Computer Studies Form 5

COMPUTER STUDIES NOTES

1. PROGRAMMING LANGUAGES There are two main types of languages which are the High-level language and the Low-level language.

HIGH-LEVEL LANGUAGE: The High-level languages are theoretically machine-independent which means they are mainly machine code. The High-level languages are more powerful than the low-level languages. This language is used quite frequently; it is used in the PASCAL program and other programming software such as the BASIC. This language is written in English and also in machine code, this means it isn’t that difficult to learn and to begin with. Students usually begin learning and working with these high-level languages because it is easy to learn. Ultimately programs written in high-level language must be translated into machine language by a compiler or an interpreter. These languages are often described as problem-oriented languages.

LOW-LEVEL LANGUAGE: There are also the low-level languages which are more suited to sophisticated techniques because only machine code is used in them.

These languages are harder to learn and to work on obviously. The low-level language is faster in execution then the high-level language and uses less memory when saved. These languages are not generally good for problem solving programs but are good for writing translator programs. These languages are also known and described as machineoriented languages. The low-level language is closer to the hardware than the human language. Two good examples of low-level languages are the Assembly language and the machine code.

TRANSLATORS: There are three types of translators which are the Assembler, the Interpreter and the Compiler.

THE ASSEMBLER: The assembler is some kind of software which translates the assembly language of the computer to machine code. The process when the assembly language is being translated to machine code is

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called assembly. The assembler program is specific to a type of computer and is often provided as part of the systems software.

THE INTERPRETER: The interpreter translates and executes a program one statement at a time. The interpreter is actually a machine code program. It is used as an easy way of executing programs not in the machine code of the computer. Sometimes the interpreter may be slow, for example when an interpreted program contains a loop the speed will decrease because the analysis of each statement has to be repeated for each time round the loop.

THE COMPILER: Last but not least is the compiler. The compiler is a simple program which translates a high-level language program into a computer’s machine code or some other low-level language. The translation process is called compilation. The compilation involves the analyzing of the language structure of the source program checking if it is valid and then producing suitable machine code.

SOURCE CODE AND OBJECT CODE Source code and object code refer to the "before" and "after" versions of a computer program that is compiled. The source code consists of the programming statements that are created by a programmer with a text editor or a visual programming tool and then saved in a file.

For example, a programmer using the ‘A’ language types in a desired sequence of ‘A’ language statements using a text editor and then saves them as a named file. This file is said to contain the source code. It is now ready to be compiled with an ‘A’ compiler and the resulting output, the compiled file, is often referred to as object code.

The object code file contains a sequence of instructions that the processor can understand but that is difficult for a human to read or modify. For this reason and because even debugged programs often need some later enhancement, the source code is the most permanent form of the program.

Source code – is the program written by the programmer in a programming language.

Object code – is the translation of the program into machine code done by the compiler or interpreter and ready for execution.

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A program is written as a series of human understandable computer instructions that can be read by a compiler and linker, and translated into machine code so that a computer can understand and run it.

A computer ‘works’ by executing a series of instructions – the program. A program can be written in a variety of programming languages. In order of development there are several ‘generations’ of languages: Machine & Assembly Language

Low-level languages

PASCAL / BASIC / C++

High Level Languages

High-Level & Low-Level Languages –> TRANSLATED TO Machines Language

MACHINE CODE A manufacturer designs a computer to obey just one language, its machine code, which will be represented inside the computer by combinations of binary digits. The set of binary codes which can be recognized by the computer is known as the machine code instruction set.

INSTRUCITON FORMAT The instruction format of a machine code instruction has two main parts: • A function (or operation) opcode; • An address (operand).

e.g.

Op. code

Operand address

0 0 1 1

0 0 0 0 0 0 0 0 1 0

The function code tells the control unit of the CPU what to do with the item held in the address.

For example, for one computer: 4 A 2

Instruction (op. code) MR NOEL ATTARD

187 Address PAGE: 3

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might be the hexadecimal machine code instruction for: ‘add the contents of storage location 187 to the contents of register 2’.

The absolute address of each store location is a binary number which can be decoded so that when data is required from a memory cell the right location is selected.

LOW-LEVEL LANGUAGES Programming of the first stored-program computer systems was performed in machine language. This is the lowest level of programming language. All the commands and data values are given in ones and zeros, corresponding to the "on" and "off" electrical states in a computer. The programming process became easier with the development of assembly language, a language that is logically equivalent to machine language but is easier for people to read, write, and understand. But the limitations of the low-level languages – machines code and assembly – led to the development of high-level languages which are: • • • •

‘user friendly’ (people based); similar to English with vocabularies of words and symbols; ‘problem’ rather than ‘machine’ based; shorter than their low-level equivalents – one statement translates into many machine code instructions.

HIGH-LEVEL LANGUAGES A programming language in which the program statements are not closely related to the internal characteristics of the computer is called a high-level language. As a general rule, one statement in a high-level programming language will expand into several machine language instructions. This is in contrast to assembly languages, where one statement normally generates one machine language instruction.

Example: PASCAL , BASIC, C++

PROGRAMMING LANGUAGE GENERATIONS In the computer industry, these abbreviations are widely used to represent major steps or "generations" in the evolution of programming languages.

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1GL OR FIRST-GENERATION LANGUAGE – Low Level The first generation of programming language is a machine-level language that makes use of the binary system (0 and 1) as codes for the program. The system would then convert these codes into instructions. Machine-level language was fairly quick in execution since it is directly instructed by the CPU; however it is fairly confusing to learn and to edit since the programming language uses numerical representations of instructions that do not appear significant to a human user.

Example: Machine code

2GL OR SECOND-GENERATION LANGUAGE – Low Level The second generation of programming language makes use of assembly language, meaning, it has a slight similarity with the human language, although it has to be converted into machine language (the binary system) in order to be executed. Each command is mapped into a set of binary codes, which the CPU performs in a similar way that it executes machine-level language. Normally an assembly language statement consists of a label, an operation code, and one or more operands. Labels are used to identify and reference instructions in the program. The operation code is a symbolic notation that specifies the particular operation to be performed, such as move, add, subtract, or compare. It has a significant speed advantage, although machine-level language is still quicker in execution due to its direct instruction into the CPU.

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The assembler (sometimes called "assembly") language is a typical 2GL instruction looks like this: ADD

12,8

An assembler then converts the assembler language statements into machine language, before instruction is executed, as the computer ONLY UNDERSTANDS MACHINE CODE. Example: Assembler

3GL OR THIRD-GENERATION – High Level

Third generation programming languages are designed for easier human use. General representations of human arithmetic and other logical operations are represented in third generation languages. 3GL language is a "high-level" programming language, such as Pascal, C, or Java. Java language statements look like this: public evt) {

boolean

handleEvent

(Event

switch (evt.id) { case Event.ACTION_EVENT: { if .equald(evt.arg)) {

("Try

me"

A compiler converts the statements of a specific high-level programming language into machine language. (In the case of Java, the output is called byte code which is converted into appropriate machine language by a Java virtual machine that runs as part of an operating system platform.) A 3GL language requires a considerable amount of programming knowledge. Programs are shorter then the other 1st & 2nd generation, and more easier to debug and transportable on different machines.

