A computer is a high-speed electronic device that accepts data and instructions from the user, then processes the data accordingly to produce information as output. It is capable of performing arithmetic and logical operations on data. It also stores and executes set of instructions. Data is entered in the computer through some input devices like keyboard, mouse, etc. It is then processed by C.P.U. and the result is displayed through an output device like a monitor.

The invention of the computer has affected many areas of our life. In its early time, it was a very costly and rare machine, limited to scientific laboratories and research centres. It was difficult to work on  and they were very bulky. Slowly, the technology improved and the size of the computer reduced as well as its working became easy.

Computers have completely altered the structure of a business, a large volume of accounting and record-keeping, data can be manipulated, organized, stored, retrieved and used for scientific purposes.

Nowadays, a computer is used in homes, offices, shops and almost every-where. It is used to do simple as well as the most difficult calculations. Every business, no matter big or small, is based on computers. Similarly, an organization without computer is hard to find. Computer has changed the world.

Evolution of Computer: The first mechanical calculator developed by Blaise Pascal acted as a model for modem computers. Since then many machines have been developed which have to lead the way to modem microcomputers. A series of a scientific breakthrough by many scientists have contributed to produce this electronic machine called the computer.

1. Abacus: Movable beads on a wooden frame constituted the first  known calculating device. The abacus was used by the ancient Greeks and Romans. 

2. Pascaline: The gear-driven machine capable of addition, subtraction and multiplication, considered as a first mechanical calculator, was invented by French mathematician Blaise Pascal in the year 1642.

3. Jacquard’s Loom: In 1801, a Frenchman named Joseph Jacquard perfected a loom that was controlled by the holes in cardboard punched cards. This machine gave an idea about storage.

4. Difference Engine: In 1822, Charles Babbage invented his first machine (Difference Engine). He designed it to calculate logarithm tables. A series of levers were used to enter the data and a device similar to the typewriter was used to print the output.

5. Analytical Engine: In 1833, it was developed by Charles Babbage to perform addition, subtraction, multiplication and division through the use of the stored program. First programmer lady Ada Augusta Byron Lovelace helped him in its developing.

6. Atanasoff-Berry Computer: This electronic machine was developed by Dr John Atanasoff in 1939 for certain mathematical equations. It was called Atanasoff-Berry Computer or ABC, after its inventor’s name and his assistant Clifford Berry. It used 45 vacuum tubes for internal logic and capacitors for storage.

7. Mark 1: In 1944, Dr. Howard Aiken developed a machine called an  Automatic Sequence Controlled Calculator which was later named as Mark-I. It was the first electromechanical computer.

Age Difference Calculator helps to determine the age gap between two persons easily.

8. ENIAC: First fully electronic computer named ENIAC (Electronic Numerical Integrator and Calculator) was developed by Prosper Eckert and J.W. Mauchly in 1945. It used highspeed vacuum tube switching devices.

9. EDVAC: In 1946, Dr John Von Neumann used the principle of storing in 0 and 1 (Binary Digits) in place of earlier technologies and developed EDVAC with the new concept of ‘stored program’. ED VAC (Electronic Discrete Variable Automatic Computer).

10. UNIVAC: Universal Automatic Computer was developed by Eckert and Mauchly in the year 1951. It was the first commercial computer used by Electronic Corporation. Its memory was MDL (Mercury Delay Line).

11. PDP Series: The computer of this series was developed by DEC (Digital Equipment Corporation)

.  PDP-1 → 1961 → 8 bit → 4 KB 

.  PDP-8 → 1965 → 16 bit → 16 KB 

.  PDP-11 → 1970 → 16 bit → 32 KB

12. Micro Computers: Intel is the No. 1 company in the microprocessor. The microprocessors developed by this company were the best for microcomputers, few of them are as follows:

8080 → 1974 → 8 bits

8085 → 1978 → 8 bits

8086 → 1980 → 16 bits

80286 → 1982 → 32 bits

80386 → 1985 → 32 bits

80486 → 1986 → 32 bits

13. Pentium Series: After 80486, Intel developed Pentium processors which are used almost in every computer nowadays.

Pentium → 1993

Pentium I → 1995

Pentium II → 1997

Pentium Mobile → 1998

Pentium III → 1999

Pentium IV → 2000

Pentium Centrino → 2004