process we transform data to signs which can be forwarded. This way signs carry data, and if the communication is successful the information within.

 

For the description of characters on a digital computer we use the signs of the binary system. The binary digits are 0 and 1, each of them means one bit.

The bit is the smallest unit of information. For the storage of a coded character we use 8 bits= 1 byte. The computers can work with 1 byte or with it’s multiple at once, so the smallest amount of available information is 1 byte.

 

The properties of the binary system:

• The base number of the system is 2.
• The number of the digits is 2.
• The binary digits are 0 and 1.
• The sum of the powers of 2 multiplied with 0 and 1 gives the value of the number: 110010.01₂=1×2⁵+1×2⁴+0×2³+0×2²+1×2¹+0×2⁰+0×2^-1+1×2^-2

 

This has great advantages, because you can skip the multiplication with 0 and you basically don’t need to calculate the multiplication with 1.

These properties are greatly contributed to that today’s computers are built from digital circuits with two states, and use the binary system.

 

We can clearly see that in n bits we can store 2ⁿ type of data, and if we write these as numbers smallest number is 0, while the greatest is 2ⁿ-1.

So in one byte we can store 2⁸=256 type of data in a domain of 0-255.

For the smallest storage units we use 2 bytes (word) or 4 bytes (double word), while for larger storage units we use a million times greater units.

2¹⁰ byte = 1024 byte = 1KB

1024KB = 1MB

1024MB = 1GB

1024GB = 1TB

 

To understand the storage of data on computers we must see that we have to store a lot of type of data, and computers store and work with data in binary digit form.

Computers store programs in a similar way as data. Programs consist of commands, and commands consist of numbers which symbolize their operation. For the storage of programs computers use the rules of the binary system, and usually store programs in forms of 8 bit numbers.

Computers store texts as characters. Characters are letters, numbers, punctuation marks and other symbols. The base of character storage is a character set (kódtábla) which renders a (code) number to each character. For the storage the computer uses this number, not the character. The code of every character is a 1 byte number, which means we can store 256 types of characters on the computer. In a standard situation this is enough for the storage of letters, numbers, punctuation marks and other symbols. Computers use the ASCII (American Standard Code for Information Interchange) character set. You can find most of the common characters in this character set, and the numbers rendered to the characters are called ASCII-codes.

Logical type of data can take two values. The „yes” and „no” values are stored as 1 and 0 on computers in 1 byte.

There are numerous methods and standards for the storage of pictures and sounds. A picture or sound can take more megabytes of storage, depending on its quality. Coptures also store pictures and sounds in the form of binary digits.

 

Draw up the set up of the Neumann computer and explain shortly the functions of the units!

 

The computer builds up functionally five units:

• Input unit, through which we can get data into the computer and can also encroach the functioning of it,
• Storage unit, in which we store the data got through the input unit or the results of the calculations,
• Calculator unit, which performs various arithmetic and logic operations with the stored data on the computer,
• Output unit, by which we can visualize the results of the processing,
• Control unit, which controls the functioning of all the listed units.

 

 

What is the CPU and what are the parts of it?

CPU: Central Processing Unit

The CPU consists of the following parts:

• CU: Control Unit
• ALU: Arithmetic and Logic Unit
• Cache: Fast inside storage

 

CU: The control unit coordinates the steps necessary to execute each instruction. It causes each instruction to be moved to the CPU and then decodes it so that it can be executed. It then tells the other parts of the CPU what to do and when to do it.

ALU: The Arithmetic and Logic unit is responsible for doing the actual computing and so can be considered to be the brain of the computer. As far as arithmetic is concerned, it has a very limited repertoire basically being confined to addition and subtraction (multiplication is repeated addition and division is repeated subtraction). It can however, perform these operations at very high speed. It also contains the registers which are a number of small, high speed memories.

Cache: Speeds up the data traffic between the CU and the Storage device, by which also speeds up the functioning of the whole computer.

Which are the most important parameters of the memories? How do we measure them?

The two most important parameters of the memories are the following:

• The size of its capacity
• The time of the accessing

 

The size of the capacity means: How much data can it contain?
We measure it in bytes: bytes, Kbytes, Mbytes, Gbytes …etc

The time of accessing means the time period between the assignment and the data transfer.

We measure it bye time: ns (nanosec) and ms (milisec)

 

How do we group the memories by the aspect of accessing and writing?

 

By accessing we can make difference between:

• Serial Acces Memory
• RAM: Random Acces Memory

 

The feature of the Serial Storage is that the specific data can be read only if the previous data has just been read before it. It is called streaming. The accessing time depends on which data we need according to the order of the memory.

The feature of the RAM is that the accessing time does NOT depend on the order of the memory.

 

By writing we can make difference between:

• ROM: Read Only Memory
• RWM: Read-Write Memory

 

The ROMs are fix memories, the data can only be read and cannot be changed. These memories stores the data in case of loosing voltage (turning off the computer), too.

The user can write, change and delete data in the RWMs. At these memories, voltage is needed to store the data. So if we loose voltage or turn off our computer the stored data looses.

 

Introduce the in- and output devices of a mainboard (motherboard)!

Serial & Parallel

The communications links may be either serial or parallel. A parallel link transmits several streams of data (perhaps representing particular bits of a stream of bytes) along multiple channels (wires, printed circuit tracks, optical fibres, etc.); a serial link transmits a single stream of data.

 

Serial ports: basic serial port, PS2, USB, COM

Parallel port: LPT (mostly older printers use it)

 

 

Motherboard buses:

PCI: The Peripheral Component Interconnect standard (in practice almost always shortened to PCI) specifies a computer bus for attaching peripheral devices to a computer motherboard.

AGP: The Accelerated Graphics Port (also called Advanced Graphics Port) is a high-speed point-to-point channel for attaching a single device (generally a graphics card) to a computers motherboard, primarily to assist in the acceleration of 3D computer graphics.

 

Explain the function of the computer chassis and the power supply!

Chassis: locks the parts
lowers the noise
saves against dirt, wet, hit

Power supply: The parts of the computer need a lot of many voltages: 12V, 5V, 3.3V
The mainboard gets these voltages from the power supply.
The power supply also has to keep the main voltage on 12V.

 

6.   Ismertesse és jellemezze a számítógépek bemeneti perifériáit!

• Ismertesse a billentyűzet részeit!
• Miért és mire használjuk az egeret?
• Ismertesse az egerek típusait!
• Mi a szkenner és mire használjuk?

 

• Keyboard
• Mouse
• Scanner

 

Keyboard

• Functionkeys – run different assignments in different prorams. Usually starts a new program
• Esc(ESCape) we can stop applications or exit from the programs
• Typing keys
  • It covers the letters, numbers(over the letters) and signs
  • We can also find here the CAPitalS LOCK, ENTER, BACKSPACE, TABULATOR, and the WINDOWS sign(sometimes the mouse’s right button)
  • We want to be capital:
    • Every letter: push the CAPS LOCK(if it’s on, the SHIFT key changes the letters to non-capital)
    • Few letter: push SHIFT
  • Types:
    • Hungarian (QWERTZ)
    • Eglish(instead of the „É” letter stands „;” etc.)
  • Another alignment:
    • 101 buttons (there isn’t „í” letter) (there isn’t WINDOWS button)
    • 102 (there’s „í” letter) (there isn’t WINDOWS button)
    • 104 (there isn’t „í” letter) (there’s WINDOWS button)
    • 105 (there’s „í” letter) (there’s WINDOWS button)
  • If we want signs(’ „ + etc.) push SHIFT and the number
  • We can sign in WIN when we push CTRL+moving key, SHIFT+mvgk
  • ASCII letters: push AltGR and the numbers, which we can find on the numerical, right part
  • Display LEDs(active, when we push NUM LOCK, SCROLL LOCK or CAPS LOCK)
  • Cursor-moving keys
  • Numerical keys
  • The ENTER
    • runs an application in MS-DOS
    • new paragraph
    • choosing
  • With Backspace we can clear letters from right to left
  • HOME, END, PAGE UP/DOWN, DELETE, INSERT, we can erase, jump, PRINT SCR, SCRLOCK, PAUSE(we can stop the display for a while)
  • TABULATOR has no role in MS-DOS, just in WIN, where we can jump between boxes etc.

Mouse

• As an input device, we can use mouse on graphical user’s devices(WIN, LINUX)
• The phisically moving on the desk of the mouse makes the mouse-coursor move the same side with the same speed
• We can start an operation clicking to an object(text, pic)
• We can also sign a piece of text using SHIFT or CRTL(sometimes ALT also..) and left clicking on the text
• Complex using
• Another use:

1. 1. play
2. 2. draw
3. 3. easyer attainment of documents

• Types:
  • Mechanical mouse
  • Optical mouse
  • Track bal
  • Touch pad(laptops, notebooks)
  • Different types, different number of buttons on the mouse
  • Another grouping:
    • PS2
    • Serial port
    • USB
    • Wireless / radiowave
    • Nowadays  utmost user use optical mouse

Scanner

• With scanner, we can take pictures with electonic form into the computer
• In use: the data on the paper will be scanned in optcial way and the computer makes a copy of it into the computer’s operative store.
• Picture processor-programz
• Computer makes pixels of the picture, not characters
• When we scan a page with handwrite, the scanner makes pixels of it
• OCR (Optical Character Recognize) is an accessory of the scanner, which recognizes the text

7. Output devices

Computer Monitors

Visual Display Units (VDU) or monitors are used to visually interface with the computer and are similar in appearance to a television.

A cathode ray monitor

A plasma monitor

Visual Display Units display images and text which are made up of small blocks of coloured light called pixels. The resolution of the screen improves as the number of pixels is increased. Most monitors have a 4:3 width to height ratio.

The computer monitor is an output device that is part of your computers display system. A cable connects the monitor to a video adapter (video card) that is installed in an expansion slot on your computer’s motherboard. This system converts signals into text and pictures and displays them on a TV-like screen (the monitor).

The computer sends a signal to the video adapter, telling it what character, image or graphic to display. The video adapter converts that signal to a set of instructions that tell the display device (monitor) how to draw the image on the screen.

Cathode Ray Tube (CRT)
The CRT, or Cathode Ray Tube, is the "picture tube" of your monitor. Although it is a large vacuum tube, its shaped more like a bottle. The tube tapers near the back where theres a negatively charged cathode, or "electron gun". The electron gun shoots electrons at the back of the positvely charged screen, which is coated with a phosphorous chemical. This excites the phosphors causing them to glow as individual dots called pixels (picture elements). The image you see on the monitors screen is made up of thousands of tiny dots (pixels). If youve ever seen a childs LiteBrite toy, then you have a good idea of the concept. The distance between the pixels has a lot to do with the quality of the image. If the distance between pixels on a monitor screen is too great, the picture will appear "fuzzy", or grainy. The closer together the pixels are, the sharper the image on screen. The distance between pixels on a computer monitor screen is called its dot pitch and is measured in millimeters. (see sidebar). You should try to get a monitor with a dot pitch of .28 mm or less.

Note: From an environmental point of view, the monitor is the most difficult computer peripheral to dispose of because of the lead it contains.

There are a couple of electromagnets (yokes) around the collar of the tube that actually bend the beam of electrons. The beam scans (is bent) across the monitor from left to right and top to bottom to create, or draw the image, line by line. The number of times in one second that the electron gun redraws the entire image is called the refresh rate and is measured in Hertz (Hz).
If the scanning beam hits each and every line of pixels, in succession, on each pass, then the monitor is known as a non-interlaced monitor. A non-interlaced monitor is preferred over an interlaced monitor. The electron beam on an interlaced monitor scans the odd numbered lines on one pass, then scans the even lines on the second pass. This results in an almost imperceivable flicker that can cause eye-strain.

 

This type of eye-strain can result in blurred vision, sore eyes, headaches and even nausea. Dont buy an interlaced monitor, they can be a real pain in the ... ask your optometrist.

Interlaced computer monitors are getting harder to find (good!), but they are still out there, so keep that in mind when purchasing a monitor and watch out for that "steal of a deal".

Video Technologies
Video technologies differ in many different ways. However, the major 2 differences are resolution and the number of colors it can produce at those resolutions.

Resolution
Resolution is the number of pixels that are used to draw an image on the screen. If you could count the pixels in one horizontal row across the top of the screen, and the number of pixels in one vertical column down the side, that would properly describe the resolution that the monitor is displaying. It’s given as two numbers. If there were 800 pixels across and 600 pixels down the side, then the resolution would be 800 X 600. Multiply 800 times 600 and you’ll get the number of pixels used to draw the image (480,000 pixels in this example). A monitor must be matched with the video card in the system. The monitor has to be capable of displaying the resolutions and colors that the adapter can produce. It works the other way around too. If your monitor is capable of displaying a resolution of 1,024 X 768 but your adapter can only produce 640 X 480, then that’s all you’re going to get.
When we talk about the different technologies, we’re talking about the video card and monitor that make up that display system. Also, standards describe the basic number of colors and resolutions for each technology, but individual manufacturers always take liberties, providing options and enhancements that are designed to make their product more appealing to the end user. This is, of course, how new standards come about.

Monochrome
Monochrome monitors are very basic displays that produce only one color. The basic text mode in DOS is 80 characters across and 25 down. When graphics were first introduced, they were fairly rough by todays standards, and you had to manually type in a command to change from text mode to graphics mode. A company called Hercules Graphics developed a video adapter that could do this for you. Not only could it change from text to graphics, but it could do it on the fly whenever the application required it. Today’s adapters still basically use the same methods.

CGA/EGA
The Color Graphics Adapter (CGA) introduced color to the personal computer. In APA mode it can produce a resolution of 320 X 200 and has a palette of 16 colors but can only display 4 at a time. With the introduction of the IBM Enhanced Graphics Adapter (EGA), the proper monitor was capable of a resolution of 640 X 350 pixels and could display 16 colors from a palette of 64.

VGA
Up until VGA, colors were produced digitally. Each electron beam could be either on or off. There were three electron guns, one for each color, red, green and blue (RGB). This combination could produce 8 colors. By cutting the intensity of the beam in half, you could get 8 more colors for a total of 16. IBM came up with the idea of developing an analog display system that could produce 64 different levels of intensity. Their new Video Graphics Array adapter was capable of a resolution of 640 X 480 pixels and could display up to 256 colors from a palette of over 260,000. This technology soon became the standard for almost every video card and monitor being developed.

 

SVGA
Once again, manufacturers began to develop video adapters that added features and enhancements to the VGA standard. Super-VGA is based on VGA standards and describes display systems with several different resolutions and a varied number of colors. When SVGA first came out it could be defined as having capabilities of 800 X 600 with 256 colors or 1024 X 768 with 16 colors. However, these cards and monitors are now capable of resolutions up to 1280 X 1024 with a palette of more than 16 million colors.

