The word computer comes from the word “compute”, which means, “to calculate”. Thereby, a computer is an electronic device that can perform arithmetic operations at high speed. A computer is also called a data processor because it can store,process, and retrieve data whenever desired.

There are many kinds of characteristics of computers. Given a job, computer can work on it automatically without human interventions.

Computer can perform data processing jobs very fast, usually measured in microseconds (10-6), nanoseconds (10-9), and picoseconds (10-12).

Accuracy of a computer is consistently high and the degree of its accuracy depends upon its design. Computer errors caused due to incorrect input data or unreliable programs are often referred to as Garbage-In-Garbage-Out (GIGO).
Computer is free from monotony, tiredness, and lack of concentration. It can continuously work for hours without creating any error and without grumbling.

Computers are devoid of emotions. Their judgment is based on the instructions given to them in the form of programs that are written by us (human beings).
The abacus is a manually operated digital computer used in ancient civilizations. The use of the word abacus dates before 1387 AD. The first mechanical adding machine (calculator) was invented by Blaise Pascal (French) in 1642.

Baron Gottfried Wilhelm von Leibniz invented the first calculator for multiplication in 1671.

Keyboard machines originated in the United States around 1880.

Around 1880, Herman Hollerith came up with the concept of punched cards that were extensively used as input media until late 1970s.

Charles Babbage is considered to be the father of modern digital computers. He is best remembered now for originating the concept of a programmable computer. He designed “Difference Engine” in 1822. He designed a fully automatic analytical engine in 1842 for performing basic arithmetic functions. His efforts established a number of principles that are fundamental to the design of any digital computer.