Example: Pascal, Java

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4GL OR FOURTH-GENERATION LANGUAGE – High Level Fourth generation programming languages were made to remedy the third generation language's flaws. While third generation languages performed complex functions in the program, the fourth generation language's objective was to lessen the error and quicken the process of the execution of the commands. This kind of language was designed for specific purposes, such as mathematical problem solving or systems engineering. An example of a 4GL is the query language that allows a user to request information from a database with precisely worded English-like sentences. A query language is used as a database user interface and hides the specific details of the database from the user. 4GL is designed to be closer to natural language than a 3GL language. Languages for accessing databases are often described as 4GLs. A 4GL language statement might look like this: EXTRACT ALL CUSTOMERS WHERE "PREVIOUS PURCHASES" TOTAL MORE THAN $1000

Example: Visual Basic, MS Access

5GL OR FIFTH-GENERATION LANGUAGE – High Level The fifth generation programming language was designed generally for the user's ease.

The user does not specifically need to create an entirely new program, since the language is designed to solve the problems based on user input. The user does not need to worry about making the program; the program readily performs the required routine and algorithm with the necessary input. Fifth generation language is involved with artificial intelligence research. 5GL is programming that uses a visual or graphical development interface to create source language that is usually compiled with a 3GL or 4GL language compiler. Microsoft, Borland, IBM, and other companies make 5GL visual programming products for developing applications in Java, for example. Visual programming allows you to easily envision object-oriented programming class hierarchies and drag icons to assemble program components.

Example: Lisp

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OBJECT-ORIENTED LANGUAGES In object-oriented programming, a program is no longer a series of instructions, but a collection of objects. These objects contain both data and instructions, are assigned to classes, and can perform specific tasks. With this approach, programmers can build programs from pre-existing objects and can use features from one program in another. This results in faster development time, reduced maintenance costs, and improved flexibility for future revisions. Some examples of object-oriented languages are: C, Java, and Ada

TRANSLATORS TO MACHINE LANGUAGE Is a computer program used to convert a program from one language to another (for example from a low-level language to machine code).

This is general name for the three types of translation programs, assemblers , compilers and interpreters.

Source program Low-level language

Translator

Object Program

Assembler

Assembly Machine Language High-level language E.g. BASIC, COBOL

Interpreter or Compiler

TRANSLATORS FOR LOW LEVEL LANGUAGES ASSEMBLER: The translation program needed to translate mnemonics (the assembly code) into machine code, as at the end computers only understand MACHINE CODE. TRANSLATORS FOR HIGH LEVEL LANGUAGES INTERPRETER: The interpreter translates and executes each instruction at a time.

The program runs slower since it is being translated to machine code during runtime. Debugging is easier since the interpreter stops on encountering an error.

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COMPILER: The compiler translates the whole program completely, and then executes the machine language version. When using a compiler a programmer ends up with 2 versions of the program – the source code and the object code (.exe). The program executes faster.

Compile-time errors are listed at the end of program compilation.

SOFTWARE COPYRIGHT LAW In the US, unauthorized duplication of computer software products for simultaneous use constitutes copyright infringement and is punishable in a federal criminal action pursuant to 17 U.S.C. Section 506(a) by a fine of up to $25,000 and imprisonment for up to one year. In addition, federal civil penalties provided in 17 U.S.C. Section 504(c) allow the recovery of actual damages based upon the number of copies produced, or statutory damages.

Where the copyright owner proves that infringement was willful, the court has discretion to increase the award of statutory damages up to $100,000 for each copyrighted product, which has been infringed.

Finally, 17 U.S.C. Section 505 provides for the recovery of attorney’s fees by the prevailing party.”

SOFTWARE LICENCE AGREEMENT A software license agreement is a contract between the "licensor" and purchaser of the right to use software. The license may define ways under which the copy can be used, in addition to the automatic rights of the buyer including the first sale doctrine and 17 U.S.C. § 117 (freedom to use, archive, re-sale, and backup).

Many form contracts are only contained in digital form, and only presented to a user as a click-through where the user

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2. OPERATING SYSTEM WHAT IS THE OPERATING SYSTEM / SYSTEM SOFTWARE? An operating system is a software program that provides an interface between the user and the computer and manages thousands of applications.

Most computer systems are sold with an operating system installed. Computers that are designed for individual users are called Personal Computers (PCs). PC operating systems are designed to control the operations of programs such as Web browsers, word processors, and e-mail programs.

The operating system is stored on disk, but it needs to be loaded into memory (RAM) once the computer is switched on and before any other program can be run. The operating system is automatically loaded into memory as soon as you turn on, or boot, the computer. The term booting refers to the process of loading an operating system into a computer’s memory. This process is done by a program (called the bootstrap loader) that is stored permanently in the computer’s electronic circuitry (usually on a ROM chip).

If you have a computer, then you have heard about operating systems. Any desktop or laptop PC that you buy normally comes preloaded with Windows XP. Macintosh computers come pre-loaded with OS X. Many corporate servers use the Linux or UNIX operating systems. The operating system (OS) is the first thing loaded onto the computer -- without the operating system, a computer is useless.

BASIC FUNCTIONS OF ANY OPERATING SYSTEM? Every computer has an operating system and, regardless of the size and complexity of the computer and its operating system, all operating systems perform the same basic functions: •

Managing Resources – These programs coordinate all the computer’s resources including keyboard, mouse, printer, monitor, storage devices and memory.

An operating system creates a file structure on the computer hard drive where user data can be stored and retrieved. When a file is saved, the operating system saves it, attaches a name to

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it, and remembers where it put the file for future use. The way an operating system organizes information into files is called the file system.

Most operating systems use a hierarchical file system, which organizes files into directories (folders) under a tree structure. The beginning of the directory system is called the root directory.

Screenshot of tree structure when using Windows Explorer.

•

Providing a user interface – Users interact with application programs and computer hardware through a user interface.

Almost all operating systems today provide a windows-like Graphical User Interface (GUI) in which graphic objects called icons are used to represent commonly used features.

•

Running applications – These programs load and run applications such as word processors and spreadsheets. Most operating systems support multitasking, or the ability to run more than one application at a time. When a user requests a program, the operating system locates the application and loads it into the primary memory or RAM of the computer. As more programs are loaded, the operating system must allocate the computer resources.

•

Support for built-in utility programs –The operating system uses utility programs for maintenance and repairs. Utility programs help identify problems, locate lost files, repair damaged files, and backup data. The figure here shows the progress of the Disk Defragmenter, which is found in Programs > Accessories > System Tools.

Utility Programs are specialized programs that make computing easier. All kinds of things can happen to a computer system – hard disks can crash, viruses can invade a system, computers can freeze up, operations can slow down, and so on. That’s where utility programs come in.

Many operating systems (such as Windows) have utility programs built in for common purposes – they are also known as System Tools ( to find these tools, click on Start / Programs / Accessories / System Tools ). Examples of utility programs are Format, Scan Disk, Disk Cleanup, Disk Defragmenter, and Anti-Virus.

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The purpose of an operating system is to organize and control hardware and software so that the device it lives in behaves in a flexible but predictable way.