XGA
Extended Graphics Array was developed by IBM. It improved upon the VGA standard (also developed by IBM) but was a proprietary adapter for use in Micro Channel Architecture expansion slots. It had its own coprocessor and bus-mastering ability, which means that it had the ability to execute instructions independent of the CPU. It was also a 32-bit adapter capable of increased data transfer speeds. XGA allowed for better performance, could provide higher resolution and more colors than the VGA and SVGA cards at the time. However, it was only available for IBM machines. Many of these features were later incorporated by other video card manufacturers.

PRINTERS

You can print out information that is in the computer onto paper. By printing you create what is known as a hard copy.
There are different kinds of printers which vary in their speed and print quality.

The two main types of printer are impact and non-impact.

Impact Printer

Impact Printers use a print head containing a number of metal pins which strike an inked ribbon placed between the print head and the paper.

An impact printer showing detail of print head

Some print heads have only 9 pins to make the dots to build up a character; some have 24 pins which produce a better resolution.

Dot Matrix Printer

 

Characters are formed from a matrix of dots.
The speed is usually 30 - 550 characters per second (cps). This is the cheapest and noisiest of the printer family. The standard of print obtained is poor.

A dot matrix printer

These printers are cheap to run and relatively fast. They are useful for low quality carbon copy printing.

Ink Jet Printers

Characters are formed as a result of electrically charged or heated ink being sprayed in fine jets onto the paper. Individual nozzles in the printing head produce high resolution (up to 400 dots per inch or 400 dpi) dot matrix characters.

Inkjet printers use colour cartridges which combine magenta, yellow and cyan inks to create colour tones. A black cartridge is also used for crisp monochrome output.

This method of printing can generate up to 200 cps and allows for good quality, cheap colour printing.

 

Daisywheel Printer

Molded metal characters like those in a typewriter are mounted on extensions attached to a rotating wheel and are printed onto the paper by means of a hammer and print ribbon.

A daisy wheel showing detail of the characters

This results in a great deal of movement and noise during the printing of documents, so printing is slow (less than 90 cps).
The standard of print is similar to that produced by an electric typewriter. As the characters on the wheel are fixed, the size and font can only be changed by using a different wheel. However, this is very rarely done.

Non-Impact Printers

Thermal Printers

Characters are formed by heated elements being placed in contact with special heat sensitive paper forming darkened dots when the elements reach a critical temperature.

A fax machine uses a thermal printer

Thermal printer paper tends to darken over time due to exposure to sunlight and heat. The standard of print produced is poor.

Thermal printers are widely used in battery powered equipment such as portable calculators.

Laser Printer

Laser Printers use a laser beam and dry powdered ink to produce a fine dot matrix pattern. This method of printing can generate about 4 pages of A4 paper per minute.

A laser printer

The standard of print is very good and laser printers can also produce very good quality printed graphic images too.

How It Works

A photoconductive drum is initially charged and then a high intensity laser beam is used to discharge selected areas on the drum. These discharged areas correspond to the white areas of the printed document.

Toner is attracted to parts of the drum with a high charge. The drum rotates and transfers the toner to the paper which has an even greater electrical charge. Finally a heater fixes the toner onto the paper.

How a laser printer works

OTHER OUTPUT DEVICES

Robots

Robots are able to perform a variety of tasks as a result of executing instructions contained within a program.

We are still a long way from the science fiction robots and androids portrayed by the film industry.

A robot arm

Robots in a business sense mean automated machines designed to perform mundane operations which require accuracy, such as assembling cars.

They are seldom manufactured to resemble the human form.

Machine Tool

Computer Aided Manufacturing (CAM) tools are used to manufacture a variety of products.

Repetitive functions are controlled by sets of computer instructions.

Machine tools automate factory production and have the advantage over humans of high accuracy, and they never require a coffee break!

Voice

Voice synthesis has a robotic sound due to the difficulties of replicating the complexities of human speech and pronunciation.

Voice answer back (VAB) is used to respond to telephone enquiries, such as the speaking clock.

A speak and spell toy

Educational applications include "Speak & Spell" and arithmetic trainers.

 

Plotters

Plotters are used to produce graphs or diagrams.
Plotters can be of two types:

• Pen plotters
• Electrostatic plotters

Pen plotters have an ink pen attached to draw the images, and electrostatic plotters work similarly to a laser printer.

Flatbed Plotter

This is a plotter where the paper is fixed on a flat surface and pens are moved to draw the image. This plotter can use several different colour pens to draw with.

The size of the plot is limited only by the size of the plotters bed.

Top view of a flat bed plotter

Drum Plotters

In drum plotters the pen is moved in a single axis track and the paper itself moves on a cylindrical drum to add the other axis or dimension.

A drum plotter

The size of the graph is therefore limited only by the width of the drum and can be of any length.

Electrostatic Plotter

An Electrostatic Plotter produces a raster image by charging the paper with a high voltage.

This voltage attracts toner which is then melted into the paper with heat.

This type of plotter is fast, but the quality is generally considered to be poor when compared to pen plotters.

Computer monitors

Monochrome

CGA/EGA

VGA

SVGA

XGA

Printers

Impact Printer

Dot Matrix Printer

Daisywheel Printer

Ink Jet Printers

Non-Impact Printers

Thermal Printers

Laser Printer

OTHER OUTPUT DEVICES

Robots

Machine Tool

Voice

Flatbed Plotter

Drum Plotters

Electrostatic Plotter

 

 

 

 

 

Reading/Writing:

Writing is the process when the laser is burning pits on the surface of the optical storage disc.

Writing is the process when the head is magnetizing the plate of the magnetical carrier surface.

Reading is the process when the laser is checking the surface if there is a pit (1) or not (0).

Reading is the process when the head is checking if there is a magnetic charge (1) or not (0).

 

Computer Storage Devices used nowadays

Type	FD	HD	CD	DVD	FLASH MEMORY
Size	1,44MB	2,1GB - 400GB	700MB	4,5GB	up to 4 GB
Seek Time	slow	<20ms	<150ms	<200ms	<5μs

 

FD

Inexpensive lightweight removable disk with a limited storage capacity (storage capacity up to about 2 Mbytes [1996]) for a personal computer used to store and retrieve data. It consists of a flexible (floppy) disk coated with magnetic oxide surrounded by a hard plastic case.

HD

Auxiliary random-access magnetic memory. It contains one or more platters covered with magnetic material on which data can be written or read by means of read-write heads that can move in and out while the platters are spinning. Typical storage capacity for a personal computer is about 40 G byte.

CD

Compact disk: high-capacity storage device in which the data (sound, images, and computer data) are stored (mostly only once) by burning small holes and from which data are repeatedly retrieved by means of a laser beam.

 

DVD

DVD is an optical disc storage media format that can be used for storing data, including movies with high video and sound quality. DVDs resemble compact discs: their physical dimensions are the same—12cm or the mini 8cm—but they are encoded in a different format and at a much higher density. Unlike CDs, all DVDs must contain a file system. This file system is called UDF, and is an extension of the ISO 9660 Standard used for Data-CDs.

FLASH MEMORY

Flash memory is a form of EEPROM that allows multiple memory locations to be erased or written in one programming operation. In lay terms, it is a form of rewritable memory chip that, unlike a Random Access Memory chip, holds its content without maintaining a power supply.

 

9. Operating systems

The most important program that runs on a computer. Every general-purpose computer must

have an operating system to run other programs. Operating systems perform basic tasks, such as

recognizing input from the keyboard, sending output to the display screen, keeping track of files and

directories on the disk, and controlling peripheral devices such as disk drives and printers.

For large systems, the operating system has even greater responsibilities and powers. It is like a

traffic cop -- it makes sure that different programs and users running at the same time do not

interfere with each other. The operating system is also responsible for security, ensuring that

unauthorized users do not access the system.

Operating systems can be classified as follows:

multi-user: Allows two or more users to run programs at the same time. Some operating systems

permit hundreds or even thousands of concurrent users.

multiprocessing: Supports running a program on more than one CPU.

multitasking: Allows more than one program to run concurrently.

multithreading: Allows different parts of a single program to run concurrently.

real time: Responds to input instantly. General-purpose operating systems, such as DOS and UNIX,

are not real-time.

Operating systems provide a software platform on top of which other programs, called application

programs, can run. The application programs must be written to run on top of a particular operating

system. Your choice of operating system, therefore, determines to a great extent the applications you

can run. For PCs, the most popular operating systems are OS/2, and Windows, but others are

available, such as Linux.

As a user, you normally interact with the operating system through a set of commands. For example,

the DOS operating system contains commands such as COPY and RENAME for copying files and

changing the names of files, respectively. The commands are accepted and executed by a part of the

operating system called the command processor or command line interpreter. Graphical user

interfaces (GUI) allow you to enter commands by pointing and clicking at objects that appear on the

screen.

In general, the operating system is the first layer of software loaded into computer memory when it

starts up. As the first software layer, all other software that gets loaded after it depends on this

software to provide them with various common core services. These common core services include,

but are not limited to: disk access, memory management, task scheduling, and user interfacing.

Since these basic common services are assumed to be provided by the OS, there is no need to reimplement

those same functions over and over again in every other piece of software that you may

use. The portion of code that performs these core services is called the kernel of the operating

system. Operating system kernels had been evolved from libraries that provided the core services

into unending programs that control system resources because of the early needs of accounting for

computer usage and then protecting those records.

1 Operating systems

Operating systems

Common core services

As operating systems evolve, ever more services are expected to be common core. These days, an

OS may be required to provide network and Internet connectivity. They may be required to protect

the computers other software from damage by malicious programs, such as viruses. The list of

common core services is ever expanding.

Programs communicate with each other through Application Programming Interfaces, or APIs,

similar to how humans interact with programs through User interfaces. This is especially true

between application programs and the OS. The OSs common core services are accessed by

application programs through the OSs APIs. Thus an OS enables the communication between

hardware and software. CPU scheduling is also a main function of the operating system.

Todays operating systems

As of 2005, the major operating systems in widespread use on general-purpose computers

(including personal computers) have consolidated into two families: the Unix-like family and the

Microsoft Windows family. Mainframe computers and embedded systems use a variety of different

operating systems, many with no direct connection to Windows or Unix.

The Unix-like family is a more diverse group of operating systems, with several major subcategories

including System V, BSD, and Linux. The name "Unix" is a trademark of The Open

Group which licenses it for use to any operating system that has been shown to conform to the

definitions that they have cooperatively developed. The name is commonly used to refer to the large

set of operating systems which resemble the original Unix. Unix systems run on a wide variety of

machine architectures. Unix systems are used heavily as server systems in business, as well as

workstations in academic and engineering environments. Free software Unix variants, such as Linux

and BSD are increasingly popular, and have made inroads on the desktop market as well. Apples

Mac OS X, a BSD variant, has replaced Apples earlier (non-Unix) Mac OS in a small but dedicated

market, becoming one of the most popular Unix systems in the process.

The Microsoft Windows family of operating systems originated as a graphical layer on top of the

older MS-DOS environment for the IBM PC. Modern versions are based on the newer Windows NT

core that first took shape in OS/2. Windows runs on 32- and 64-bit Intel and AMD computers,

although earlier versions also ran on the DEC Alpha, MIPS and PowerPC architectures (and there

was work in progress to make it work also on the SPARC architecture). Today, Windows is a

popular desktop operating system, enjoying a near-monopoly of around 90% of the worldwide

desktop market share. It is also widely used on low-end and mid-range servers, supporting

applications such as Web servers and database servers.

Mainframe operating systems, such as IBMs z/OS, and embedded operating systems such as QNX,

eCos, and PalmOS, are usually unrelated to Unix and Windows.

Older operating systems which are still used in niche markets include the Windows-like OS/2 from

IBM; VMS from Hewlett-Packard (formerly DEC); Mac OS, the non-Unix precursor to Apples

Mac OS X; and AmigaOS, the first GUI based operating system with advanced multimedia

capabilities available to the general public.

2 Operating systems

Operating systems

Classifications and terminology

An operating system is conceptually broken into three sets of components: a user interface (which

may consist of a graphical user interface and/or a command line interpreter or "shell"), low-level

system utilities, and a kernel--which is the heart of the operating system. As the name implies, the

shell is an outer wrapper to the kernel, which in turn talks directly to the hardware.

Hardware <-> Kernel <-> Shell <-> Applications

In some operating systems the shell and the kernel are completely separate entities, allowing you to

run varying combinations of shell and kernel (eg UNIX), in others their separation is only

conceptual.

Kernel design ideologies include those of the monolithic kernel, microkernel, and exokernel.

Traditional commercial systems such as UNIX and Windows (including Windows NT), and the

newer Linux, use a monolithic approach, while the trend in more modern systems is to use a

microkernel (such as in AmigaOS, QNX, BeOS, Mac OS X etc). The microkernel approach is also

very popular among research OSs. Many embedded systems use ad hoc exokernels.

3 Operating systems

 

 

COPY	Copies selected information and makes a duplicate to the given location
MOVE	Removes selected information from its current location and takes it to the given location

Deleting Files and Folders

 

Under the default settings, objects deleted from your computers hard drives go to the Recycle Bin, from which they can be recovered. You can reset your preferences so objects are deleted immediately and dont go to the Recycle Bin. Objects deleted from floppy drives or other removable disks dont go to the Recycle Bin

• select the objects to be deletedà  click to the “File” section on the menu barà select “Delete”à click “Yes” in the dialog box
• select the objects to be deleted à right-click on the selected filesà choose “Delete” from the popup submenuà click “Yes” in the dialog box
• select the objects to be deleted à press DELETEà click “Yes” in the dialog box

You can delete files or folders directly, without sending them to the Recycle Bin: to delete a file or folder immediately, select it, press SHIFT+DELETE, and then click Yes when the confirmation box appears.

What Do the Parts of Windows Do?

The window is a rectangular area on the screen that displays information from a running program.

Although whats inside the window frame changes from program to program, most windows you see in Windows include the following components:

System Menu button	Displays a menu of commands you can use to move and resize your window.
Title bar	Displays the title of the window and provides a way to move the window around within the screen.
Minimize button	Shrinks the window to an icon on the taskbar.
Maximize or Restore button	When you click the Maximize button, the window expands to cover the whole screen. Once a window has been maximized, the Maximize button disappears and is replaced by the Restore button. When you click the Restore button (with two overlapping rectangles), the window shrinks to its previous size and the Maximize button reappears.
Close button	The upper right corner of a window which closes the window and exits the program.
Menu bar	Provides a row of menus you can use to choose commands.
Toolbar	Provides a row of buttons you can click to give commands.
Status bar	Displays information about the program. Some programs enable you to give commands by clicking parts of the status bar.
Scroll bar	Vertical or horizontal bar running along the right side or bottom of a window allowing you to scroll the information displayed in the window.
Window borders	Provide a way to drag around the edges of the window to change the size and shape of the window.

 

11.

Computer science divides software into two major classes: system software and application software.

