Information technology is a technology that merges computers and high speed communication links, carrying data, sounds and video.

Information technology made of two things computers and communication links. In other words we also can say that it is the combination of computers and speedy links of communications.

 DEFINITION OF A COMPUTER

In Pakistan, computerization process geared up in 1983-84. When government of Pakistan lifted ban on the import of computer and waived all the import duties. By virtue of this liberal import policy. Pakistan could enter in the revolution of personal computers (PC) making computation so economical that many people can now easily afford their own personal computers.

            A computer can be defined as,

(1)   “A device that accepts input of information or data, process the data according to prescribed steps of instructions and supplies the output”.

(2)   “ A device capable performing computations and making logical decisions at speeds thousands and even millions of times faster that human beings” The dictionary define computer as ,

(3)   “An electronic device that stores retrieves and process information” Computer is extremely efficient and reliable machine It has the advantage over human mind, that it does not get bored of repetition and performs a function each time with the same speed and accuracy.

A modern computer is a highly complete electronic machine, capable of performing a million distinct operations a reword with accuracy and reliability.

FUNCTIONAL ORGANIZATION OR COMPONENTS OF A COMPUTER

            A digital computer consists of several components, each containing mechanical and electrical equipments. There are three basic components of a computer.

THE ARCHITECTURE OF A COMPUTER

            Memory (primary storage) arithmetic and logic unit (ALU) and control unit comprise the cpu. The following figure is a slightly more detailed version of the above.

ORGANIZATION OF COMPUTER SYSTEM

 1.            Input Unit:

             The receiving section of the computer system is called input unit this section provider data or information to CPU. The early computer system used punched cards and punched paper tapes for data entry. Now a days keyboard is the standard source for this purpose. There are other input devices such as mouse, joysticks, touch screens, scanner etc.

 2.            CPU:

                    It stands for central processing unit. This is the administrative section of the computer. The CPU is connected to all input and output devices, storage unit and all other parts of the computer system. The CPU is collection of three units.

MEMORY

·        ALU

·        CONTROL UNIT

                         MEMORY:

           This is the “warehouse” Section of the computer. In this unit program and their data are stored. This unit is after called either main storage internal storage, primary storage or simply memory. There are usually two types of this section.

 1.                 RAM

                     Random Access Memory is the memory whose information can be erased or changed this portion of  memory store data temporary. So it is called volatile memory.

           2.                 ROM

                     It stands for Read Only Memory. The information can only be read from ROM not written to it. It is  non-volatile memory. It can not be lost if you turn off the power to the computer. So ROM is used to store permanent programs.

            Other types of this memory are!

            PROM             Programmable Read Only Memory.

            EAROM            Electrically Alterable Rom.

            EPROM            Erasable Programmable Rom.

           ALU:

                 This is the calculating section of the computer. This is that part of CPU where all mathematical and logical functions are performed. By mathematical functions we mean addition, subtraction division, multiplication and all other mathematical functions. A logic function is one where numbers or conditions are compared to each other. e.g  greater than, less than, equal to etc.

         3.                 OUTPUT UNIT:

                 The equipments through which the processed information comes to the outside world is called output devices. e.g Monitors, Printers, Plotters, Speakers  etc.

             TYPES OF COMPUTERS

             The computers are classified on the basis of following heads.

             According to functions.

1.      Analog computers.

2.      Digital computers.

3.      Hybrid computers.

According to purpose.

1.      Special purpose computers.

2.      General purpose computers.

According to Size and capacity.

1.      Micro controllers.

2.      Supper computers.

3.      Main Frame computers.

4.      Mini Frame computers.

5.      Micro computers.

            HARD WARE AND SOFT WARE

            Hard Ware :

When we are talking about the computers. The words Hard Ware and Soft Ware are commonly used. The electronic and mechanical components of a computer system in fact these are the physical components and can be touched, handled or seen physically. These devices include input devices  i.e  Key Board, Mouse, Disk Drives  etc, central processing unit any extra storage and the output devices  i.e  Printers, Monitors  etc.

           Soft Ware :

Computer Hard Ware will do nothing until we tell it what to do. It is the Soft Ware that brings the Hard Ware to file Soft Ware is the name given to the actual programs. That allow the Hard Ware to do a useful job. With out Soft Ware, Hard Ware is quite useless. In fact it is the Soft Ware that tells the computer what to do and how to do.

          HISTORY OF COMPUTERS

The history of computer is very old initially computer was developed as an accounting machine. Drastic changes in this machine made it most effective and become a revolutionary invention of his century. The history of computers can be categorized into three ages.

1. Dark age                   (5000Bc – 1890 AD)

2. Middle age              (1890 AD – 1944 AD)

            3. Modern age             (Since 1944 AD)

·        Dark age:

Usually in this are (time) manual mechanical devices were used. The most effective inventions are given below.

1.                  Abacus (5000 Bc)

Probably developed in china, the abacus is a frame with beads strung on rods.

 Arithmetic calculations were performed by manipulating the beads.

                          2.            Napiers bones (1617)

      John Napier, a Scottish mathematician developed this device. Napier’s bones are a set of

     Cloven rods with numbers on them in such a way that by simply placing the rode side by

             Side additions and subtractions can obtained.

·        Middle age:

The middle ages of data processing are said to have begun when Dr. Heramn Hollerith, a statistician with the US. Bureau of the census, developed the first Electro mechanical punched card tabulator, which was driven by electricity and could sort and select data. This invention opened a gate to modern data processing and Hollerith went on to find the tabulation Machine company, which later be came IBM. His successor at the census bureau Dr. James Powers, also left to form his own company which ultimately became Sperry Rand corporation.

·        Modern age:

        Mark I  (1944)  Major innovation: The first computer capable of automatically performing a long sequence of arithmetic and logical operations. H. Aiken, Harward university, USA develop Mark I , a  first digital computer. It was an electromechanical machine that advanced  computer  technology by employing relays instead of gears.