So the essential facilities the operating system must provide are: • •

To manage all computer resources and maximise their use. (memory, peripherals, etc …)

To virtualise all the hardware to make the user life easier to communicate with the computer hardware (using printers, file and folders, etc…)

In order to do provides these features the operating system have a number of modules (small programs) to carry out these tasks. Among of these modules one finds the:

RESIDENT LOADER: It is a program responsible to load/copies a program from or to the backing store onto the central memory for eventually use. At start up not all the operating system modules are loaded, just the important modules are loaded. So if required the resident loader will need to also load the specific module when needed.

COMMAND PROCESSOR: it is the program which execute the commands. It is important to remember that a computer can only execute programs so the program (module) which execute these commands (ex: LOAD / CREATE / PRINT / OPEN) is called the command processor. Commands given by the user can be: • •

CLI – Command line Interface – typing the commands name.

GUI – Graphical User Interface – click on graphical icons.

FILE MANAGER: A file is a collection of information accessible by a name defined by the user. The file name given by the user is called the SYMBOLIC ADDRESS of a file. It is very inconvenient for a user to also remember when the file is stored on the disk and other information on the file. All the other information on the file is called the PHYSICAL ADDRESS of a file. So the uses just uses the Symbolic Address to access a file (the name), while the file manager needs the Physical Address of that file to open. So is the job of the

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file manager module to search in the list of names and address stored in the file directory when a particular file is need.

The physical file directory layout can be either chained or indexed.

The structure of the directory will include: • • • • •

File name and File Type Pointer to First Sector or to Index of file Number of sectors occupied Date of creation and last accessed Protection key

The file manager must also know which sector on disk are free or not.

This is mapped by the BIT MAP – where a 1 = used and 0 = free for each sector on disk. So when files are stored/edited or deleted the file manger will have to update the Bit Map of disk.

PERIPHERAL DRIVER: This module is responsible to check and see that every peripheral connected to the computer have the correct driver installed. The driver software is a software supplied by the manufactured so that the computer would know how to communicate with this peripheral, which the need for the user to communicate directly with is peripheral.

TYPES OF OPERATING SYSTEMS The precise nature of an operating system will depend on the application in which it is to be used. For example, the characteristics required for an airline seat reservation system will differ from those required for the control of scientific experiments, or for a desktop computer. Clearly, the operating system design must be strongly influenced by the type of use for which the computer system is intended. Unfortunately it is often the case with ‘general purpose machines’ that the type of use cannot easily be identified; a common criticism of many systems is that, in attempting to be all things to all individuals, they end up being totally satisfactory to no one. We shall examine various types of system and identify some of their characteristics.

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SINGLE USER SYSTEM: Single user systems, as their name implies, provide a computer system for only one user at a time. They are appropriate for computer dedicated to a single function, or which are so inexpensive as to make sharing not worthwhile. Single user systems generally provide a simple computer system, which facilitates the running of a variety of software packages (e.g. word processing or spreadsheet) as well as allowing uses to develop and execute programs of their own

BATCH PROCESSING: Batch processing was the first operating system – which consisted of ONE user and ONE CPU. The main purpose of this system was to enable the computer to move automatically from one job to another, without the operator having to intervene.

In any computer system, the speed by which the CPU can execute instructions is much higher than that which other peripheral devices can reach.

Thus, peripheral devices such as the printer, disk drives, and others, waste a lot of the CPU’s time, because they cannot process their part of the job as quickly as the CPU. This results in a large percentage of CPU idle time.

Another inefficiency is that, when a small program is being run, most of main memory remains unused.

Therefore, the most two expensive resources of the system – memory and time – are wasted. As processing speed and memory size increased with the advance in technology, the wastage became even greater. This is operating systems why continued to evolve from the simple batch system.

So in batch processing jobs (that consist of data and programs) are queued. The computer would then process the jobs one at a time without further human intervention. Batch processing is still used nowadays – e.g. printing thousands of mailing labels or calculating all the telephone bills of the customers.

MULTIPROGRAMMING SYSTEM: The multiprogramming operating system could manage resources more efficiently. More than one user’s program can be resident in main memory at one time. In this system we also have ONE User and ONE CPU. MR NOEL ATTARD

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In this system, multiple jobs are loaded into the central memory, and each is allotted some CPU-TIME, a tiny fraction of a second during which it receives the CPU’s attention. When a job’s CPU-TIME is up, it is suspended and control passes to the next job, which can continue from where it left off before. The TIME allocated to a job is called the TIME SLICE. In simpler terms the CPU is switched rapidly between the different programs. This means the system does not have to wait for one job to be completed before starting the next. When then for example one of the jobs is used a peripheral device - like printer to print, it TIME SLICE is given to the other jobs The simplest multiprogramming systems used a round-robin method, where each job received the same CPU-TIME. More sophisticated systems allowed priorities to be defined for each job, such that the job with the highest priority received the longest CPU-TIME. Such a system minimizes the amount of idle time of the CPU and the amount of unused memory.

A complication arises when printing. What happens when two jobs are working concurrently (at the same time) and both are printing their results? A technique known as SPOOLING is adopted, where each job sends any output to be printed to a spooler file on backing storage instead of directly to the printer.

This spool file makes a queue of all files to be printed… at a first come first served bases.

The general idea behind multiprogramming is that the computer is working on several programs, which are in memory at one time.

TIME-SHARING SYSTEM (MULTI-USER): In an interactive system, the user sits at a terminal, which is hooked up to the computer. The user can execute the job, and the output is expected to be reasonably instantaneous, even if other users are executing their own jobs on the same computer. So in this system we have MORE the one user but only ONE CPU. To meet these situations, the principle of time-sharing was introduced in the design of operating systems. The

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aim of a time-sharing operating system is to give each terminal user a response time (called time-slice) of about three to five seconds – like in multiprogramming system.

One must consider that even the fastest typist is slower that the CPU, and most people are not fast typists. Sometimes, several seconds or minutes might pass by while the user is deciding what to do next, or while thinking about the cause of an error in the program. The operating system would therefore poll each terminal every one or two seconds – that is, the computer makes an enquiry at the terminal by checking if any characters are present in the keyboard buffer. So the function of the keyboard buffer is to store any commands given by the user while the CPU attention was given to the other jobs. If there has been no activity since the last polling, the computer simply goes on to the next terminal. But if a new command has been issued, the computer will allocate a time-slice to the user. During this time, the computer devotes the full attention to this user. When the time slice is up or the user’s requests have been satisfied, the computer goes on the next terminal.

A time-sharing system works on the same principles as a multiprogramming system, so when a user will start using the peripheral device, its time slice is given to the other users. The jobs to be outputted are then saved in the Spooler file and then executed one by one like in the multiprogramming system.

REAL-TIME SYSTEMS: Immediate processing and up-to-date information are major characteristics of a real-time system. Such a system, the information in files has to be located very quickly, and the updating of records must be fast. The system must be able to respond quickly to an enquiry otherwise it becomes impractical. In a real-time system a transaction is processed to completion at the time is occurs, ensuring that the information in the files reflects the true (real) situation.

Examples of a real-time system would be: a flight reservation system, a banking situation – where data have to be processed immediately.