1.  Application software is a subclass of computer software that employs the capabilities of a computer directly to a task that the user wishes to perform. This should be contrasted with system software which is involved in integrating a computers various capabilities, but does not directly apply them in the performance of tasks that benefit the user. The term application refers to both the application software and its implementation.

A simple, if imperfect, analogy in the world of hardware would be the relationship of an electric light—an application—to an electric power generation plant—the system. The power plant merely generates electricity, itself not really of any use until harnessed to an application like the electric light which performs a service that the user desires.

Typical examples of software applications are word processors, spreadsheets and media players.

2. System software is a generic term referring to any computer software whose purpose is to help run the computer system. Most of it is responsible directly for controlling, integrating, and managing the individual hardware components of a computer system.

System software is opposed to application software that helps solve user problems directly.

Users often see things differently than programmers. People who use modern general purpose computers usually see three layers of software performing a variety of tasks: platform, application, and user software.

1.  Platform includes the basic input-output system, device drivers, an operating system, and typically a graphical user interface which, in total, allow a user to interact with the computer and its peripherals (associated equipment). Platform software often comes bundled with the computer, and users may not realize that it exists or that they have a choice to use different platform software.

 

1. Applications are what most people think of when they think of software. Typical examples include office suites and video games. Application software is often purchased separately from computer hardware. Sometimes applications are bundled with the computer, but that does not change the fact that they run as independent applications. Applications are almost always independent programs from the operating system, though they are often tailored for specific platforms. Most users think of compilers, databases, and other "system software" as applications.

 

1. User software tailors systems to meet the users specific needs. User software include spreadsheet templates, word processor macros, scientific simulations, graphics and animation scripts. Even email filters are a kind of user software. Users create this software themselves and often overlook how important it is.

File extensions

 

There are some basic things you need to understand about file extensions. First, you need to understand what an extension is and and what it is not. Second, you need to understand that its possible your computer is not showing you file extensions and what to do about that.

What is an Extension?

Disk files have to be identified so the operating system can address them. These filenames have specific rules.

The basic form of a filename is:

rootname.ext

The first part of the name to the left of the period is called the root name. The root name cannot be the same as a device name. The second part to the right of the period is the extension. It is optional and is often, but not necessarily, three characters long. Under MS-DOS the rootname could only be eight characters long and the extension no more than three so three characters (or less) is often still the default although under Windows 95 and above that limit is now gone. Some still use three characters for files that must be backward compatible for still-running DOS-based systems.

Fortunately, Windows 95 changed all that by introducing long filenames, and Windows XP retains that advance. File and folder names can be up to 215 characters long, and can include spaces. So jnsdecr.doc can become Johns December Report.doc.

Folders, likewise, can have names up to 215 characters long. These names are automatically of type "folder" and have no extension.

In addition to periods and spaces, some characters that were illegal for file and folder names prior to Windows 95 are now legal, including

+ , ; = [ ]

Still, there are some characters you cant use in filenames, including

\ / : * ? " &la; &ra; |

and any character you make by using the CTRL key.

Image Files:                             BMP Windows or OS/2 bitmap

GIF CompuServe bitmap

JPG JPEG bitmap

JPEG JPEG bitmap

Sound Files:                             MID MIDI music

MP3 MPEG Audio Layer 3 (AC3) file

WAV Windows Waveform sound

Movie Files:                              AVI Microsoft Video for Windows movie

MOV QuickTime for Windows movie

MPG MPEG animation

MPEG MPEG animation

Compressed Files:                  ARJ Robert Jung ARJ compressed archive

ZIP Zip file

RAR

Word Processed Files:           DOC Microsoft Word document

TXT Text

Web Page HTML Files:          HTM, Hypertext document

HTML Hypertext document

 

In searching there is no difference between upper case and lower case letters and the same with the long and the short vowels:

i=í, o=ó, ö=ő, ü=ű

The joker characters are:

* any number of characters follows
? replaces only one character

 



12. Ismertesse az adatkezelés eszközeit!

 

Compression:

Whats compression?

Short Answer: A method of making files smaller on disk.

Long Answer: When Claude Shannon, the father of Information Theory, first posed the question asking how a communication system can efficiently transmit the information that a source produces in the late 1940s, he gave way to an entirely new field of study: data compression. Developments made in this area during the past half century have ignited a communications revolution in recent years. This transformation includes the ever-present, ever-growing Internet; the explosive development of mobile communications; and the ever-increasing importance of video communication. Data compression, which for a long time was the domain of a relatively small group of engineers and scientists, is now ubiquitous for is it one of the enabling technologies for so many aspects of the multimedia revolution. Though the field of data compression is either taken for granted or unrecognized by many, cellular phones, satellite TV, modems, fax machines and many other communication technologies could never have been conceived without it.

File compression such as the familiar ZIP format removes repetitive characters such as spaces and other redundant data from a file and records what it has done in a table of the header record of the file. When the file is uncompressed the table is read and all the removed characters are restored. The logic that tells the zip program how to compress and decompress the file is public domain and small enough to store inside the zip program.

Compression for images is almost the same except that the redundant data are pixels. Movies, which are just a long strip of sequential images use the same process. Sound compression is a bit too complicated to explain here but the theory is the same. The logic used for compression and decompression of a movie or sound is stored in a helper file called a codec. When an author creates a multimedia file it is typically very large. To make it smaller it is compressed using a codec and the identity of the codec is stored in the header of the multimedia file.

Data Compression

How does compression work?

Compression relies on the fact that the data is redundant, that till some extent it was generated following some rules, and that we can learn those rules, and thus predict accurately the data. A compressor can reduce the size of a file by deciding which data is more frequent and assigning it less bits than to less frequent data. Clearly compression has two parts: one guess which are the most frequent symbols, and other which outputs the "decision" of the first one.

Using the right terminology we would say that the first is called a model and that predicts the probability of the source, it then makes a probability distribution. And that the second one is the coder and it makes and emits codes based on the probabilities assigned by the model. The closer that are the predictions made by the model to the data, the more compression we can achieve, because well assign less bits to most of the data.

Immediately the two main questions of data compression arise: which rules should we follow to assign probabilities to the symbols? and given a probability distribution, which are the smallest codes that we can assign? Information theory is a science whose role is to answer these questions.

Lossless Compression: An Overview

Lossless compression techniques, as their name implies, involve no loss of information. If data have been losslessly compressed, the original data can be recovered exactly from the compressed data after a compress/expand cycle. Lossless compression is generally used for so-called "discrete" data, such as database records, spreadsheets, word-processing files, and even some kinds of image and video information.

Text compression is a significant area for lossless compression. It is very important that the reconstruction is identical to the text original, as very small differences can result in statements with very different meanings. Consider the sentences "Do not send money" and "Do now send money." A similar argument holds for computer files and for certain types of data such as bank records.

Furthermore, if data of any kind are to be processed or "enhanced" later to yield more information, it is important that the integrity be preserved. For example, suppose we compressed a radiological image in a lossy fashion, and the difference between the reconstruction Y and the original X was visually undetectable. If this image was later enhanced, the previously undetectable differences may cause the appearance of anomalies that could potentially mislead the radiologist. Because the price for this kind of mishap may be a human life, it makes sense to be very careful about using a compression scheme that generates a reconstruction that is different from the original.

In essence, lossless compression algorithms are needed in cases that require compression where we want the reconstruction to be identical to the original.

Lossy Compression

Lossy compression differs from its counterpart, lossless compression, as its name implies—some amount of data may be lost in the process.  Thus, after a compression/decompression cycle, the data set will be modified from the uncompressed original and information may be lost.

One may ask why the loss of data can be tolerated in any case. Lossy compression techniques attempt to eliminate unnecessary or redundant information, focusing more on saving space over preserving the accuracy of the data. Ideally, the loss is either minimal or undetectable by human observations. Lossy compression techniques are used for pictures and music files that can be trimmed at the edges. Unlike text files and processing files, pictures and music do not require reconstruction to be identical to the original, especially if the data dropped is insignificant or undetectable.

Image compression:

JPEG

Programs using complex graphics are showing up in virtually every area of computing applications including games, education, desktop publishing, graphical design, and most recently the World Wide Web. Although graphics do a great deal to enhance the usability and visual aesthetics of such applications, they consume prodigious amounts of disk storage.

When research into image compression began in the late 1970s, most compression concentrated on using conventional lossless techniques. However, such types of compression, which included statistical and dictionary methods of compression, did not tend to perform well on photographic, or continuous tone images. The primary problem with statistical techniques stemmed from the fact that pixels in photographic images tend to be well spread out over their entire range. If the colors in an image are plotted as a histogram based on frequency, the histogram is not as "spiky" as one would like for statistical compression to be effective. Each pixel code has approximately the same chance of appearing as any other, negating any opportunity for exploiting entropy differences (Nelson 349).

By the late 1980s, extensive research pushed the development of lossy compression algorithms that take advantage of known limitations of the human eye. Such algorithms play on the idea that slight modifications and loss of information during the compression/decompression process often do not affect the quality of the image as perceived by the human user. Eventually, the JPEG continuous tone image compression specification was standardized, named after the Joint Photographic Experts Group, the standards group consisting of members from both the CCITT and the ISO that wrote the specification. The JPEG specification includes separate lossy and lossless algorithms; however, the lossless algorithm is rarely used due to its poor compression ratios. Thus, when one mentions JPEG compression, it can almost be assumed that the reference is being made to the lossy algorithm, or the JPEG baseline algorithm. The baseline algorithm, which is capable of compressing continuous tone images to less that 10% of their original size without visible degradation of the image quality, is detailed below.

Audio compression:

MP3:

MP3 stands for MPEG-1 Layer 3. Layers represent a family of coding algorithms. Layer 1 has the lowest complexity compared to the other layers. Layer 2 requires a more complex encoder and decoder and is directed more towards different applications. Thus, Layer 2 is more able than Layer 1 to remove the redundancy in the signal that takes up space. Layer 3 is again more complex and further reduces redundancy and relevance from the data. . The layers are backwards-compatible, which means that any software or hardware capable of decoding Layer 3 audio should also be able to decode Layers 1 and 2.

So why has MP3 emerged as the leading tool for Internet audio delivery? MPEG-1 Layer 3 is defined as an open standard, so the specification is available to anyone interested in implementing the standard. Since no single company owns the standard, public example source code is available and the format is well defined. Also, driven by the demand for professional use, many MP3 encoders and decoders are readily available for use. This simplifies and accelerates the adoption of MP3 technology. Additionally, the widespread increase in usage of computers fast enough to decode audio, as well as increasingly fast and widely available Internet access, has contributed to the embracing of MP3 music format.

Video Compression:

Transmission of pictures has been possible for nearly a hundred years, starting with the first facsimile for news reporting just after the turn of the century. Television transmission started in the 1930s, delivering picture quality commensurate with available channel bandwidth. In the past fifteen years, picture quality has improved significantly with recording of the digitized video signal on tape and other media. As with analog video, the resulting quality of digital video is dependent on the information-carrying capacity of the channel. Today, the power of computers and some very clever mathematical algorithms have allowed digital-quality pictures to be delivered by a variety of communications methods with much lower channel data rate requirements. We call this combination of computers, television and communication technology "convergence."

By using video compression its possible to store pictures on computer disks at various quality levels depending on requirements for editing and other applications. Video transmission to the home with hundreds of programs is possible by cable or satellite. Traditional broadcast transmission will soon be providing high definition television or several standard definition digital television programs on the same channels that today provide only one analog program.

MPEG:

MPEG is a working group that was formed from the existing JPEG (Joint Photographic Experts Group) standard for bit reduction of still pictures. Its goal is to devise a suitable encoding scheme for transmitting moving pictures and sound over various broadcast links and recording them in standard digital storage media. Since moving pictures are often accompanied by sound, MPEG also defined a standard for encoding audio information. In 1992, a standard for audio and video encoding was devised known as MPEG-1.

Compression links:

http://www.arturocampos.com/cp_toc.html

http://www.stanford.edu/~udara/SOCO/

Viruses:

Preface:

If theres one word that can strike fear in the heart of any computer user, especially one who accesses the internet, or exchanges diskettes, that word is, "virus." Viruses can generate so much fear in the cyber world that news of a new virus often spreads faster than the virus itself. As the Information Manager of a company that produces software for the computer industry, I receive hundreds of diskettes per month and almost as many internet uploads from our customers. Consequently, I have come in contact with many viruses and I have learned quite a bit about them. Through my experiences I have learned that just as important as knowing what viruses can do, is knowing what they can not do.

What is a Virus?

First, what is a virus? A virus is simply a computer program that is intentionally written to attach itself to other programs or disk boot sectors and replicate whenever those programs are executed or those infected disks are accessed. Viruses, as purely replicating entities, will not harm your system as long as they are coded properly. Any system damage resulting from a purely replicating virus happens because of bugs in the code that conflict with the systems configuration. In other words, a well-written virus that only contains code to infect programs will not damage your system. Your programs will contain the virus, but no other harm is done. The real damage--the erasing of files, the formatting of hard drives, the scrambling of partition tables, etc.--is caused by intentional destructive code contained within the virus. Generally, the destructive part of a virus is programmed to execute when certain conditions are met, usually a certain date, day, time, or number of infections. An example is the now infamous Michelangelo virus. This virus can run rampant on your computer for months and you wont notice that anything is wrong. That is because even though your hard disks master boot record is infected with the virus, the destructive code has not yet been executed. The virus is programmed to trigger its destructive code on March 6, Michelangelos birthday. Therefore, if Michelangelo contained no destructive code, nothing bad would happen to your computer even though it was infected with a virus.

An important thing to remember is that not all virus attacks produce catastrophic results. For example, one of the most common viruses in the world is called Form. I got Form from a floppy disk given to me by a friend who didnt know he had the virus. In fact, I didnt know I had it either until I received a call from a company to whom I mailed my resume using that floppy disk. They called me, not to tell me that I got the job, of course, but rather that my computer had the Form virus. How embarrassing! Apparently, Form had been on my computer for a long time, but its effects were so slight that I never noticed it. The only peculiarity I encountered was a clicking sound that emitted from my PC speaker every time I pressed a key, but this only happened for one day. Later, I learned that Form is programmed to trigger this action on the 18th of every month. Other than that, it doesnt contain any destructive code.

 

How infection occurs:

Once the virus is active on the computer, it can copy itself to (infect) other files or disks as they are accessed by the user. Different types of viruses infect computers in particular ways; the most widespread types are Macro, Boot and Parasitic viruses.

Viral Conduits

There are several conduits for viruses. Any method through which a file can move from one user to another is a potential risk. The most prevalent of these conduits include the Internet, Email, and the sharing of removable media.

The Internet is the largest network of computers all capable of sharing resources and exchanging information. As information is shared, viruses may move from system to system. Any potential method which allows a file to be transferred may also allow a virus to be transferred.

Email is another conduit of viral transfer. Virus-infected email attachments may be sent from one email account to another infecting each user who receives and opens the email attachment.

