Input And Output Devices Of A Computer

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Input and Output Devices

The terms “input” and “output” are used both as:
verbs to describe the process of entering /displaying the data. nouns referring to the data itself entered into /displayed by the computer.

Input Devices

Input devices are necessary to convert information or data in to a form which can be understood by the computer. A good input device should provide timely, accurate and useful data to the main memory of the computer for processing.


Keyboard is the standard input device attached to all computers. The layout of a keyboard is just like the traditional typewriter of the type QWERTY. It also contains some extra command keys and function keys. It contains a total of 101 to 104 keys.

You have to press correct combination of keys to input data. The computer can recognize the electrical signals corresponding to the correct key combination and processing is done accordingly. The computer keyboard is used to enter text information into the computer. The keyboard can also be used to type commands directing the computer to perform certain actions. Commands are typically chosen from an on-screen menu using a mouse, but there are often keyboard shortcuts for giving these same commands. keyboards usually have a numeric keypad, a bank of editing keys, and a row of function keys along the top. Laptop computers don’t have room for large keyboards.

they include a “fn” key so that other keys can perform double duty. Most keyboards attach to the PC via a PS/2 connector or USB port.

Pointing Devices

The graphical user interfaces (GUIs) in use today requires some kind of device for positioning the on-screen cursor. Typical pointing devices are:
touch pad,
graphics tablet,
touch screen.
Pointing devices are connected to a PC via a serial ports (old), PS/2 mouse port (newer), or USB port (newest).


A mouse is an input device that is used on personal computer. It rolls on a small ball and has two or three buttons on the top. When rolled across a flat surface the screen censors the mouse moves in the direction of mouse movement. In older mice, a ball in the bottom of the mouse rolls on the surface as it moves. internal rollers sense the ball movement and transmit the information to the computer via the cord of the mouse. The newer optical mouse uses a light and a small optical sensor to detect the motion of the mouse by tracking a tiny image of the desk surface. Optical mice avoid the problem of dirty mouse ball, which causes regular mice to roll unsmooth. A cordless or wireless mouse communicates with the computer via radio waves. such mice need internal batteries.

A mouse also includes one or more buttons (and possibly a scroll wheel) to allow users to interact with the GUI. The traditional PC mouse has two buttons, while the traditional Macintosh mouse has one button. On either type of computer you can also use mice with three or more buttons and a small scroll wheel.

Touch pad

Most laptop computers have a touch pad pointing device.
Moving the on-screen cursor is done by sliding a finger along the surface of the touch pad. The buttons are located below the pad, but most touch pads allow you to perform “mouse clicks” by tapping on the pad itself. Touch pads have the advantage over mice that they take up much less room to use. They have the advantage over trackballs that there are no moving parts to get dirty and result in jumpy cursor control.


Some sub-notebook computers, which lack room for even a touch pad, incorporate a trackpoint. a small rubber projection embedded between the keys of the keyboard. The trackpoint acts like a little joystick that can be used to control the position of the on-screen cursor.


Trackball is sort of like an upside-down mouse, with the ball located on top. A is fingers is used to roll the trackball, and internal rollers...
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