There is also Critique real time system, where data have to be handled

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more fast then normal timings – like in nuclear power station or space shuttle launching, were any faulty have to be shown MORE immediately then normal once.

NETWORKED SYSTEMS: As technology advanced, computers became cheap enough for all users of a system to have a microcomputer of their own. Of course, a stand-alone, single-user microcomputer can do a lot of work, but it has the following disadvantages: • Sharing data between different users becomes difficult.

• Peripherals such as printers have to be bought for each microcomputer, and will lay idle for most of the time.

Such considerations led to the development of networked systems, where many computers are connected together to facilitate the sharing of data and peripherals.

A network operating system must handle the communication between the networked computers, managing the data traffic and the sharing of system’s resources.

EXAMPLES OF OPERATING SYSTEMS SOFTWARE: • • • •

MS-DOS UNIX Linux Windows

Sometimes, software may be specific to a particular operating system and would therefore not work under a different operating system, like in the case of MAC computers. Another name for Operating System is System Software.

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3. NETWORKS NETWORKS TERMS: LAN WAN MAN TCP/IP CABLE MODEM FTP TOPOLOGY IP ADDRESS CAT 5 FIBER OPTIC CABLE BACKBONE

ETHERNET WIRELESS BPS BROADBAND

ADSL INTERNET INTRANET MAC ADDRESS CAT 6 BLUETOOTH NODE

SERVER PING PACKET HUB PROTOCOL EXTRANET VOIP COAXIAL CABLE TWISTED PAIR INFRARED SEGMENT

WHAT IS A COMPUTER NETWORK? ⇒ network is the interconnection of many computers and peripheral devices. ⇒ Networks make it possible for users to share resources for communication (hardware) and data (software) ⇒ It can be with wires or wireless

TYPES OF NETWORKS WHAT IS LAN? - Local Area Network A network in which the computer systems are all situated relatively close to each other. E.g. School Distance between the network is small What is WAN? - Wide Area Network A network in which the computers are geographically remote.

Wide area networks make use of a range of connection methods including communication satellites What is MAN? - Metropolitan Area Network A communications network that covers a geographic area such as a city or suburb or university campus.

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NETWORKS TOPOLOGIES Network topology is how nodes are connected to form a network.

POINT-TO-POINT Simplest connection. One computer connect to another computer.

BUS Each node is connected to one main communications line. With this arrangement, even if one of the nodes goes down, the rest of the network can continue to function normally. There is no hub in a bus/line network. Usually coaxial cable is used.

Adv – users uses same line, cheap & easy to do, need small lengths of cables.

Dis Adv – all terminal hear data, Terminators required at ends

STAR consists of several nodes connected to a central hub in a star-shaped configuration. Messages from individual nodes pass directly to the hub, which determines any further routing Adv – Easy to set up, No disruptions when moving devices, easy to detect faults.

Dis Adv – Requires many cables, one line disconnection will only disconnect one node, if central hub fails then network will fail.

RING Messages travel in one direction around a ring from node to node.

As each node receives a message, it checks the message address.

If the message is not for that particular node, the message is regenerated and passed on. This regeneration allows messages to travel farther in a ring network than in other network configurations.

Adding of nodes have to be done using great care.

Adv – Relatively fast, Easy to detect faults, Dis Adv – Not easy to add/remove nodes, Requires more cables, all nodes are connected to the single backbone.

TREE / HYBRID Also known as hierarchical, it is a network where bus and star topologies are combined together. The tree network, branches out into many nodes, so hubs are linked to other hubs serially.

Adv – Fast, no disruption, Easy to detect faults Dis Adv – Hard to setup, Loss of connection wire will disable lower ends nodes

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MESH / MULTI-CONNECTED Such a network is used in LANs as well as WANs. In this type of network the terminals are interconnected directly with one another.

Within LANs, mash networks are kept small. Each node acts like an intelligent hub – so able to receiver, processing and routing data.

Adv – Fastest network, No disruptions, easy to detect faults Dis Adv – Hard to setup, great amount of wires needed.

WHAT IS A BACKBONE? The main cabling (wires) of a network, to which all of the segments are connected to.

WHAT IS A NODE? Any device (with an ADDRESS) that is connected to the network

WHAT IS A HUB? A central connecting device in a network that joins communications lines together in a star configuration.

Passive hubs are just connecting units that add nothing to the data passing through them.

Active hubs, also sometimes called "multi port repeaters," regenerate the data bits in order to maintain a strong signal, and intelligent hubs provide added functionality.

WHAT IS A ROUTER? A device that forwards data packets from one local area network (LAN) or wide area network (WAN) to another.

Based on routing tables and routing protocols, routers read the network address in each transmitted frame and make a decision on how to send it based on the most expedient route (traffic load, line costs, speed, bad lines, etc.).

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WHAT IS AN IP ADDRESS? An IP address is a logical address for a network adapter. The IP address uniquely identifies computers on a TCP/IP network. An IP address can be private - for use on a local area network (LAN) - or public - for use on the Internet or other wide area network (WAN). IP addresses can be determined statically (assigned to a computer by a system administrator) or dynamically (assigned by another device on the network on demand).

WHAT IS AN MAC ADDRESS? The MAC address is a unique value associated with a network adapter.

MAC addresses are also known as hardware addresses or physical addresses. They uniquely identify an adapter on a LAN. MAC addresses are 12-digit hexadecimal numbers (48 bits in length). By convention, MAC addresses are usually written in one of the following two formats: MM:MM:MM:SS:SS:SS

MAC ADDRESSING VS IP ADDRESSING Whereas MAC addressing works at the data link layer, IP addressing functions at the network layer (layer 3). It's a slight oversimplification, but one can think of IP addressing as supporting the software implementation and MAC addresses as supporting the hardware implementation of the network stack. The MAC address generally remains fixed and follows the network device, but the IP address changes as the network device moves from one network to another.

CENTRALISED DATA: It is when data in a network is stored only one 1 computer. This is a good system as you only have to do one backup, but then if the server in down no data can be access from no one. More over as data have to pass all from one computer there might be some overloading traffic!!!

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DISTRIBUTED DATA: It is when data in a network is stored on all computer branches and not only one 1 computer. This is a good system as is one branch is down only data from that branch cannot be accessed. On the other hand each branch have to do their own backups.

WIRED AND WIRELESS COMMUNICATION: Wired •

Ribbon Cable – consist of many copper wires laid near each other to form a belt formation. Data transfer is of 160 MBps

•

Twisted Pair Cable – consist of 2 or more insulated copper wires twisted around in pairs. Most of the world communication is built around this technology. There are the CAT 5 and the CAT 6 – which is more insulated for any interference. Transmission speed can go up to 100Mbps

•

Coaxial Cable – This wire consist of insulted copper, wrapped with solid or braided shield. It can have transmission speed up to 550Mbps.

It is very durable and be used for outside and even underwater

•

Fiber Optic Cable – consist of thousand of thin glass strands(human hair) from where light pass then electricity. Data is not effected by electricity interference. Speed is about 30 Gbps.

Wireless •

Infrared (IR) Channels – used electromagnetic spectrum. Used for short distance at 4Mbps. (home TV remote)

•

Bluetooth / Wi-Fi (wireless fidelity) – make use of high frequency radio wave technology. (mobile phone sharing) – about 10Mbps.