Another simpler conduit for virus is through a removable media device such as a floppy disk or USB key. The device containing the infected file is moved to several machines infecting each system as it is used. Sometimes simply introducing the device into the system can activate specific viruses.

One potential way that viruses get into a computer is often overlooked. Hackers find weaknesses in operating systems that can be exploited by viruses or automated programs. Windows is rather susceptible to these attacks which is why Microsoft routinely distributes security updates and patches to hopefully plug these security leaks. An unpatched system can be infected by a malicious program  scanning the Internet searching for unprotected systems. One effective way to curb or eliminate these attacks is through the use of a properly configured firewall.

A firewall attempts to protect the internal system from external attack. Only authorized programs and processes are allowed to access resources on the protected system. Invading programs are denied entry and are prevented from harming the system.

Types of viruses:

Parasitic viruses (executable viruses): Parasitic viruses attach themselves to programs, also known as executables. When a user launches a program that has a parasitic virus, the virus is surreptitiously launched first. To cloak its presence from the user, the virus then triggers the original program to open. The parasitic virus, because the operating system understands it to be part of the program, is given the same rights as the program to which the virus is attached. These rights allow the virus to replicate, install itself into memory, or release its payload. In the absence of anti-virus software, only the payload might raise the normal users suspicions. A famous parasitic virus called Jerusalem has a payload of slowing down the system and eventually deleting every program the us er launches.

Macro viruses:A macro is an instruction that carries out program commands automatically. Many common applications (e.g. word processing, spreadsheet, and slide presentation applications) make use of macros. Macro viruses are macros that self-replicate. If a user accesses a document containing a viral macro and unwittingly executes this macro virus, it can then copy itself into that applications startup files. The computer is now infected--a copy of the macro virus resides on the machine.

Any document on that machine that uses the same application can then become infected. If the infected computer is on a network, the infection is likely to spread rapidly to other machines on the network. Moreover, if a copy of an infected file is passed to anyone else (for example, by email or floppy disk), the virus can spread to the recipients computer. This process of infection will end only when the virus is noticed and all viral macros are eradicated. Macro viruses are the most common type of viruses. Many popular modern applications allow macros. Macro viruses can be written with very little specialist knowledge, and these viruses can spread to any platform on which the application is running. However, the main reason for their success is that documents are exchanged far more frequently than executables or disks, a direct result of emails popularity and web use. Examples of macro viruses include W97M.Melissa , WM.NiceDay and W97M.Groov.

Boot sector viruses: The boot sector is the first software loaded onto your computer. This program resides on a disk, and this disk can be either the hard disk inside the computer, a floppy disk or a CD. When a computer is switched on, the hardware automatically locates and runs the boot sector program. This program then loads the rest of the operating system into memory. Without a boot sector, a computer cannot run software.

A boot sector virus infects computers by modifying the contents of the boot sector program. It replaces the legitimate contents with its own infected version. A boot sector virus can only infect a machine if it is used to boot-up your computer, e.g. if you start your computer by using a floppy disk with an infected boot sector, your computer is likely to be infected. A boot sector cannot infect a computer if it is introduced after the machine is running the operating system.

An example of a boot sector virus is Parity Boot. This viruss payload displays the message PARITY CHECK and freezes the operating system, rendering the computer useless. This virus message is taken from an actual error message which is displayed to users when a computers memory is faulty. As a result, a user whose computer is infected with the Parity Boot virus is led to believe that the machine has a memory fault rather than an disruptive virus infection.

Multi-partite viruses: Multi-partite (also known as polypartite) viruses infect both boot records and program files. These are particularly difficult to repair. If the boot area is cleaned, but the files are not, the boot area will be reinfected. The same true for cleaning infected files. If the virus is not removed from the boot area, any files that you have cleaned will be reinfected. Examples of multi-partite viruses include One_Half, Emperor, Anthrax and Tequilla.

Stealth virus: A stealth virus is one which hides the modifications it has made in the file or boot record, usually by taking over & monitoring the system functions used by programs to read files or physical blocks from storage media, and forging the results of such system functions so that programs which try to read these areas see the original uninfected form of the file instead of the actual infected form. Thus the virus modifications go undetected by anti-virus programs. Use of a clean floppy to boot will enable detection of a stealth virus. However, in order to do this, the virus must be resident in memory when the anti-virus program is executed.

Polymorphic code: Polymorphic code was the first technique that posed a serious threat to virus scanners. Just like regular encrypted viruses, a polymorphic virus infects files with an encrypted copy of itself, which is decoded by a decryption module. In the case of polymorphic viruses however, this decryption module is also modified on each infection. A well-written polymorphic virus therefore has no parts that stay the same on each infection, making it impossible to detect directly using signatures. Anti-virus software can detect it by decrypting the viruses using an emulator, or by statistical pattern analysis of the encrypted virus body. To enable polymorphic code, the virus has to have a polymorphic engine (also called mutating engine or mutation engine) somewhere in its encrypted body.

Some viruses employ polymorphic code in a way which constrains the mutation rate of the virus significantly. For example, a virus can be programmed to mutate only slightly over time, or it can be programmed to refrain from mutating when it infects a file on a computer that already contains copies of the virus. The advantage of using such slow polymorphic code is that it makes it more difficult for anti-virus professionals to obtain representative samples of the virus, because bait files that are infected in one run will typically contain identical or similar samples of the virus. This will make it more likely that the detection by the virus scanner will be unreliable, and that, as a result of this, some instances of the virus may be able to avoid detection.

Trojan horse: A Trojan Horse is not a Virus. It, however, is a program, often harmful, that pretends to be something else. For example, you might download what you think is a new game, but when you run it the files on your hard drive are deleted, or your passwords are e-mailed to another person. ( Note that the process of Downloading will NOT infect your system. It is only when the downloaded program is executed (run) that the computer becomes infected. N.B. the importance of scanning the downloaded program before opening or running it.) Trojan Horses are impostors--files that claim to be something desirable but, in fact, are malicious. A very important distinction from true viruses is that they do not replicate themselves, as viruses do. Trojans contain malicious code, that, when triggered, cause loss, or even theft, of data. In order for a Trojan Horse to spread, you must, in effect, invite these programs onto your computers--for example, by opening an email attachment. The PWSteal.Trojan is a Trojan.

 

Worm:

• Worms are programs that replicate themselves from system to system (machine to machine) without the use of a host file.
• Worms usually move around and infect other machines through computer networks. This is in contrast to viruses, which requires the spreading of an infected host file.
• Worms use up computer time and network banadwidth when they are replicating, slowing down internet traffic.
• Usually the worm will release a document that already has the "worm" macro inside the document. As an example the Code Red worm was designed to replicate itself for the first 20 days of the month, replace web pages on infected servers with a page that declares "hacked by chinese" and finally at a specific time and date, launch a concerted attack on the White House Web server in an attempt to overwhelm it.

Hoax:

Hoaxes are arguably nothing more than a manually-driven email worm. By definition, a worm is a piece of malicious code that copies itself over and over again, either on the users system or, in modern times, by spreading itself through email. While the real worm relies on coding to achieve spread, the craftily worded hoax simply relies on the user to do its dirty deed. As a result, a hoax can spread around the Internet in hours, clogging inboxes, saturating mail servers, and frustrating administrators who are charged with debunking these erroneous messages. The fact is, hoaxes have only one purpose in life and that is to spread to as many people as possible. Quite the same goal as most viruses, in fact.

Some of the common phrases used in these hoaxes are:
- If you receive an email titled [email virus hoax name here], do not open it!
- Delete it immediately!
- It contains the [hoax name] virus.
- It will delete everything on your hard drive and [extreme and improbable danger specified here].
- This virus was announced today by [reputable organization name here].
- Forward this warning to everyone you know!

Most virus hoax warnings do not deviate far from the pattern described above and Warnings about viruses that will physically destroy your computer are usually hoaxes, not legitimate virus warnings.

Symptoms of Virus infections:

• Change in File size.
• Unusual messages or displays on the monitor
• unusual sounds or music played at random times
• less available memory than you should have
• a disc or volume name has been changed
• programs or files are suddenly missing
• unknown programs or files have been created
• Some files are currupted or suddenly wont work properly
• system slowdown

Lines of Defense:

Prevention: The best way for users to protect themselves against viruses is to apply the following anti-virus measures:

* Make backups of all software (including operating systems), so if a virus attack has been made, you can retrieve safe copies of your files and software. * Inform all users that the risk of infection grows exponentially when people exchange floppy disks, download web material or open email attachments without caution. * Have anti-virus (AV) software installed and updated regularly to detect, report and (where appropriate) disinfect viruses. * If in doubt about a suspicious item that your anti-virus software does not recognise, contact a Computer Proffessional for analysis.

Antivirus programs

Special programs have been created to deal with the problem of viruses. Antivirus programs attempt to detect viruses and then rid the infected system of them. The antivirus programs have two major components – the engine and the definition files. The antivirus engine is the actual program that hunts for and destroys the virus programs. It is a relatively stable piece of software and does not change very often. The second component, the definition files, contains the specific markers that identify particular viruses. Since each virus typically has it own individual marker, one set of definition files will not apply to every virus. The definition files must be updated frequently so that the engine will be able to identify new viruses and deal with new threats.

An antivirus program usually cannot handle a new threat; the updated virus definitions inform the engine how to proceed. If a new virus infects a system before applicable updated definition files are available, the virus may go unchecked running rampant on the system and infecting other systems. This is often the case when a brand new virus is created. Once an updated definition is created and made available to the public, the virus can then be correctly identified, controls, and eliminated. Most antivirus vendors sell an antivirus system that contains both the engine and the most current definitions. The vendors’ websites often keep updated definition files that can be downloaded and used to strengthen the virus protection on the system.

Common programmes:

• AntiVir Personal Edition - FREE virus scanner and cleaner
• Avast32 AntiVirus - FREE virus scanner and recovery
• AVG AntiVirus - FREE - Scans and repairs
• BitDefender AntiVirus Home Edition - Scans, repairs, and include Live! Updates
• Command AntiVirus - Scans and repairs
• eTrust EZ AntivirusScans and repairs
• F-Prot Antivirus for Windows, DOS, Linux, FreeBSD Scan and repair (Frisk Software)
• McAfee FREE Scan - FREE Scanner with additional information provided if viruses are found
• McAfee VirusScan Online - VirusScan Online protects and repairs PC from viruses, worms and trojans (automatic updates)
• McAfee VirusScan Home Edition - Comprehensive antivirus protection
• Nod32 AntiVirus - Protection and cleaner against viruses, worms, and other malware
• Norman Virus Control - Scans and repairs - comprehensive protection
• Panda Antivirus - Detects and eliminates all types of viruses & includes an automatic update feature
• Rav AntiVirus Desktop for Windows and Linux - Highly effective antivirus program designed to protect servers and workstations
• Symantec - Norton AntiVirus Scan and repair (select Norton AntiVirus from dropdown list)
• Trend Micro Pc-cillin - Virus Protection and Internet Security (firewall) for Home Users
• VCatch - Virus protection - FREE tool that will check all the files sent or downloaded to your computer via Email and Web applications. Scanner and notification only.

 

 

Links:

http://www.hicom.net/~oedipus/virus32.html

http://www.ulm.edu/~hutton/instructionaltech/resources/faq/virus.html

http://en.wikipedia.org/wiki/Computer_virus

PC Suli II. page:125.-151.

Overview

Whats compression? A method of making files smaller on disk.

Lossless Compression: Lossless compression techniques, as their name implies, involve no loss of information. If data have been losslessly compressed, the original data can be recovered exactly from the compressed data after a compress/expand cycle. Lossless compression is generally used for so-called "discrete" data, such as database records, spreadsheets, word-processing files, and even some kinds of image and video information.In essence, lossless compression algorithms are needed in cases that require compression where we want the reconstruction to be identical to the original.

Lossy Compression: Lossy compression, as its name implies—some amount of data may be lost in the process.  Thus, after a compression/decompression cycle, the data set will be modified from the uncompressed original and information may be lost. Lossy compression techniques attempt to eliminate unnecessary or redundant information, focusing more on saving space over preserving the accuracy of the data. Ideally, the loss is either minimal or undetectable by human observations. Lossy compression techniques are used for pictures and music files that can be trimmed at the edges, especially if the data dropped is insignificant or undetectable.

What is a virus? A computer virus is a small program written to alter the way a computer operates, without the permission or knowledge of the user. It is a self-replicating program that spreads by inserting copies of itself into other executable code or documents.

 

Virus infection: When a virus infects the files, copies itself into it.

Virus activation: When the virus run itself, and begun take it’s effect on the computer and duplicates itself. It’s usually done without user permission, or it happens when you run the infected file.

Types of Viruses: There are several main types of virus infections.

• The "boot-sector infector" type usually resides on a floppy disk or hard drive. As the disks are moved from computer to computer, the boot sector looks for other boot sectors to inhabit. Each time the system boots, the virus activates reinfecting files and other drives.
• The "email virus" is one that attacks email programs and seizes the computer’s address book. The infected computer then emails copies of itself to the people found in the address book.
• The "macro virus" is a virus that inhabits MS Word documents. In most cases, the macro virus does damage to the document where it lives.
• The "executable virus" is a program that must be run to do damage. Often found in email attachments, this virus frequently is named with a cute title to fool users into activating it. Once activated, the virus can then do its damage.

 

Antivirus programs: Antivirus programs attempt to detect viruses and then rid the infected system of them.

Common antivirus programmes are:

NortonAntivirus          Kaspersky Antivirus                McAfee Antivirus

 

---- 15. Tétel ----

 

 

.: The creation of the Internet

 

The cores forming the Internet started out in 1969 as the ARPANET, created by the United States Department of Defense Advanced Research Projects Agency (ARPA). Some early research which contributed to the ARPANET included work on decentralised networks, queueing theory, and packet switching. On January 1, 1983, the ARPANET changed its core networking protocols from NCP to TCP/IP, marking the start of the Internet as we know it today.

 

Another important step in the development was National Science Foundations (NSF) building of a university backbone, the NSFNet, in 1986. Important disparate networks that have successfully been accommodated within the Internet include Usenet and Bitnet.

 

The collective network gained a public face in the 1990s. In 1991 and 1993 the term World Wide Web came to the scene and the creation of HTML and HTTP began. A few academic and government institutions contributed pages but the public didnt begin to see them yet. In 1993 the Mosaic web browser version 1.0 was released, and by late 1994 there was growing public interest in the previously academic/technical internet. By 1996 the word "Internet" was common public currency, but it referred almost entirely to the World Wide Web.

 

Meanwhile, over the course of the decade, the Internet successfully accommodated the majority of previously existing computer networks (some networks such as Fidonet have remained separate). This growth is often attributed to the lack of central administration, which allows organic growth of the network, as well as the non-proprietary nature of the Internet protocols, which encourages vendor interoperability and prevents one company from exerting control over the network.

