In principle, a computer of any kind works in much the same way as a teacher. It is concerned with accepting data as input, storing all the information, which is relevant to it, processing the data in a pre-determined way that confirms with a program of instructions and then communicating the results as output. Thus a computer essentially consists of three elements.
1. Input Device
2. Central Processing Unit CPU
3. Out Device
Input and output devices provide, man to machine and machine to man communication and since, they surround CPU, and they are also called peripheral devices.
Input devices are of many types but basically they are meant for presenting the information of computer in machine readable form. A computer system may have one or more of following input device depending upon its type, size and use.
1. Punch Card Reader
2. Punched Paper Tape Reader
3. Magnetic Tape
4. Magnetic Disk
5. Floppy Disk
6. Teleprocessing Terminal Teletype Writer Terminal
7. Optical Scanner
(a) Optical Mark Reader;
(b) Optical Character Reader (OCR)
8. Magnetic Ink Character Reader (M.I.C.R.)
9. Visual Display Unit (VDU)
10. Voice Data Entry Terminal (V.D.E.)
Digitizer Graphics Tablet
Optical Bar Reader