•

Terrestrial Microwave – involves high speed radio transmission sent through the planet atmosphere. It range is of 50Km and data transfer of 100Mbps.

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4. WHAT IS PROCESS CONTROL? In some case the computer does not only do INPUT – PROCESS – OUTPUT, but the OUTPUT is taken again by the computer as a new input. This is called PROCESS CONTROL.

[INPUT (DATA)] ===> [PROCESS] ===> [OUTPUT]

PROCESS CONTROL Example: The ABS System) of a car.

-

(Anti

Braking

where the output is taken again as input

If computer system is given the wrong data as input the computer in return will give the wrong information as output. This is called GIGO – Garbage IN Garbage OUT.

A computer is an electronic machine, which works under the control of a stored program, automatically accepting and processing data to produce information.

A program is a complete set of instructions, which instruct the computer to perform a particular task.

So the computer is an information-processing machine. It’s tasks are: handling information; inputting; processing; outputting; storing; retrieving; sending and receiving information.

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5. TYPES OF COMPUTERS: The two principal characteristics of a computer are: It responds to a specific set of instructions in a welldefined manner. It can execute a prerecorded list of instructions (a program).

Modern computers are electronic and digital.

The actual machinery - wires, transistors, and circuits -- is called hardware; the instructions and data are called software.

Computers can be divided into two categories: Computer: Designed to solve more than Home Personal

-

General Purpose one task – like Computer.

-

Special Purpose Computers: Designed to solve ONLY a particular task – like Autopilot or washing machine or play station which will have special input and output device.

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6. THE CPU The CPU is short for Central Processing Unit; this is the part of the computer where work gets done. In most computers, there is one processing chip. The CPU is the brains of the computer. Sometimes referred to simply as the processor or central processor, the CPU is where most calculations take place. In terms of computing power, the CPU is the most important element of a computer system.

The term processor has generally replaced the term central processing unit (CPU). The processor in a personal computer or that is embedded in small devices is often called a microprocessor. The CPU is that little device located on your motherboard that seems to be the heart of the system. Your CPU has several jobs but only one primary objective, that is take simple tasks and do them FAST!

CPU Control Unit Arithmetic Logic Unit

Input

data / information control lines

Memory

Output

Backing Storage

Three typical components of a CPU are:

ARITHMETIC AND LOGIC UNIT â&#x20AC;&#x201C; ALU: This is the part that executes the computer's commands. A command must be either a basic arithmetic operation: + - */ or one of the logical comparisons: > < = not =. Everything else has to be broken down into these few operations. Only one operation is done in each

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Machine Cycle. The ALU can only do one thing at a time but can work very, very fast. The ALU has two main registers; the accumulator and the shift register.

• The accumulator is used for storing the current result of a calculation.

•

The shift register is capable of shifting its contents one or more positions to the right or to the left, in order to carry out arithmetic operations. This shifting will result in a division by two when shifting to the left.

CONTROL UNIT - CU: It is a typical component of the CPU that implements the microprocessor instruction set. It extracts instructions from memory and decodes and executes them, and sends the necessary signals to the ALU to perform the operation needed. Control Units are either hardwired (instruction register is hardwired to rest of the microprocessor) or micro-programmed. Two registers which are found in the CU are the Instruction Register and the Program Counter.

• The Instruction Register stores a copy of the current instruction being processed.

•

The Program Counter stores the Address of the next instruction, in the program, to be executed

The MAIN MEMORY: It is divided into two parts; the RAM, short for Random Access Memory and ROM short for Read Only Memory.

•

The Random Access Memory is used for the temporary storage of data and programs. The time taken to fetch data is called the Access time. RAM is volatile, this means that everything stored in the RAM is lost when the computer is switched off. It is mainly for this reason that backing stores are an essential part of a computer system.

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•

The Read Only Memory is part of the central memory and is used to store data of a permanent nature. The information is normally put on a storage chip at the manufacturing stage.

The contents of ROM cannot be changed. ROM is used primarily for storing the Bootstrap Loader.

REGISTERS: There are 4 registers, the instruction register and the programme counter which are found in the control unit, the accumulator and shift register which are found in the arithmetic logic unit.

•

Instruction Register: stores a copy of the current instruction being processed.

•

Programme Counter: stores the address of the next instruction to the programme to be executed.

•

Accumulator: calculation.

•

Shift Register: is a cable of shifting its contents one or more positions to the right or to the left, in order to carry out arithmetic operations.

is used for storing the current result of the

Computer Speed: The first and most important is the speed with which the CPU chip can operate.

This depends on the internal clock of the CPU and is measured in MHz or MIPs (million of instructions per second).

MACHINE CODE It is the set of all possible instructions available from the electronic design of a particular computer. These instructions usually reflect the hardware design of the computer, and operate on very basic data, such as bytes or even single bits.

The instruction can only be understood by the computer when expressed in binary notation. A manufacturer designs a computer to obey just one language, its machine code, which will be represented inside the computer by combinations of binary digits. The set of binary codes which can be

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recognized by the computer is known as the machine code instruction set.

INSTRUCITON FORMAT The instruction format of a machine code instruction has two main parts: • •

A function (or operation) opcode; An address (operand).

e.g.

Op. code

Operand address

0 0 1 1

0 0 0 0 0 0 0 0 1 0

The function code tells the control unit of the CPU what to do with the item held in the address.

For example, for one computer: 4 A 2

187

Instruction (op. code)

Address

might be the hexadecimal machine code instruction for: ‘add the contents of storage location 187 to the contents of register 2’.

The absolute address of each store location is a binary number which can be decoded so that when data is required from a memory cell the right location is selected.

Opcode: It is short for operational code and is the mnemonic part of an instruction sort of the action to do part.

Operand: It is the mathematical part of the instruction – data upon which the op code is to carry out the action. (where to do action)

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7. THE FETCH AND EXECUTE CYCLE The fetch execute cycle is the time period of which the computer reads and processes the instructions from the memory, and executes them.

This process is a continuous cycle which is used until the computer is turned off or there are no more instructions to process.

FETCH The fetch part of the cycle starts by instructions being collected either from the hard-drive, the RAM, the cache or the registers. The way it knows which order to retrieve the instructions in is by each instruction being given a unique ID which are stored in a register so the control unit knows exactly what its looking for. (similar to how a computer has a unique IP Address on a network).

EXECUTE After the correct instructions have been fetched the CPU will then interpret what the instruction is telling it to do then it will simply execute the instruction and the whole process will begin again until there are no more instructions or the computer is turned off.

So the fetch-decode-execute is a repetitive process (steps) of fetching an instruction from main memory unit and executing it.

Step 1: Set the value of the Program Counter to the address of the 1st instruction.

Step 2: Fetch the instruction from the location specified by the Program Counter.

Step 3: Store a copy of this instruction in the Instruction Register.

Step 4: Increment the Program Counter by 1.

Step 5: Execute the instruction.

Step 6: Go back to Step 2 until the program ends.