 

.: TCP/IP

 

The Internet protocol suite is the set of communications protocols that implement the protocol stack on which the Internet runs. It is sometimes called the TCP/IP protocol suite, after the two most important protocols in it: the Transmission Control Protocol (TCP) and the Internet Protocol (IP), which were also the first two defined.

 

An IP address is a unique number, akin to a telephone number, used by machines (usually computers) to refer to each other when sending information through the Internet using the Internet Protocol. This allows machines passing the information onwards on behalf of the sender to know where to send it next, and for the machine receiving the information to know that it is the intended destination.

 

The Internet Protocol (IP) knows each logical host interface by a number, the so-called IP address. On any given network, this number must be unique among all the host interfaces that communicate through this network. Users of the Internet are sometimes given a host name in addition to their numerical IP address by their ISP.

 

The IP addresses of users browsing the world wide web are used to enable communications with the server of the web site. Also, it is usually in the header of email messages one sends. In fact, for all programs that utilize the TCP/IP protocol, the sender IP address and destination IP address are required in order to establish communications and send data.

 

Depending on ones Internet connection the IP address can be the same every time one connects (called a static IP address), or different every time on connects, (called a dynamic IP address). In order to use a dynamic IP address, there must exist a server which can provide the address. IP addresses are usually given out through a service called DHCP or the Dynamic Host Configuration Protocol.

 

Internet addresses are needed not only for unique enumeration of hosted interfaces, but also for routing purposes, therefore a high fraction of them are always unused or reserved.

 

 

 

.: Services of the Internet

 

-web

 

One of the most common services of the Internet is browsing webpages via HTTP (Hyper Text Transfer Protocol). The original purpose was to provide a way to publish and receive HTML pages. In other words thou can download pages containing data in html language.

 

 

-ftp

 

One of the most useful services of the Internet is FTP, or File Transfer Protocol. FTP is a network protocol. It also refers to the method by which we transfer data and program files between computers on the Internet. We refer to computers configured to accept FTP requests as FTP servers. These servers store a tremendous amount of information, and it is available to anyone on the Internet using FTP. In an FTP client/server connection, the users computer is called the client or local computer. The FTP server is called the host or remote computer. Downloading refers to transferring files from the FTP server to the client computer. Uploading refers to transferring files to the FTP server from the client computer.

 

-chat

 

A method people can real-time communicate via the net using clients to join specified servers. Poeple joining a server can usually chat w/ other ppl on the same server or network.

 

-telnet

 

Telnet is a network protocol used on the Internet or local area network (LAN) connections.

It is typically used to provide user oriented command line login sessions between hosts on the Internet.

By extension, telnet is ; the telnet program provides the client part of the protocol. Telnet clients have been available on most Unix systems for many years, and are available for virtually all types of computers.

 

.: Connecting to the Internet

 

The method of connecting to the internet starts at the client computer. The computer starts a connecting session via the modem (a device to encode and transfer data from the internet to the users computer) to build up a line between the client and the server what it belongs to. It is mostly the internet service providers core router what directly connects to the Regional Backbone Network. There are several RBN-s which creates the internet as it is.

 



15. Introduce an e-mail software

Microsoft Office Outlook 2003

In general

What is the e-mail?

Short for electronic mail, the transmission of messages over communications networks. The messages can be notes entered from the keyboard or electronic files stored on disk. Most mainframes, minicomputers, and computer networks have an e-mail system. Some electronic-mail systems are confined to a single computer system or network, but others have gateways to other computer systems, enabling users to send electronic mail anywhere in the world. Companies that are fully computerized make extensive use of e-mail because it is fast, flexible, and reliable.

Most e-mail systems include a rudimentary text editor for composing messages, but many allow you to edit your messages using any editor you want. You then send the message to the recipient by specifying the recipients address. You can also send the same message to several users at once. This is called broadcasting.

Sent messages are stored in electronic mailboxes until the recipient fetches them. To see if you have any mail, you may have to check your electronic mailbox periodically, although many systems alert you when mail is received. After reading your mail, you can store it in a text file, forward it to other users, or delete it. Copies of memos can be printed out on a printer if you want a paper copy.

All online services and Internet Service Providers (ISPs) offer e-mail, and most also support gateways so that you can exchange mail with users of other systems. Usually, it takes only a few seconds or minutes for mail to arrive at its destination. This is a particularly effective way to communicate with a group because you can broadcast a message or document to everyone in the group at once.

Although different e-mail systems use different formats, there are some emerging standards that are making it possible for users on all systems to exchange messages. In the PC world, an important e-mail standard is MAPI. The CCITT standards organization has developed the X.400 standard, which attempts to provide a universal way of addressing messages. To date, though, the de facto addressing standard is the one used by the Internet system because almost all e-mail systems have an Internet gateway.

E-mail address components

Internet e-mail addresses typically have two main parts:

professor@learnthenet.com

First there is the user name (professor) that refers to the recipients mailbox. Then theres an at sign (@). Next comes the host name (learnthenet), also called the domain name. This refers to the mail server, the computer where the recipient has an electronic mailbox. Its usually the name of a company or organization.

The end of the domain name consists of a dot (".") followed by three or more letters (such as .com and .gov) that indicate the top-level domain (TLD). This part of the domain name indicates the type of organization or the country where the host server is located.

How to use Outlook

I. Messaging

With Outlook, communicating by e-mail is quick and easy. You can send messages to people in your office and at other locations regardless of what e-mail software your message recipient is using.

Addressing and Sending a New E-Mail Message

When you address e-mail messages, you can specify different ways of sending the message: directly, as a courtesy copy, or as a blind courtesy copy. In each case, the same message is sent to each recipient. The names of Bcc (blind courtesy copy) message recipients are not visible in the message header; therefore, other message recipients are not aware of them. Message replies are not sent to Bcc recipients of the original message. If you are working on a network that uses Microsoft Exchange Server, when you send messages to other people on your network, you can type just the part of the address that is to the left of the @ sign. The remaining part of the address identifies the server that handles the e-mail account, so within an organization, the server name is not needed.

Handling E-Mail Messages You Receive

You can reply to e-mail messages in different ways: You can reply only to the person who sent the message, or you can reply to the person who sent the message and all the people to whom the original message was addressed. Whether you reply to only the sender or to everyone, your reply does not include any files that were attached to the original message. You can forward a message you have received to any other e-mail user (not only Outlook users). When you forward a message, the message recipient receives the text of the message as well as any files that were attached to the original message.

Sending and Replying to Instant Messages

You can communicate with your contacts in real time with instant messages. Instant messaging (IM) is a private online chat method. After you establish a connection with someone who is online and using instant messaging, messages you send to that person appear on his or her screen instantly. Likewise, you see responses from that person instantly on your screen. Instant messaging is especially useful for brief exchanges and can be much more immediate than e-mail. By default, Outlook supports instant messaging using Microsoft Windows Messenger, Microsoft MSN Messenger, and Microsoft Exchange Instant Messaging Service. When Outlook starts, you are automatically logged on to the service you installed. Before you can use instant messaging, you must obtain the instant messaging addresses of the people you want to communicate with, and add those addresses to the Outlook Contact forms of those people. Then they have to tell their instant messaging programs to accept messages from your address.

After this setup work is done, when you log on to your instant messaging service, you can see whether a contact is online. A contact’s online status is displayed in the InfoBar on the Contact form and on any e-mail address associated with the contact. You can specify how your online status appears to others. For example, if you need to step away from your desk, you can set your status to Be Right Back so that any contacts who are online can see that you are temporarily unavailable.

Attach Files to Items

When sending e-mail and instant messages to other people, you can include electronic files (such as documents, spreadsheets, graphics, or text files) along with your message. This can be a quick and efficient way of distributing information to other people. When sending file attachments, be sure that your recipients have the software required to open your file. For example, if you are attaching a Word document, your recipients must have Word installed on their computers to open your attachment.

Attaching a File to an E-Mail Message

You can attach any type of file to an e-mail message, but Outlook prevents users from receiving certain types of files that could constitute a security hazard. The maximum attachment size that your contacts can receive will vary depending on their e-mail systems. The time required to download an e-mail attachment varies depending on the recipient’s Internet connection speed.

Sending a File Through an Instant Message

You can send files to contacts during instant messaging sessions. The files are not actually attached to the message; instead, a link to the file is embedded in the message. Your IM contact can click the link to download the file to his or her computer.

Create and Modify a Personal Signature for Messages

You can use an e-mail signature to personalize your messages and save time. A signature is a predefined block of text that can be inserted, manually or automatically, at the end of your outgoing messages.

Creating and Modifying an E-Mail Signature

Signatures can include any text you like, but they typically include your name, title, and company name. Signatures can be formatted in the same ways that message text can be formatted.

Specifying Unique Signatures for Multiple E-Mail Accounts

You can create multiple signatures for different uses, such as formal business e-mail, casual business e-mail, and personal e-mail. If you use Outlook to access more than one e-mail account (for instance, your work and personal accounts) you can instruct Outlook to attach a specific, unique signature to each account.

Modify E-Mail Message Settings and Delivery Options

You can’t always answer every message as soon as you read it, but you can mark messages that require response or action by attaching a follow-up flag. Outlook 2003 features Quick Flags, an easy way to flag messages.

You can send e-mail messages from Outlook in different formats, each designed to fit different needs. To help you manage your e-mail and convey the meaning of your messages more effectively, you can set the importance, sensitivity, and a number of delivery options for e-mail messages.

Flagging an E-Mail Message for Follow-Up

Flags come in six colors; you can use the different colors to indicate different types of follow up, and you can set a reminder to pop up when the follow-up is due. You can quickly view your flagged messages by using the For Follow-up Search folder.

Each message in your Inbox has a shaded Flag Status icon that indicates whether a message is flagged or completed. You can flag messages in any folder, but the Flag Status icon appears only in active Inbox folders.

Setting E-Mail Message Formats

E-mail messages are sent in one of three formats: HTML, Plain Text, or Outlook Rich Text Format (RTF). Outlook supports all three formats. Other e-mail programs might be able to work with only some of them.

■ HTML is the default Outlook message format. HTML supports text formatting, numbering, bullets, pictures and backgrounds in the message body, styles, and stationery. Most popular e-mail programs support HTML messages.

■ Outlook Rich Text Format supports a host of formatting options including text formatting, bullets, numbering, background colors, borders, and shading.

■ Plain Text is supported by all e-mail programs, but as the name implies, messages in Plain Text do not include any formatting.

For the most part, the HTML message format will meet your needs. When you send an HTML message to someone whose e-mail program doesn’t support HTML format, the message is displayed as Plain Text in the recipient’s e-mail program. Outlook automatically converts RTF messages you send over the Internet into HTML format. When you reply to or forward a message, Outlook uses the format of the original message by default. However, you can choose the format for any message you send.

When sending messages in HTML format, you can enhance the appearance of your messages by using stationery and themes. When you use stationery, you can specify the background, fonts, bullets, images, and other elements you want to use in outgoing e-mail messages. You can choose from a collection of predefined stationery that comes with Outlook, customize one of the patterns, create new stationery, or download new patterns from the Web. If you use Microsoft Office Word as your e-mail editor, you can choose from additional patterns available as Word themes.

Setting E-Mail Message Importance, Sensitivity, and Delivery Options

You can set a message to High, Normal, or Low importance. Messages sent with High importance are indicated by a red exclamation point. Messages that were sent with Normal importance have no special indicator. Messages that were sent with Low importance are indicated by a blue downward-pointing arrow. These indicators appear in the Importance column in the Inbox.

You can also set message sensitivity to Normal, Personal, Private, or Confidential. Messages marked as Private cannot be modified after they are sent.

To help you manage messages you receive, you can choose to have replies to your messages sent to another e-mail address. For example, you might have replies sent to a new e-mail address as you transition from one to another. To help you manage messages you send, you can choose whether to save copies of your sent messages and in which folder they should be saved. You can also specify when a message will be delivered, and expire messages after a certain date and time. When a message expires, the sender and receipt information are “crossed out” in the recipient’s Inbox to indicate that he or she does not need to read the message.

Create and Edit Contacts

Think of your Outlook Contacts list as a powerful electronic Rolodex, where you can store all the information you need to stay in touch with contacts. For each contact entry, you can store the following types of information:

■ Name, job title, and company name

■ Business, home, and other addresses

■ Business, home, fax, mobile, pager, and other phone numbers

■ E-mail, Web page, and instant messaging addresses

You can also store the following details for each contact entry:

■ Professional information, including department, office, profession, manager’s name and assistant’s name

■ Personal information, including nickname, spouse’s name, birthday, anniversary, and the title and suffix to use in correspondence

■ The directory server and e-mail alias to use for online meetings

■ The address of the contact’s free/busy information server

Creating and Updating Contact Entries

You can create an entry for a contact with as little as a name, or as much information as you want. You can add general notes and track all the Outlook activities that are connected with each contact. You can add to or change the information for a contact at any time. To save time, you can create contact entries for people who work for the same company based on an existing contact from that company.

If you have Person Names smart tags enabled, you can add contact entries to your Outlook Contacts list from an e-mail message form or from the Reading Pane.

Creating Instant Messaging Contact Entries

If you use Windows Messenger or MSN Messenger, you can create contact entries directly in your instant messaging program, or add them from your Outlook Contacts list to your Messenger contact list.

Accept, Decline, and Delegate Tasks

When another Outlook user assigns a task to you through Outlook, you become the temporary task owner. You then have three options:

■ You can accept the task. When you accept a task, it is added to your Outlook Tasks list. If the original task owner requested it, a copy of the task is kept in his or her Tasks list so he or she can see your progress.

■ You can decline the task. If you do so, the task is returned to the original task owner, who can reclaim or reassign the task.

■ You can delegate the task to another person. If that person accepts the task, he or he becomes the task owner. If not, the task is returned to you.

Handling Task Assignments

When you receive a task request, you must accept or decline the task in the same way that you would accept or decline a meeting.

II. Scheduling

Create and Modify Appointments, Meetings, and Events

Adding your time commitments to a calendar can help you manage your daily schedule. You can use Outlook’s Calendar to schedule appointments (which typically last just part of a day) or events (which typically last all day). For example, you might create an appointment in your Outlook Calendar for the time you will spend seeing your doctor, and you might schedule an event for an all-day seminar you plan to attend. You can also schedule meetings and meeting resources. When you schedule a meeting, you send an invitation to each attendee. If your meeting attendees use Outlook, the meeting is placed in their Calendars unless declined.

Adding an Appointment or Event to the Outlook Calendar

Both appointments and events can be recurring, meaning they occur repeatedly at regular intervals—for example, daily, weekly, or monthly. You can specify a subject and location for each Calendar item as well as the date and time. You can indicate your availability as available, tentative, busy, or out of the office during the scheduled time, and you can choose to receive a reminder of an appointment or event. Reminders are displayed in a small dialog box that appears as the time of the appointment or event approaches. Outlook must be open for you to receive reminders.

