Introduction:

Computer is an electronic machine and a mechanical device which can store, retrieve and manipulate the 'data' with high speed and accuracy according to a list of instructions called 'programmes'.
It is a device that processes the data. Due to technological advancement, modern electronic computers are exponentially more capable than those of preceding generations. However, it does the following function during data processing.
(i) It accepts the data from the users called 'input'.
(ii) It accepts instructions from the users input'.
(iii) It converts the data into information 'processing'.
(iv) It displays the results as 'output'.
It means that a computer performs all the work in an integrated way.
Input Unit ->Processing Unit -> Output Unit

Origin of Computer:

Charles Babbage developed the first analytical engine in 1812. This machine had the concepts of modern computers namely memory, arithmetic unit and capacity to handle stored program. But this machine could not be put into practical applications due to technological limitations tat that time.

Classification of Computers:
There are different types of inputs that computers accept. On this basis, computers can be classified into three types: analog computer, digital computer and hybrid computer.