Flow of Data inside the CPU

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8. IT PERSONEL ROLES Information Technology has many job components. An I.T. professional is an expert in one area, not all. It is impossible to master all the components since each component is so huge. Therefore to enter this profession you must choose an area of expertise for yourself that you wish to master. Information Technology has 4 major components: • Databases • Front-end tools • Networking • Operating Systems These components have given rise Information Technology: • Database Administrator • Application Developer • Applications Functional Expert • E-Commerce/Web Developer • Network Engineer • Operating System Administrator • Project Manager • And others as mentioned below

to

the

following

roles

I T MANAGER He is o o o

the man responsible for all the IT department.

Employ all workers at the IT section.

Ensure that computer department is running smoothly.

Create new opportunities for company to make more profit.

- SYSTEM DEVELOPMENT MANAGER He is the man responsible for the System Development Department. o Ensure that research and development are running smoothly. o Ensure deadline for new system implementation are reached. o Ensure project original guidelines are followed.

- DATABASE ADMINISTRATOR A Database Administrator is responsible for managing the database.. o Design Database to be used. o Test database.

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o Give right and access to whom have to access database o Do timetable of backup system o Label old file to any future reference - NETWORK ADMINISTRATOR The Network Administrator is responsible for managing the network o Create new profiles. o Check that system will not be overloaded. o Check all computer are connect to the internet. o Check for any viruses in employees emails. o Keep up to date with new technology.

- OPERATION MANAGER He is responsible for the data entry department. o Ensure that data entry is running smoothly o Train staff o Do problem solving meeting. o Do timetable for staff and resources

SYSTEM DEVELOPMENT MANAGER Project Manager is responsible for managing the I.T. project and bringing it to completion. This person possesses more soft skills than technical skills. This role requires skills of people management, resource planning, writing project plans, managing conflicts and managing time and activities of the team.

SYSTEM DESIGNER (ANALYST) o Define inputs & outputs of new system. o Do feasibility study. o Design program flowchart. o Write up documentation for new system.

SYSTEM PROGRAMMER o Write system (operating) software.

APPLICATION PROGRAMMER o Write application programs.

SENOIR PROGRAMMER o Develop program through a flowchart. o Take care of JUNIOR programmers. o Co ordinate Junior Programmer work.

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JUNIOR PROGRAMMER o Write programs source code. o Prepare INLINE documentation for future reference. o Test program by give data from Senior Programmer.

IT TRAINER o Train new employees on how to use system. o Coordinate courses with other departments. o Teach the NON-IT staff with new developed programs.

DATABASE MANAGER FILE LIBRARIAN o Responsible for all the safekeeping of Database files. o Do backup of files regularly. o Fetch for any deleted files that are deleted by mistake. o Reinstall any deleted files to the system.

NETWORK ADMINISTRATOR Network Engineer is responsible for maintaining the network in an organization. A network engineer is specialized in one of the networking technologies like NT, CISCO or Novell COMPUTER ENGINEER o Initially setting up the system. o Solve hardware problem not solved by technician. o Thinking of upgrading present system. o Check compatibility of current software with new system.

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COMPUTER TECHNICIAN o Repair faulty equipment. o Replaces faulty equipment. o Install new hardware to the system. o Maintains ‘older’ hardware in working order.

OPERATION MANAGER Operating system administrator's role is very similar to that of a database administrator. Operating system administrator manages the health of the operating system. Managing directories, managing operating system security, creating backup and restoring them, installing products are all part of his duties. This role involves working closely with database administrators (DBAs) and application developers. This role also requires basic programming skills.

Sometimes operating system administrators have to write small programs to automate certain processes.

COMPUTER OPERATOR o Ensure input and output media are ready (printers…) . o Power up computer and machines. o Record any errors in error log book. o Clean devices from dust. o Regulate computer environment room temperature. o Delete unwanted files and directories DATA ENTRY CLERK o Enter data into the computer. (Typists). o Check the date inputted is correct. o Correct an incorrect data when found.

WEB MASTER o Creates and host the company web page. o Maintains and update the web page o He act as a link between the client (problem) and programmer (have solution) o Do all internet links for the company. o Display all new products and achievements of the company.

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9. FILING SYSTEM SEQUENTIAL FILE: Sometimes called: serial file: is a file in which the records are stored in a specified order. For example, in record system this could be in alphabetic order of the surname or in n order of reference number.

RANDOM ACCESS FILE is a file where the records are stored sequentially, that is one after another, but can be directly accessed, as in a random file. This is done by u position of the data in the file as its address.

RECORD NUMBER is a unique number which identifies the position of a record in a data means that record number one identifies the first physical position and in that position. The concept of a record number is not used in some file structures such as random files and in some relational database system.

Many data files can be processed serially by working through the file on at a time and, in this situation, the record number identifies the position of the record currently being processed. A record number may serve as a pointer.

ARCHIVE FILE is one containing data no longer in use, but held for historical purposes, perhaps for auditors. It is often stored away from the computer system, in a secure location.

BACKUP FILE is a copy of a current file kept as a security measure in case the original is corrupted in any way. As with an archive file it is often kept in secure location away from the computer system.

REFERENCE FILE is a special type of master file which is not updated during the job being processed. It contains fixed data that does not change. When changes are necessary, this will be achieved by a separate program.

MASTER FILE Including: transaction file is the principal source of data for an application. It holds data which is mostly static but which can be added to or amended by updating as necessary during processing. In a traditional commercial batch-processing application, such as a payroll,

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the master file (of all employees) is updated by reference to a transaction file of hours worked in the current month, leave, sickness, promotions, etc.

GRANDFATHER, FATHER, SON - BACKUP FILES Grandfather, father & son are the three most recent versions of a file that is periodically updated, for example the master file in a batchprocessing application such as a payroll. The most recent, the ‘son’ file, is used for the next run of the program; if an error occurs that corrupts this copy of the master file, the ‘father’ version is still available, and can be used with an archive copy of the transaction file from the previous run, to re-create the damaged ‘son’ version. The ‘grandfather’ version provides an additional level of security.

The file generation starts from the transaction file, which then leads to the reproduction of a master file. When a new master file is then created the old master file is called the father and now the new master file is called the son. This is a process that can be repeated more than once.

For example: The newest master file becomes the son, the master file that was used to produce it becomes the father, and the original master file becomes the grandfather. All these files put together (grandfather, father, son) make the file generation.☺. The more files there are the update there is. These kinds of files are always awaiting some kind of action.

INDEX FILE: is a file used to access a large data file quickly. It contains key field data from the file that the index is for. The key data is in a format which can be searched quickly and the attached addresses are used to access the data.

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DATA PROTECTION ACT: The Data Protection Act 1998 is a United Kingdom Act of Parliament which defines UK law on the processing of data on identifiable living people. In practice it provides a way for individuals to control information about themselves. Anyone holding personal data for other purposes is legally obliged to comply with this Act. This law which start that certain data with is sensitive stored on computer must be protected by passwords so that unauthorized users will not access it or pas it to others without the consensus of the owner.

Data Controllers are persons who check that this law is obey and no data is stolen!!! What must be done on stored data: o o o o o

Delete old and unwanted file Update frequently so data will be up to date Create passwords so data will be secure Do and protect backup of data.

Before publishing any data – owner must give you go ahead!!