Inviting People and Resources to a Meeting

You can use Outlook to schedule meetings and invite attendees—both those who work for our organization and those who don’t. To choose a date and time for your meeting, you can check the availability of attendees and resources by viewing their free/busy information. When inviting attendees from within your organization, you can automatically see their Outlook Calendar information. You can see free/busy information for people outside of your organization only if they make this information available over the Internet.

You can choose the meeting time, or to have Outlook select it for you, you can provide a list of attendees and indicate whether the attendance of each invitee is required or optional. Outlook uses this information to search for available meeting times, prioritizing times that work for all required attendees and most optional attendees. After you have selected a time, you send a meeting request—a type of e-mail message—to each invited attendee and requested resource. Responses from attendees and those responsible for scheduling the resources you requested are tracked as you receive them.

If you are working on a network that uses Microsoft Exchange Server and your system administrator includes resources (such as conference rooms, audiovisual equipment, or meeting supplies) in the organization’s Global Address List, you can reserve those resources by inviting them to the meeting. Your meeting request is sent to the person who manages the schedule for the resource. That person responds to your meeting request based on the availability of the resource.

Update, Cancel, and Respond to Meeting Requests

Scheduling a meeting sends a meeting request e-mail message to each attendee and places the meeting on each attendee’s Outlook Calendar, as well as on your own. Meeting requests give the attendee the option to accept or decline the meeting, or propose a new meeting time. The number of attendees who have accepted or declined your meeting request is visible in the meeting form on your Calendar.

As the meeting organizer, you can update a meeting or cancel it at any time from your Calendar.

Responding to a Meeting Request

Just as you can send meeting requests, other people can send them to you. When you receive a meeting request, you can respond in one of four ways:

■ You can accept the request and inform the meeting organizer that you will attend. Meetings that you accept are entered in your Calendar.

■ You can tentatively accept a request, indicating that you might be able to attend the meeting. Meetings that you accept tentatively are also entered in your Calendar, but your free/busy information will show you as only tentatively scheduled for that time.

■ You can propose a new meeting time, in which case the request is referred to the meeting organizer for confirmation. Your Calendar shows the proposed new meeting time as tentatively scheduled.

■ You can decline a meeting, in which case the request is deleted and no entry is made in your Calendar. When you decline a meeting, you can choose whether Outlook notifies the person who sent the request.

If you prefer, you can choose to respond to meeting requests automatically. Outlook will process meeting requests and cancellations as you receive them, responding to requests, adding new meetings to your Calendar, and removing cancelled meetings. If you choose, Outlook will automatically decline meeting requests that conflict with existing items on your Calendar. You can also choose to automatically decline any request for a recurring meeting.

Updating or Canceling a Meeting

People’s schedules can shift on a daily basis. Outlook makes it easy to update or cancel meetings as your needs change. For example, an important attendee might be sick or delayed, or have other plans come up that take precedence over your meeting. In this case, you can change the date or time of the meeting or cancel the meeting altogether. You can also add people to or remove people from the list of attendees.

Customize Calendar Settings

The Outlook Calendar is a versatile tool. You can quickly display traditional calendar pages for a variety of time periods. You can also display the calendar items in list format, grouped by type or category.

Using the Work Week option, you can specify the time periods during which you are generally available for work-related events. This helps people who are scheduling meetings with you to make them at a suitable time.

Setting Your Outlook Calendar Options

To help you stay on top of your schedule, you can view your Calendar for a variety of time periods:

■ Day view displays one day at a time, separated into half-hour increments.

■ Work Week view displays your defined work week in columnar format.

■ Week view displays one calendar week at a time.

■ Month view displays five weeks at a time. This is the default Calendar view. To help you find the Calendar items you are looking for, Outlook offers a number of Calendar view modes:

■ Day/Week/Month displays a calendar-like view of appointments, events, and meetings for the period of time you specify. This is the default view, and it includes the Date Navigator.

■ Day/Week/Month With AutoPreview is the Day/Week/Month view with the addition of the first line of comment text for each Calendar item.

■ Active Appointments displays a list of appointments and meetings scheduled for today and in the future, showing details in columns.

■ Events displays a list of events, showing details in columns.

■ Annual Events displays a list of annual events, showing details in columns.

■ Recurring Appointments displays a list of recurring appointments, showing details in columns.

■ By Category displays a list of all items, grouped by category, showing details in columns.

Defining Your Available Time

You can tell Outlook what your work schedule is so that other people can make appointments with you only during the times when you plan to be available. This defined time is called your work week. The work week is colored differently on your Calendar, and by default is the only time displayed to other people on your network who look at your Calendar. By default, Outlook defines the work week as Monday through Friday from 8:00 A.M. to 5:00 P.M. You can change this to suit your needs—for instance, if you work a late shift or weekends.

Create, Modify, and Assign Tasks

You can create and store a list of tasks for any activity that you want to remember and track to completion. The tasks can be your own, or you can delegate them to other people.

Creating and Modifying a Task

For each task, you can specify a due date and a start date. A task is displayed in your Tasks list beginning on the start date. A task that is incomplete past its due date is displayed in red to indicate that it is overdue. You can also set the priority of a task—High for urgent tasks, and Normal and Low for less important tasks. And you can choose to set a reminder for a task, much like reminders for appointments. Tasks can recur either at regular intervals or at intervals based on the date on which you mark the task complete. For example, you might create a task to review the status of a project every seven days. If you perform your review on a Friday and mark the task as complete, Outlook creates the next instance of the task as due on the following Friday. If you perform your next review on a Thursday, Outlook creates the next instance of the task as due on the following Thursday. A task that you create to recur at a regular interval will be regenerated at that interval regardless of the status of earlier instances of the task. For example, you might create a task for submitting your employees’ expense reports to the finance department on the fifth of each month. When you mark the task as complete, regardless of the day, Outlook creates the next instance of the task and marks it as due on the fifth of the next month. As you complete your tasks, you will want to remove them from your to-do list. You might find that some tasks are unnecessary and can be deleted. You might also acquire new tasks that other Outlook users assign to you, asking that you report back on your progress. Outlook makes it easy to manage changes to your tasks. You can create and modify tasks in the Tasks folder or in the TaskPad that appears in the default Calendar view.

Assigning a Task

You can create a task in Outlook and assign it to someone else for completion. You might delegate a task to your assistant, or when your project depends on receiving something from another department, you might assign a task to your contact in that department.

Although you can update the tasks you create for yourself, when you assign a task to someone else, only that person can update it. However, you can keep a copy of the task in your Tasks list, and your copy will be updated as the other person updates the tasks. For example, if the other person changes the status or the percent complete, your copy of the task will be updated. You can also specify that you want to receive status reports for the task. Status reports are special e-mail messages that reflect the current status of a task.

III. Organizing

Create and Modify Distribution Lists

Address book entries can be for an individual contact or for a distribution list—a group of individual addresses stored as a single entity. For example, to facilitate communication within a team, you might create a distribution list including the addresses for all the people working on a particular project.

Creating a Distribution List

You can create a distribution list from existing contact entries, or you can add contact information directly to the distribution list. In this way, you can maintain a distribution list of people to whom you wouldn’t necessarily send e-mail messages on a regular basis, thus keeping your Contacts folder smaller and easier to manage.

Modifying a Distribution List

You can add members to an existing distribution list, delete members from a distribution list, or change distribution list member contact information at any time by opening the distribution list form. You can also remove distribution list member from specific e-mail messages—for example, if a person is on vacation and you don’t want to clutter up his or her Inbox, or if you want to let the rest of the group know about an event (such as a surprise birthday party).

Link Contacts to Other Items

Keeping track of what’s been done or needs to be done in connection with a particular contact can be challenging. You can link contact entries to other Outlook items including appointments or events, journal entries, notes, and e-mail messages.

Linking an Outlook Item to a Contact Entry

You can use Outlook Notes to record information about your dealings with contacts. For example, after a phone call with a client, you might link a note you created during that call to the contact information for that client. You can also forward that note to a co-worker who is working with the same client.

Create and Modify Notes

You can use Outlook’s Notes feature to record questions, ideas, reminders, messages, or anything else that you might otherwise write down. Because you can leave notes open on your screen even while Outlook is minimized, they are especially useful for storing small bits of information that you might need as you work. For example, you might open a Note form to record your notes during a phone conference, or you might use a note to jot down useful references you find while doing research on the Web.

Creating and Editing Notes

You can create notes from scratch or by dragging information to the Notes icon in the Navigation Pane.

Organize Items

If you use Outlook on a regular basis, it won’t take long for you to accumulate a variety of information. Outlook includes a number of methods for personalizing the way you view and sort information so that you can more easily find what you’re looking for. You can change the information that is displayed in individual folders, change the way it is displayed, and manually or automatically sort and label items.

Adding and Deleting Fields from Folder Views

You can collect a large amount of information in an Outlook item. Not all the information is displayed by default in every folder view. You can customize the information shown by adding or removing fields from the folder view.

Sorting Outlook Items

Regardless of the view you choose, you can group and sort your Outlook items by any column simply by clicking the column heading. By default, messages in your Inbox are grouped by the received date in descending order—the most recent messages appear at the top of the list. Messages you received this week are grouped by day. Earlier messages are grouped by weeks or longer periods. You can sort columns in either ascending or descending order. You can also group your messages by the contents of any column—by the sender of the message, for instance, or by the subject.

A downward-pointing arrow in a column header indicates that the folder items are sorted in descending order by that column. An upward-pointing arrow indicates that items are sorted in ascending order.

When items are grouped, the total number of items and the number of unread items in each group is indicated in parentheses following the conversation subject.

Filtering E-Mail Messages

As messages accumulate in your Inbox, it can be a challenge to find specific messages or groups of messages. To make locating individual messages easier, you can filter your messages to display only those messages that meet common criteria, helping you identify a specific collection of messages.

Organizing Outlook Items by Using Colors

There are many ways to use color to organize your Outlook items:

■ You can display e-mail message header information in any of the 16 system colors to help you easily distinguish messages with certain characteristics. For example, you might show all messages from your boss in red, and all messages from the finance department in green. You can also choose to have messages that were sent only to you displayed in a different color than messages sent to multiple recipients.

■ You can color-code appointments, meetings, and events, choosing from one of ten colors. Each color is identified with a preset label: None, Important, Business, Personal, Vacation, Must Attend, Travel Required, Needs Preparation, Birthday, Anniversary, and Phone Call. If the default labels don’t fit your needs, you can edit them to suit.

■ You can change the color of notes from the default yellow to white, pink, green, or blue. There are no default meanings associated with the colors, but you can create your own system; for example, coloring business-related notes yellow, finance-related notes green, and personal notes pink.

Organizing E-Mail Messages by Using Rules

You can instruct Outlook to evaluate your e-mail messages in the same way that you would evaluate them, and to make corresponding decisions about what to do with them. These instructions are called rules. You can create rules that process messages as they arrive or as you send them; checking for names, words, attachments, categories, or other message conditions on which you might base processing decisions. After the messages are evaluated, Outlook can automatically move, copy, delete, forward, redirect, reply to, or otherwise process messages that meet the criteria you set.

Rules that are applied to messages as they are received or processed by the Exchange server are called server rules. Rules that are applied to messages on your computer are called client rules.

Organizing Outlook Items by Using Views

You can choose different ways of displaying the items stored in each Outlook folder to make the information contained therein most accessible to you. If you change views frequently, you can display a list of available views in the Navigation Pane so you can quickly switch between them.

Organize Items Using Folders

Creating folders to organize your messages helps you avoid an accumulation of unrelated messages in your Inbox. For example, you can create a folder for each project you’re working on and store all messages regarding a particular project in its own folder.

Organizing E-Mail Messages in Folders

After you create the folder structure in which you want to organize your messages, you can move messages to the folders manually or have Outlook move them for you.

Archiving Outlook Items

As messages accumulate in your Inbox and other message folders, you might need to consider other ways to store them to reduce the storage space you’re using. For example, you might want to archive all messages sent or received before a certain date. Archiving messages in a separate Outlook message file helps reduce clutter and the size of your primary message file, while still allowing easy access to archived messages from within Outlook. You can archive messages manually or automatically. When archived messages are moved to a separate message file, the messages are removed from their original folder. By default, Outlook automatically archives messages in all folders at regular intervals to a location determined by your operating system. You can change the default global settings for the AutoArchive function and specify varying archive settings for specific folders. Archive settings selected for a specific folder override the global settings for that folder. If you don’t specify AutoArchive settings for a folder, Outlook uses the global settings.

Search for Items

If you don’t know the particulars of a message that you’re looking for, such as the sender, subject, or date received, or if you don’t know what folder the message is stored in, it can be difficult to find a specific message by sorting. When you don’t know precisely what you’re looking for, Outlook’s Find feature helps you search with a minimum amount of information. If you frequently need to find messages that share certain characteristics, you can create virtual Search Folders that are automatically updated.

Finding E-Mail Messages

If you are having trouble locating a particular message in your Inbox or another message folder, you can search for it using Outlook’s Find or Advanced Find features. You can look for messages in a single folder, a group of folders you select, or all your folders. You can instruct Outlook to search through the text of every message or only the Subject field.

Using Search Folders

Search Folders, like Outlook’s Find feature, show all the files that match a set of search criteria, and can show files from different folders together in one place. Unlike a search conducted using the Find feature, when you create a Search Folder, it becomes part of your mailbox and is always kept up to date.

The default Outlook 2003 installation includes three Search Folders:

■ The For Follow Up folder displays messages flagged for follow-up.

■ The Large Mail folder displays messages larger than 100 kilobytes (KB), grouped by size as Large (100 – 500 KB), Very Large (500 KB – 1 MB), Huge (1 – 5 MB), and Enormous (> 5 MB).

■ The Unread Mail folder displays messages that are marked as unread.

Although Search Folders look like any other Outlook folders, they are actually virtual folders. Each message in your mailbox is stored in only one Outlook folder (such as your Inbox), but it might appear in many Search Folders. Changing or deleting a message in a Search Folder changes or deletes the message in the Outlook folder where it is stored.

Save Items in Different File Formats

Sometimes a message will contain information that you want to save or use in another program. You can save messages, calendar items, contact entries, tasks, and notes to your computer as individual files.

Saving E-Mail Messages in Other Formats

You can save a message as a plain text file, which most programs can open or import. Or you might save a message as an HTML document, which would make it easier to post it to a team portal or Web site.

Assign Items to Categories

Another way to organize and find items is to assign them to categories. With categories, you group items by a common characteristic. Outlook includes a set of predefined categories, and you can also create your own. For example, you might assign all messages about invoices and payments to the Finance category, or you might create a Payroll category for all messages related to timesheets and paychecks.

Assigning Outlook Items to Categories

You can assign all types of Outlook items to categories. There are many ways to assign items to categories, but there is one simple process that applies to all types of items.

