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Cit Notes for Reference

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Cit Notes for Reference

Page 1 of 110
computer science

1. I/O Devices1
2. Memory19
3. Central Processing Unit47
4. PC Hardware59
5. Database Concepts75
6. Review of C++90
7. Object Oriented Programming109
8. Polymorphism136
9. Inheritance144
10. Files167


Data are entered in to the computer system by means of an input device. The keyboard is one of the most commonly used input device. Other common one included are MICR, OCR, OMR, Digitizer, Joystick, trackball, light pen, mouse etc. There are also unusual input devices that respond to voice and touch. On touch sensitive screens, the user simply touches the location on the screen, where the description of the desired operation is displayed. The computer senses where the screen has been touched and performs the indicated operation.

The following are some functions performed by the input unit.

1. It accepts the list of instructions and data performed by the input unit. 2. It converts these instructions and data from the outside world. 3. It supplies the converted instructions and data to the computer system for further processing.

Key Board

It is the most common and familiar input device used. A keyboard typically has characters printed on the keys and each press of a key typically corresponds to a single written symbol. When a user presses a key, electric signals must be generated which will enable the computer (or other device) the switch in the housing are closed, and the two terminals at the output are effectively connected When the plunger is up( i.e., when the key is not pressed) the switch in the housing is open , and the terminals are not electrically connected. The most popular keyboard used today is the 101 keys QWERTY keyboard.

Keys in keyboard

To determine which key is pressed. This is called...