DATA SECURITY: It is when you protect your data stored on the computer. It is done: • • •

by backup o (so no data is lost if something happens) by passwords o (so no data is stolen by unauthorized users) old data deleted o especial after updates or very old data

DATA INTEGRITY: It is when data inputted into the computer is 100% correct. This is done by the • • • •

Data preparation form o printed filled form MUST look like input screen Visual Check o after typing check with eyes Verification o typing x2 times by two different persons & compare Validation o different types of checking – type, range, etc

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10. COMPUTERS AT WORK WHERE COMPUTERS MIGHT BE MORE APPROPRIATE THAN PEOPLE • • • •

Repetitive tasks Easily automated tasks Mathematical calculations Dangerous situations

WHERE PEOPLE MIGHT BE MORE APPROPRIATE THAN COMPUTERS •

•

•

Computers have their limits. When you are unwell and visit your doctor, it is often a person to whom you want to talk. The human touch is important.

Computers are very bad at recognising and interpreting shapes.

They can take photographs and record images on video, but they have no understanding of the meaning of shapes, and will be easily confused when presented with two overlapping shapes.

In time things may change, it was not very long ago that a computer was incapable of beating a chess grand master.

COMPUTER APPLICATIONS IN BUSINESS • •

•

•

Business administration systems: The classic use of a computer is to run business administration systems, and all aspects of this have now been computerised.

Airline booking systems: Airline booking systems have long been computerised. This maximises profit for the airline companies and is often more convenience for the customer. Many of these airlinebooking systems have now also been integrated with online airline ticket sales.

Insurance claims processing: All insurance companies use very large mainframe computers, combined with specialist software to manage their business. The software involved can handle all aspects of claims procedures.

Online banking: Most banks now offer some form of online banking. This has the advantage to the bank that costs can be reduced. Some banks are completely online, with no physical branches at all. The customers benefit from 24-hour access to banking services. The downside is that this leads too many job losses in the banking industry and when things go wrong there is no physical person you can go and see and make your complaints to.

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COMPUTERS APPLICATIONS WITHIN GOVERNMENT • • • •

Census: Every few years census details are taken and entered into large computer databases. This data can then be used to extract useful information and predict trends.

Vehicle registration: All car and lorry details are kept centrally; this makes it easy to find the owners of cars, which can be useful for police, customs and security services.

Revenue collection: Increasingly aspects of government revenue collection are being computerised, which in many cases involves online systems as well.

Electronic voting: Governments are experimenting with online voting systems, often in response to low voter turnout. Security remains the main obstacle.

COMPUTER APPLICATIONS IN HOSPITALS AND HEALTH CARE

• • •

Patient record systems: Appointment and record systems are computerised and centralised.

Ambulance control systems: Ambulances are often centrally controlled and the computer systems can now integrate satellite positioning to pinpoint the location of each ambulance.

Diagnostic tools and specialist surgical equipment: The modern intensive care facility is filled with computerised diagnostic equipment: monitor heart rate, blood pressure etc.

COMPUTER APPLICATIONS IN EDUCATION

• •

•

•

Student registration and timetabling: These are programs designed to computerise school registration and do timetables.

Computer Based Training (CBT): Computer Based Training (CBT) offers a low cost solution to training needs where you need to train a large amount of people on a single subject. As an alternative to training via CD/DVD, CBT can also be delivered via the Internet.

Using the Internet as a homework resource: The Internet is the ultimate resource for getting the information necessary to complete a student’s homework. The Internet can also be used to set and collect homework (via email).

Distance learning systems: E-learning is a term used to describe studying via the Internet. It can take many forms ranging from a simple web version of printed books, through to advanced use of video images with sound. In many cases there can be real-time two-way communication between the teacher and the student.

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Advantages include: - One trainer can train many people at many different locations.

- If the training is solely computer based, then the students can work at their own pace, and repeat parts of a course which they do not understand. Also the teaching can be at any time, 24 hours a day, 7 days a week.

- Often e-learning solutions are cheaper to provide.

Disadvantages include: - There may be no opportunity to ask a question of a real person.

- The Internet connection may temporarily fail for some reason.

- You may have to pay for the connection time, by the minute.

- The download speed may be too slow for some forms of e-learning - Because of the increased time required to produce some types of elearning packages, the e-learning tutorials may not be available for some time following the release of a new version of software, or a new certification syllabus.

OTHER COMPUTER APPLICATIONS & USE Computer Process Control: A digital computer is used to direct the operations of a manufacturing process. Includes the measurement of important variables (eg: temperature), execution of some optimizing strategy, actuation of such devices as valves and switches, and generation of reports.

Robotics: A robot is a system with a mechanical body using computer as its brain. Integrating the sensors and actuators built into the mechanical body, the motions are realized with the computer software to execute the desired tasks.

Gas and Oil Exploration: Finding the right conditions for an oil trap, the right source rock, reservoir rock and entrapment. Tiny changes in the Earth's gravitational field that could indicate flowing oil can be measured.

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Banks: Bank accounts are accessed through phone lines, ATMs and the Internet. A single plastic card and bank code will allow you access to your bank account 24 hours a day. Banks use computers to work out the interest on loans and saving accounts, keep track of how much money a bank is able to lend, compute how much money a bank may have at any given moment.

Stock Control: This is the term used in business to denote the levels of stock a business has in its stores. The Stock Control software stores and maintains stock levels for the user and informs him/her when the stock of a particular product is low.

E-Commerce: Electronic commerce is the idea of doing business electronically over the Internet. You select the items you wish to purchase and put them in your shopping cart. Then you are usually given the option to pay by cash, check or credit card.

Air Traffic Control: A system by which airplanes are safely routed into and out of major airports, along established airways to airport traffic control centers.

Space Travel: Computers have been used to keep the ships on course, plan their landing, and determine how long the return flight would take and how much fuel and oxygen would be used.

Intelligent Cars: Collision-avoidance will be advance enough to totally drive a car without any driver assistance. The only thing the automobile operator will need to do is enter a destination.

Police: With the installation of laptop computers in police cruisers, police officers can submit reports and gather information from their cars, without having to come to the station.

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Hospitals: When an alarm rings at the nurse's station the computer screen shows instantly that a patient is in trouble. Electronic sensors are taped to the patient's chest, attached to a computer which can signal an irregular heartbeat.

Schools: Using Computer Assisted Instruction (CAI), to assist in learning. More and more classrooms and libraries are being connected to the Internet, where there is a large volume of information to be gathered and where tutorials, quizzes and lessons are available.

Tele shopping: The use of telecommunications and computers to shop for and purchase goods and services.

WHAT IS TELE-WORKING? Tele-working is a broad term which refers to people working at home connected to the rest of the organisation via a computer network.

Some of the advantages of Tele-working - Reduced or zero commuting time - Greater ability to focus on one task - Flexible schedules - Reduced office desk space requirements Some of the disadvantages of Tele-working - Lack of human contact - Negative impact on teamwork - Self-discipline - Possible Employee Exploitation

What is email?

Email allows you to send a message to another person almost instantly, anywhere in the world. It requires both computers to be connected to the Internet. As well as sending a text message, files can be sent as email attachments.