Preview and Print Items

Many Outlook users manage a large amount of information in Outlook: e-mail messages, contact information, calendar information, general notes, and task lists. In addition to having information available electronically on a desktop, laptop, or handheld computer, it is sometimes necessary or desirable to have a hard copy, or printout, of the information stored by Outlook.

Previewing and Printing an E-Mail Message

There might be occasions when you need a hard copy, or printout, of an e-mail message. For example, you might need to print the directions to the location of an appointment or distribute copies of a message at a meeting. With Outlook, you can print your e-mail messages in much the same way you would any other document.

Depending on the format (HTML, Rich Text, or Plain Text) of the message you want to print, you can set a number of page setup options, including paper size, margins, and orientation. You can also use Print Preview to see how a message will appear when printed.

Previewing and Printing Your Outlook Calendar

When your schedule is full and you find yourself running from one appointment to the next, you might not always be able to check your Outlook Calendar. By printing your Calendar, you can take your schedule with you. You can print your Calendar in a variety of formats, called print styles. You can select from the following pre-defined print styles:

■ Daily Style prints the selected date range with one day per page. Printed elements include the date, day, TaskPad and reference month calendars, along with an area for notes.

■ Weekly Style prints the selected date range with one calendar week per page, including reference calendars for the selected and following months.

■ Monthly Style prints a page for each month in the selected date range. Each page includes the six-week range surrounding the month, along with reference calendars for the selected and following months.

■ Tri-fold Style prints a page for each day in the selected date range. Each page includes the daily schedule, weekly schedule, and TaskPad.

■ Calendar Details lists your appointments for the selected date range, as well as the accompanying appointment details.

You select the date or range of dates to be printed each time you print.

Previewing and Printing Contact Information

To make it easy to take contact information with you while you are away from your computer, you can print your Contacts list. You can print contact information from any of the available views, and for the Address Card views, you can select from a number of print styles. You can define your own print styles for all views, specifying the layout, the margins, orientation, and more. The print options available to you vary based on the view selected when you chose to print.

 

15. E-mailing program: Outlook

(Draft)

What is the e-mail?

E-mail address components

What Outlook is good for:

1. I. Messaging

a) Addressing and Sending a New E-Mail Message

b) Handling E-Mail Messages You Receive

c) Sending and Replying to Instant Messages

1. 2. Attach Files to Items

a) Attaching a File to an E-Mail Message

b) Sending a File Through an Instant Message

1. 3. Create and Modify a Personal Signature for Messages

a) Creating and Modifying an E-Mail Signature

b) Specifying Unique Signatures for Multiple E-Mail Accounts

1. 4. Modify E-Mail Message Settings and Delivery Options

a) Flagging an E-Mail Message for Follow-Up

b) Setting E-Mail Message Formats

c) Setting E-Mail Message Importance, Sensitivity, and Delivery Options

1. 5. Create and Edit Contacts

a) Creating and Updating Contact Entries

b) Creating Instant Messaging Contact Entries

1. 6. Accept, Decline, and Delegate Tasks

a) Handling Task Assignments

1. II. Scheduling
   1. 1. Create and Modify Appointments, Meetings, and Events

a) Adding an Appointment or Event to the Outlook Calendar

b) Inviting People and Resources to a Meeting

1. 2. Update, Cancel, and Respond to Meeting Requests

a) Responding to a Meeting Request

b) Updating or Canceling a Meeting

1. 3. Customize Calendar Settings

a) Setting Your Outlook Calendar Options

b) Defining Your Available Time

1. 4. Create, Modify, and Assign Tasks

a) Creating and Modifying a Task

b) Assigning a Task

III. Organizing

1. 1. Create and Modify Distribution Lists

a) Creating a Distribution List

b) Modifying a Distribution List

1. 2. Link Contacts to Other Items

a) Linking an Outlook Item to a Contact Entry

1. 3. Create and Modify Notes

a) Creating and Editing Notes

1. 4. Organize Items

a) Adding and Deleting Fields from Folder Views

b) Sorting Outlook Items

c) Filtering E-Mail Messages

d) Organizing Outlook Items by Using Colors

e) Organizing E-Mail Messages by Using Rules

f) Organizing Outlook Items by Using Views

1. 5. Organize Items Using Folders

a) Organizing E-Mail Messages in Folders

b) Archiving Outlook Items

1. 6. Search for Items

a) Finding E-Mail Messages

b) Using Search Folders

1. 7. Save Items in Different File Formats

a) Saving E-Mail Messages in Other Formats

1. 8. Assign Items to Categories

a) Assigning Outlook Items to Categories

1. 9. Preview and Print Items

a) Previewing and Printing an E-Mail Message

b) Previewing and Printing Your Outlook Calendar

c) Previewing and Printing Contact Information

 



16. The Essentials of Google Search

Doing a search on Google is easy. Simply type one or more search terms (the words or phrase that best describe the information you want to find) into the search box and hit the Enter key or click on the Google Search button.

 

In response, Google produces a results page: a list of web pages related to your search terms, with the most relevant page appearing first, then the next, and so on.

Here are some basic tips to help you maximize the effectiveness of your search:

Choosing search terms Capitalization Automatic "and" queries		Exclusion of common words Word variations Phrase searches	Negative terms Im Feeling Lucky
Choosing search terms

Choosing the right search terms is the key to finding the information you need.

Start with the obvious – if youre looking for general information on Hawaii, try Hawaii.

But its often advisable to use multiple search terms; if youre planning a Hawaiian vacation, youll do better with vacation Hawaii than with either vacation or Hawaii by themselves. And vacation Hawaii golf may produce even better (or, depending on your perspective, worse) results.

 

You might also ask yourself if your search terms are sufficiently specific. Its better to search on luxury hotels Maui than on tropical island hotels. But choose your search terms carefully; Google looks for the search terms you chose, so luxury hotels Maui will probably deliver better results than really nice places to spend the night in Maui.

 

 

Capitalization

Google searches are NOT case sensitive. All letters, regardless of how you type them, will be understood as lower case. For example, searches for george washington, George Washington, and gEoRgE wAsHiNgToN will all return the same results.

 

 

Automatic "and" queries

By default, Google only returns pages that include all of your search terms. There is no need to include "and" between terms. Keep in mind that the order in which the terms are typed will affect the search results. To restrict a search further, just include more terms. For example, to plan a vacation to Hawaii, simply type vacation hawaii.

 

 

 

Automatic exclusion of common words

Google ignores common words and characters such as "where" and "how", as well as certain single digits and single letters, because they tend to slow down your search without improving the results. Google will indicate if a common word has been excluded by displaying details on the results page below the search box.

If a common word is essential to getting the results you want, you can include it by putting a "+" sign in front of it. (Be sure to include a space before the "+" sign.)

Another method for doing this is conducting a phrase search, which simply means putting quotation marks around two or more words. Common words in a phrase search (e.g., "where are you") are included in the search.

For example, to search for Star Wars, Episode I, use:

 

~ OR ~

 

 

Word variations (stemming)

Google now uses stemming technology. Thus, when appropriate, it will search not only for your search terms, but also for words that are similar to some or all of those terms. If you search for pet lemur dietary needs, Google will also search for pet lemur diet needs, and other related variations of your terms. Any variants of your terms that were searched for will be highlighted in the snippet of text accompanying each result.

 

 

Phrase searches

Sometimes youll only want results that include an exact phrase. In this case, simply put quotation marks around your search terms.

 

Phrase searches are particularly effective if youre searching for proper names ("George Washington"), lyrics ("the long and winding road"), or other famous phrases ("This was their finest hour").

 

 

Negative terms

If your search term has more than one meaning (bass, for example, could refer to fishing or music) you can focus your search by putting a minus sign ("-") in front of words related the meaning you want to avoid.

For example, heres how youd find pages about bass-heavy lakes, but not bass-heavy music:

 

Note: when you include a negative term in your search, be sure to include a space before the minus sign.

Cached Links

Google takes a snapshot of each page examined as it crawls the web and caches these as a back-up in case the original page is unavailable. If you click on the "Cached" link, you will see the web page as it looked when we indexed it. The cached content is the content Google uses to judge whether this page is a relevant match for your query.

When the cached page is displayed, it will have a header at the top which serves as a reminder that this is not necessarily the most recent version of the page. Terms that match your query are highlighted on the cached version to make it easier for you to see why your page is relevant.

The "Cached" link will be missing for sites that have not been indexed, as well as for sites whose owners have requested we not cache their content.

Google ... Advertise with Us - Business Solutions - Services & Tools - Jobs, Press, & Help ©2004 Google - Searching 4,285,199,774 web pages. www.google.com/ - 3k - Nov 26, 2004 - » Cached « - Similar pages

 

 

Im Feeling Lucky

The "Im Feeling Lucky™" button takes you directly to the first web page Google returned for your query. You will not see the other search results at all. An "Im Feeling Lucky" search means you spend less time searching for web pages and more time looking at them.

For example, to find the homepage for Stanford University, simply enter Stanford into the search field and click on the "Im Feeling Lucky" button. Google takes you directly to "www.stanford.edu", the official homepage of Stanford University.

example:

Az űrlap teteje Az űrlap alja

Are you feeling lucky?

 

 

 

 

A keresőprogramok szolgáltatásaihoz akkor folyamodhatunk, ha valamilyen konkrét információt szeretnénk fellelni az Interneten.  A keresőprogramok néhány kulcsszó megadása után megadják adatbázisukból mindazon honlapok elérhetőségét, amelyek a kulcsszót tartalmazzák.

A keresőprogramok használatával azonban óvatosan kell bánnunk, ugyanis bár többségük valamilyen szinten rangsorolja a tárgykörhöz kapcsolódó honlapokat, de igazából nem tud különbséget tenni a ténylegesen releváns és a kevésbé fontos oldalak között.  Emellett fontos megjegyezni, hogy a keresők több millió oldalon keresnek, így ha kezelhető mennyiségű találatot (találatról beszélünk, ha a keresőben megadott információk szerepelnek kereső által felhozott honlapokon) szeretnénk kapni, igyekezzünk minél több ,minél specifikusabb kulcsszót megadni.  Ezen túlmenően a keresők különféle szűkítési lehetőségekkel is segítik az Interneten való fürkészést.

A magyar keresők közül a legfontosabbak az [origo]-n található Vizsla (www.origo.hu), valamint a Heuréka (www.heureka.hu).  A nemzetközi keresőprogramok közül említést érdemel az Altavista (www.altavista.com), a Yahoo! (www.yahoo.com), a Google (www.google.com) és a Northenlight (www.nortehnlight.com).

 

XVII. Computer network

A computer network is a system for communication among two or more computers.

Contents

1 Categorizing   1.1 By range 1.2 By functional relationship 1.3 By network topology

Categorizing

By range

• personal area network (PAN)
  • wireless PAN
• local area network (LAN)
  • wireless LAN
  • HomePNA
  • Power line communication (HomePlug)
• metropolitan area network (MAN)
• wide area network (WAN)

By functional relationship

• client-server
• multitier architecture
• Peer-to-peer

By network topology

• bus network
• star network
• ring network

 

A personal area network (PAN) is a computer network used for communication among computer devices (including telephones and personal digital assistants) close to one person. The devices may or may not belong to the person in question. The reach of a PAN is typically a few meters. PANs can be used for communication among the personal devices themselves (intrapersonal communication), or for connecting to a higher level network and the Internet (an uplink).

Personal area networks may be wired with computer buses such as USB and Firewire. Wireless PANs can also be made possible with network technologies such as IrDA and Bluetooth.

A wireless personal area network (WPAN) is a personal area network (PAN) that uses radio rather than wires.

A local area network (LAN) is a computer network covering a local area, like a home, office or small group of buildings such as a college. The topology of a network dictates its physical structure.

The generally accepted maximum size for a LAN is 1 km². LANs are different from personal area networks (PANs), metropolitan area networks (MANs) or wide area networks (WANs). LANs are typically faster than WANs.

The earliest popular LAN, ARCnet, was released in 1977 by Datapoint and was originally intended to allow multiple Datapoint 2200s to share disk storage. Like all early LANs, ARCnet was originally vendor-specific. Standardization efforts by the IEEE have resulted in the IEEE 802 series of standards. There are now two common wiring technologies for a LAN, Ethernet and Token Ring. Wireless technologies are starting to evolve and are convenient for mobile computer users.

When using Ethernet the computers are usually wired to a hub or to a switch. This constitutes the physical layer.

The Spanning tree protocol is often used to maintain a loop free network topology within a LAN, particularly with ethernet.

A number of network protocols may use the basic physical layer including TCP/IP. In this case DHCP is a convenient way to obtain an IP address rather than using fixed addressing. LANs can be interlinked by connections to form a Wide area network. A router is used to make the connection between LANs.

LANs are distinguished form other kind of networks by three characteristics: (1)their size (2)their transmission technology, and (3) their topology

 

A wireless LAN or WLAN is a wireless local area network that uses radio waves as its carrier: the last link with the users is wireless, to give a network connection to all users in a building or campus. The backbone network usually uses cables.

WLAN is expected to continue to be an important form of connection in many business areas. The market is expected to grow as the benefits of WLAN are recognized. Frost and Sullivan estimate the WLAN market to have been 0.3 billion US dollars in 1998 and 1.6 billion dollars in 2005. So far WLANs have been installed in universities, airports, and other major public places. Decreasing costs of WLAN equipment has also brought it to many homes. However, in the UK the exorbitant cost of using such connections in public has so far limited use to airports Business Class lounges, etc. Large future markets are estimated to be in health care, corporate offices and the downtown area of major cities. New York City has even begun a pilot program to cover all five boroughs of the city with wireless Internet.

HomePNA is also known as HPNA, Home PNA, Home Phone line Networking Alliance, Home Phone line Networking and HomePNA. David Thomasson, its marketing chair says: "I wish we could redial and go back and rename this whole technology, but were stuck with it." Some blame this confusion for the earlier versions of HomePNA being ignored.

Power line communication (PLC), also called Broadband over Power Lines (BPL), is wireline method of communication using the existing electric power transmission and electricity distribution lines. The carrier can communicate voice and data by superimposing an analogue signal over the standard 50 or 60 Hz alternating current (AC).

Metropolitan Area Networks or MANs are large computer networks usually spanning a campus or a city. They typically use optical fiber connections to link their sites.

For instance a university or college may have a MAN that joins together many of their local area networks (LANs) situated around site of a fraction of a square kilometer. Then from their MAN they could have several wide area network (WAN) links to other universities or the Internet.

Some technologies used for this purpose are ATM, FDDI and SMDS. These older technologies are in the process of being displaced by Gigabit Ethernet-based MANs in most areas. MAN links between LANs have been built without cables using either microwave, radio, or infra-red free-space optical communication links.

DQDB, Distributed Queue Dual Bus, is the Metropolitan Area Network standard for data communication. It specified in the IEEE 802.6 standard. Using DQDB, networks can be up to 30 miles long and operate at speeds of 34 to 155 Mbps.

A wide area network or WAN is a computer network covering a wide geographical area, involving vast array of computers. This is different from personal area networks (PANs), metropolitan area networks (MANs) or local area networks (LANs) that are usually limited to a room, building or campus. The best example of a WAN is the Internet.

WANs are used to connect local area networks together, so that users and computers in one location can communicate with users and computers in other locations. Many WANs are built for one particular organization and are private, others, built by Internet service providers provide connections from an organizations LAN to the Internet. WANs are most often built of leased lines. At each end of the leased line, a router connects to the LAN on one side and a hub within the WAN on the other. A number of network protocols may use the basic physical transport mechanism including TCP/IP. Other protocols including X.25, ATM and Frame relay can also be used for WANs.

Now that the Internet provides a high speed WAN, the need for a private network made up of leased lines owned by the organization which wants to connect the sites has decreased. Virtual private networks are often used instead. These use encryption and other techniques to make it appear that the organization has a dedicated network while making use of the shared infrastructure of the WAN.

 

Client/Server is a scalable architecture whereby each computer or process on the network is either a client or a server. Server software generally but not always runs on powerful computers dedicated for exclusive use to running the business application. Client software on the other hand generally runs on common PCs or workstations. Clients get all or most of their information and rely on the application server for things such as configuration files, stock quotes, business application programs or to offload compute intensive application tasks back the server to keep the client computer (and client computer user) free to perform other tasks.

Properties of a server:

• Passive (Slave)
• Waiting for requests
• On requests serves them and send a reply

Properties of a client:

• Active (Master)
• Sending requests
• Waits until reply arrives

Servers can be stateless or stateful. A stateless server does not keep any information between requests. Example: An HTTP server for static HTML pages. A stateful server can remember information between requests. The scope of this information can be global or session. Example: Apache Tomcat.

The interaction between client and server is often described using sequence diagrams. Sequence diagrams are standardized in the UML.

Another type of network architecture is known as a peer-to-peer architecture because each node or instance of the program is both a client and a server and each has equivalent responsibilities. Both client/server and peer-to-peer architectures are in wide use. Each has advantages and disadvantages.

In software engineering, a multi-tier architecture is used to describe one in which a degree of separation is attained by one or many software agents between discrete components in order to facilitate processing in some manner. An example of this would be the use of middleware to more efficiently service data requests between a user and a database. May also be referred to as an n-tier architecture. The most widespread use of this term refers to the three-tier architecture.

A peer-to-peer (or P2P) computer network is a network that relies on computing power at the edges (ends) of a connection rather than in the network itself.

A pure peer-to-peer file transfer network does not have the notion of clients or servers, but only equal peer nodes that simultaneously function as both "clients" and "servers" to the other nodes on the network. This model of network arrangement differs from the client-server model where communication is usually to and from a central server. A typical example for a non peer-to-peer file transfer is an FTP server. One user uploads a file to the FTP server, then many others download it, with no need for the uploader and downloader to be connected at the same time.

Some networks and channels, such as Napster, OpenNap, or IRC @find, use a client-server structure for some tasks (e.g. searching) and a peer-to-peer structure for others. Networks such as Gnutella or Freenet, use a peer-to-peer structure for all purposes and are sometimes referred to as true peer-to-peer networks, though Gnutella at least is greatly facilitated by directory servers which inform peers of the network addresses of other peers.

Peer-to-peer architecture embodies one of the key technical concepts of the internet, described in the first internet RFC, "RFC 1, Host Software" dated 7 April 1969. More recently the concept has achieved wide prominence among the general public in the context of the absence of central indexing servers in architectures used for exchanging multimedia files.

 

A network may be represented as a collection of nodes, some of which are connected by links. A given node may have links to many others (see diagrams below). Network topology is determined only by the configuration of connections between nodes; it is therefore a part of Graph theory. Distances between nodes, physical interconnections, transmission rates, and/or signal types are not a matter of network topology, although they may be affected by it in an actual physical network.

The common types of network topology are illustrated and defined below.

A fully connected or complete topology is a network topology in which there is a direct link between all pairs of nodes. In a fully connected network with n nodes, there are n(n-1)/2 direct links. Synonym fully connected mesh network.

Bus topology : A bus network is such that there is a single line (the bus) to which all nodes are connected, and the nodes connect only to this bus.

Linear topology: See Bus topology.

Mesh topology: A network topology in which there are at least two nodes with two or more paths between them. A special kind of mesh, limiting the number of hops between two nodes, is a hypercube. The number of arbitrary forks in mesh networks makes them more difficult to design and implement, but their decentralized nature makes them very useful.

Ring topology: A network topology in which every node has exactly two branches connected to it. These nodes and branches form a ring. If one of the nodes on the ring fails then the ring is broken and cannot work. A dual ring topology has four branches connected to it, and is more resistant to failures.

Star topology: A network topology in which peripheral nodes are connected to a central node, which rebroadcasts all transmissions received from any peripheral node to all peripheral nodes on the network, including the originating node. All peripheral nodes may thus communicate with all others by transmitting to, and receiving from, the central node only.

The failure of a transmission line linking any peripheral node to the central node will result in the isolation of that peripheral node from all others.

If the star central node is passive, the originating node must be able to tolerate the reception of an echo of its own transmission, delayed by the two-way transmission time (i.e. to and from the central node) plus any delay generated in the central node. An active star network has an active central node that usually has the means to prevent echo-related problems.

Tree topology: A network topology in which the nodes are arranged as a tree. From a purely topologic viewpoint, this resembles an interconnection of star networks in that individual peripheral nodes (i.e. leaves) are required to transmit to and receive from one other node only and are not required to act as repeaters or regenerators. Unlike the star network, the function of the central node may be distributed.

As in the conventional star network, individual nodes may thus still be isolated from the network by a single-point failure of a transmission path to the node. If a link connecting a leaf fails, that leaf is isolated; if a connection to a non-leaf node fails, an entire section of the network becomes isolated from the rest.

A hybrid topology is a combination of any two or more network topologies in such a way that the resulting network does not have one of the standard forms. For example, a tree network connected to a tree network is still a tree network, but two star networks connected together exhibit hybrid network topologies. A hybrid topology is always produced when two different basic network topologies are connected.

Pages on Network card, wires:

http://en.wikipedia.org/wiki/Network_card

http://en.wikipedia.org/wiki/Computer_network

 

19-20-21 Library

 

In its traditional sense, a library is a collection of books and periodicals. It can refer to an individuals private collection, but more often, it is a large collection that is funded and maintained by a city or institution. This collection is often used by people who choose not to, or can not afford to purchase an extensive collection themselves. However, with the collection or invention of media other than books for storing information, many libraries are now also repositories and/or access points for maps, prints or other artwork, microfilm, microfiche, audio tapes, CDs, LPs, video tapes and DVDs, and provide public facilities to access CD-ROM databases and the Internet.

 

Thus, modern libraries are increasingly being redefined as places to get unrestricted access to information in many formats and from many sources.

 

Types of libraries

 

Many libraries are comfortable places for reading and studying.

 

Libraries can be divided into categories by several methods:

by the entity (institution, municipality, or corporate body) that supports or perpetuates it

• private libraries
• corporate libraries
• federal libraries
• academic libraries
• historical society libraries

by the type of documents or materials it holds

• digital libraries
• picture (photograph) libraries
• slide libraries
• tool libraries

by the subject matter of documents it holds

• architecture libraries
• fine arts libraries
• military libraries
• law libraries

by the users it serves

• military communities

by traditional professional divisions:

• Academic libraries -- These libraries are located on the campuses of colleges and universities and serve primarily the students and faculty of that and other academic institutions.
• School libraries -- Most public and private primary and secondary schools have libraries designed to support the curriculum.
• Public libraries or public lending libraries -- These libraries provide service to the general public and make at least some of their books available for borrowing, so that readers may use them at home over a period of days or weeks. Many public libraries also serve as community organizations that provide free services and events to the public, particularly children.
• Special libraries -- All other libraries fall into this category by default. Many private businesses and public organizations, including hospitals, museums, research laboratories, law firms, and many government departments and agencies, maintain their own libraries for the use of their employees in doing specialized research related to their work. Special libraries may or may not be accessible to some identified part of the general public.

 

Also, the governments of most major countries support national libraries. Two noteworthy examples are the U.S. Library of Congress and the British Library.

 

History

 

The first libraries were only partly libraries, being composed for the most part of the unpublished records that make up archives. Archaeological findings from the diggings of the ancient city-states of Sumer have revealed temple rooms full of clay tablets in cuneiform script. These archives were made up nearly completely of the records of commercial transactions or inventories, with only a few documents touching theological matters or legends. Things were much the same in the Papyrus based government records of Ancient Egypt.

 

Private or personal libraries made up of non-fiction and fiction books, (as opposed to the state or institutional records kept in archives) first appeared in classical Greece. The first ones appeared some time near the 5th century before our era. They were filled with parchment scrolls and later on papyrus scrolls. There were a few institutional or royal libraries like the Library of Alexandria, which were open to an educated public but on the whole, collections were private. In those rare cases where it was possible for a scholar to consult library books there seems to have been no direct access to the stacks. In all recorded cases the books were kept in a relatively small room where the staff went to get them for the readers, who had to consult them in an adjoining hall or covered walkway.

 

Little is known about early Chinese libraries, save what is written about the imperial library which began with the Qin Dynasty. One of the curators of the imperial library in the Han Dynasty is believed to have been the first to establish a library classification system and the first book notation system. At this time the library catalog was written on scrolls of fine silk and stored in silk bags.

 

The medieval library arose very directly from the fact that books were valuable possessions, were therefore likely to be stolen, and were far too expensive for most people to own. Its architecture derived from the need to chain these books, first to lecterns and later to armaria and shelves, in areas that were illuminated by sunlight. Early libraries were located in monastic cloisters associated with scriptoria and were collections of lecterns with books chained to them. Shelves built above and between back-to-back lecterns were the beginning of bookpresses. The chain was attached at the fore-edge of a book rather than to its spine.

 

As books became cheaper, the need for chaining them lessened, but as the number of books in libraries increased, so did the need for compact storage and access with adequate lighting, giving birth to the stack system, which involved keeping a librarys collection of books in a space separate from the reading room, an arrangement which arose in the 19th century.

 

Matthias Corvinus of Hungary’s Libary

 

His library, the Bibliotheca Corviniana, was Europes greatest collection of historical chronicles and philosophic and scientific works in the 15th century, and second only in size to the Vatican library.

 

Description/Services

 

Libraries usually have nearly every item they own arranged in a specified order according to a library classification system, so that particular items may be located quickly and collections may be browsed efficiently. Some libraries have additional galleries beyond the public ones, where reference materials are stored. These reference stacks may be open to selected members of the public; others require patrons to submit a "stack request," which is a request for a librarian to find the material in the stacks and bring it out to the patron. Libraries often feature a professional librarian working from a reference desk or other central location to help users find what they are looking for.

 

Dewey Decimal Classification

 

The Dewey Decimal Classification (DDC, also called the Dewey Decimal System) is a system of library classification developed by Melvil Dewey (1851–1931) in 1876, and since greatly modified and expanded in the course of the twenty-two major revisions which have occurred up until 2004.

 

How it works

 

The DDC attempts to organize all knowledge into ten main classes that, excluding the first class (000 Computers, information and general reference), proceed from the divine (philosophy & religion) to the mundane (history & geography). DDCs cleverness is in choosing decimals for its categories; this allows it to be both purely numerical and infinitely hierarchical. It also is a faceted classification, combining elements from different parts of the structure to construct a number representing the subject content (often combining two subject elements with linking numbers and geographical and temporal elements) and form of an item rather than drawing upon a list containing each class and its meaning.

 

Except for general works and fiction, works are classified principally by subject, with extensions for subject relationships, place, time or type of material, producing classification numbers of not less than three digits but otherwise of indeterminate length with a decimal point before the fourth digit, where present (e.g. 330 for economy + 94 for Europe = 330.94 European economy; 973 for United States + 005 form division for periodicals = 973.005, periodicals concerning the United States generally); classmarks are to be read as numbers, in the order: 050, 220, 330.973, 331 etc. Any letter should be read as preceding any number that might have occupied the same character position, so "330.94 A" would come before 330.943. The system uses ten main classes, which are then further subdivided. Each main class has ten divisions and each division has ten sections. Hence the system can be neatly summarized in 10 main classes, 100 divisions and 1000 sections. It is a common misconception that all books in the DDC are non-fiction. However, the DDC has a number for all books, including those that generally become their own section of fiction. If DDC rules were strictly followed, American fiction would be classified in 813. Most libraries create a separate fiction section because of the space that would be taken up in the 800s.

 

Main classes

 

The system is made of up ten categories:

000 Computers, information and general reference

100 Philosophy and psychology

200 Religion

300 Social sciences

400 Language

500 Science and mathematics

600 Technology

700 Arts and recreation

800 Literature

900 History and geography

 

Library use

 

Libraries must inform the public of what materials are available in their collections, and the public must know how to access that information. Before the computer age, this was accomplished by the card catalog -- a piece of wooden or metal furniture containing many drawers, each filled with standard-sized index cards identifying books and other materials. In a large library, the card catalog units often filled a large room, or else lined most hallways in the building. The emergence of the Internet, however, has led to the adoption of electronic catalog databases (often referred to as "webcats" or as OPACs, for "online public access catalog"), which allow users to search the librarys holdings from any location with Internet access. This style of catalog maintenance is compatible with new types of libraries, such as digital libraries and distributed libraries, as well as older libraries that have been retrofitted.

 

Transition to digital format

 

The term e-book (electronic book) in the broad sense is an amount of information like a conventional book, but in digital form. It is made available through internet, CD-ROM, etc. In the popular press the term eBook sometimes refers to a device such as the Sony Librie EBR-1000EP, which is meant to read the digital form and present it to a human being.

 

Throughout the 20th century, libraries have faced an ever-increasing rate of publishing, sometimes called an information explosion. The advent of electronic publishing and the Internet means that much new information is not printed in paper books, but is made available online e.g. through a digital library, on CD-ROM, or in the form of e-books.

 

On the other hand, though books are nowadays produced using a digital version of the content, for most books such a version is not available to the public (i.e. neither in the library nor on internet), and there is no decline in the rate of paper publishing. There is an effort, however, to convert books that are in the public domain into a digital medium for unlimited redistribution and infinite availability. The effort is spearheaded by Project Gutenberg combined with Distributed Proofreaders.

 

There have also been new developments in the process of publishing books. Technologies such as print on demand have made it easier for less known authors to make their work available to a larger audience.

 

Some famous libraries:

 

• Assurbanipals library at Nineveh
• Bibliothèque Nationale de France (BNF) in Paris
• Bodleian Library at University of Oxford
• British Library in London
• Cambridge University Library at University of Cambridge