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What is E-commerce?

You can purchase directly via a Web site by selecting the goods or services which you require and entering your credit card details. When you send your credit card details these SHOULD be encrypted by the site operators so that no one can intercept your details.

What is E-banking?

The phrase e-banking relates to managing your money online. Instead of having to go to the local branch, or telephoning them, you can pay your bills online and move money from one place to another. Some online banks have no physical branches at all, making it a very profitable operation for the bank. There are security considerations relating to online banking, with numerous examples of poor security.

The process of shopping online There are numerous web sites from where you can purchase online, the most famous of all being amazon.com as illustrated. Most Internet based shopping sites use a virtual â&#x20AC;&#x153;shopping cartâ&#x20AC;? system. As you browse the site you can add any products you want to purchase to your cart.

The advantages of e-commerce - Services available 24 / 7 - Large stock range - Detailed product information - Ability to compare prices - Equal delivery to town and country - Right to return defective goods The disadvantages of e-commerce - Possible Credit card Fraud - Is the web site genuine - What about returning faulty goods - Are covered when you purchase goods from another country?

- Can you talk to a real person

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11. MULTIMEDIA Multimedia is the use of technology to better communicate information. This includes the use of digital video, interactive programs, Internet content, graphics, audio, 3-D animation, 2-D illustration and any other computer-delivered media. An electronic encyclopedia is an example of a multimedia application. Multimedia is and will be more introduced in almost every aspect of society such as houses, offices (presentations), libraries, films, etc. In fact, Multimedia Messaging Service (MMS) is a new standard in mobile messaging. Like SMS (Short Messaging Service), MMS is a way to send a message from one mobile to another. The difference is that MMS can include not just text, but also sound, images and video. It is also possible to send MMS messages from a mobile phone to an email address.

Multimedia helps demonstrate subjects that require time, movement etc. to understand. It also supports different learning styles and adds interest to the learning materials. It highly supports those with special needs.

So multimedia is the use of computers to present text, graphics, video, animation, and sound in an integrated way.

Text: Words, sentences, paragraphs. This book, for example, consists of text. Text processing refers to the ability to manipulate words, lines, and pages. Typically, the term text refers to text stored as ASCII codes (that is, without any formatting). Objects that are not text include graphics, numbers (if they're not stored as ASCII characters), and program code.

Graphics: Refers to any computer device or program that makes a computer capable of displaying and manipulating pictures. The term also refers to the images themselves. For example, laser printers and plotters are graphics devices because they permit the computer to output pictures. A graphics monitor is a display monitor that can display pictures. A graphics board (or graphics card) is a printed circuit board that, when installed in a computer, permits the computer to display pictures Video: Refers to recording, manipulating, and displaying moving images, especially in a format that can be presented on a television.

Another example is the displaying images and text on a computer monitor. The video adapter, for example, is responsible for sending

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signals to the display device. A recording produced with a video recorder (camcorder) or some other device that captures full motion.

Animation: A simulation of movement created by displaying a series of pictures, or frames. Cartoons on television is one example of animation. Animation on computers is one of the chief ingredients of multimedia presentations. There are many software applications that enable you to create animations that you can display on a computer monitor.

Note the difference between animation and video. Whereas video takes continuous motion and breaks it up into discrete frames, animation starts with independent pictures and puts them together to form the illusion of continuous motion.

Long touted as the future revolution in computing, multimedia applications were, until the mid-90s, uncommon due to the expensive hardware required. With increases in performance and decreases in price, however, multimedia is now commonplace. Nearly all PCs are capable of displaying video, though the resolution available depends on the power of the computer's video adapter and CPU. So Multimedia is the integration of TEXT, GRAPHICS, VIDEO, ANIMATION and SOUND integrated together as on thing. So a multimedia program, is a program were you will find sound, good graphics, text and animation mixed together. Nowadays nearly all programs and games are being designed as multimedia â&#x20AC;&#x201C; more beautiful and more user friendly. Even the computer must have larger memories and good graphics installed in order to run these programs.

CLI vs GUI COMMAND LINE INTERFACE: Short for command line interface, a user interface common to MS-DOS computers. The user sees the command line on the monitor and a prompt that is waiting to accept instructions from the user. The user types in the command, the computer acts on that command and then issues a new prompt for the next

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instruction from the user.

CLI operating systems are becoming less used as GUI operating systems gain in popularity. In a GUI operating system, such as Windows, the user responds to graphic images on the screen instead of typing in commands in response to a prompt GRAPHICAL USER INTERFACE: A program interface that takes advantage of the computer's graphics capabilities to make the program easier to use. Well-designed graphical user interfaces can free the user from learning complex command languages. On the other hand, many users find that they work more effectively with a command-driven interface, especially if they already know the command language.

Graphical user interfaces program, such as Microsoft Windows and the one used by the Apple Macintosh, feature the following basic components: Pointer : A symbol that appears on the display screen and that you move to select objects and commands.

Pointing device : A device, such as a mouse or trackball, that enables you to select objects on the display screen.

Icons: Small pictures that represent commands, files, or windows. By moving the pointer to the icon and pressing a mouse button, you can execute a command or convert the icon into a window.

Desktop : The area on the display screen where icons are grouped is often referred to as the desktop because the icons are intended to represent real objects on a real desktop.

Windows: You can divide the screen into different areas. In each window, different program by run or display.

Menus: Most graphical user interfaces let you execute commands by selecting a choice from a menu.

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12. ABBREVIATIONS & TERMINOLOGY Item ADSL Bit Bps Byte CAD CAL CAM CBT CD CD-R CD-ROM CLI CPS CPU DAT DOS DSL DTP DVD FTP GIGO GByte GHz GUI HTTP Hz IP IS ISDN IT KByte LAN MByte MAN MHz PC PPM POS PSTN RAM ROM ROM-BIOS

Meaning Asymmetric Digital Subscriber Line 1 or 0 level of storage is called a bit Bits Per Second A measurement of storage capacity Computer Aided Design Computer Aided Learning Computer Aided Machine Computer Based Training Compact Disk Compact Disk - Recordable Compact Disk - Read Only Memory Command Line Interface Character per Second Central Processing Unit Digital Audio Tape Disk Operating System Digital Subscriber Lines Desk Top Publisher Digital Versatile Disk File Transfer Protocol Garbage In Garbage Out Gigabyte. A gigabyte consists of 1024 MBytes Measurement of computer speed. Gigahertz Graphical User Interface HyperText Transfer Protocol Hertz ( this is a measurement of frequency (i.e. speed).

Internet Protoct Information Systems Integrated Services Digital Network Information Technology Kilobyte. A kilobyte (KB) consists of 1024 bytes.

Local Area Network Megabyte. A megabyte (MB) is one million bytes Metropolitan Area Network Million Hertz Personal Computer Page per Minute Point of Sale Public Switched Telephone Network Random Access Memory Read Only Memory Read Only Memory - Basic Input Output System

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RSI TFT TByte UPS USB VDU WAN WWW

Repetitive Strain Injury Thin Film Transistor Terabyte. A terabyte (TB) is one million Mbytes Uninterruptible Power Supply Universal Serial Bus Visual Display Unit Wide Area Network World Wide Web

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