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Tuesday, October 26, 2010

Input-Output Devices

A computer is only useful when it is able to communicate with the external environment. When you work with the computer you feed your data and instructions through some devices to the computer. These devices are called Input devices. Similarly the computer after processing, gives output through other devices called output devices.
Common input and output devices are: Speakers, Mouse, Scanner, Printer,Joystick, CD-ROM, Keyboard, Microphone, DVD, Floppy drive, Hard drive, Magnetic tape, and Monitor. Some devices are capable of both input and output.
Figure 4: Typical input- output devices
Figure 4 (graphics4.png)
Input Devices
Input devices are necessary to convert our 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 followings are the most useful input devices.
Keyboard: - This is the standard input device attached to all computers. The layout of keyboard is just like the traditional typewriter. It also contains some extra command keys and function keys. It contains a total of 101 to 104 keys. You must 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.
Mouse: - Mouse is an input device that is used with your personal computer. It rolls on a small ball and has two or three buttons on the top.When you roll the mouse across a flat surface the screen censors the mouse in the direction of mouse movement. The cursor moves very fast with mouse giving you more freedom to work in any direction. It is easier and faster to move through a mouse.
Scanner: The keyboard can input only text through keys provided in it. If we want to input a picture the keyboard cannot do that. Scanner is an optical device that can input any graphical matter and display it back.
Output Devices
Monitor: The most popular input/output device is the monitor. A Keyboard is used to input data and Monitor is used to display the input data and to receive massages from the computer. A monitor has its own box which is separated from the main computer system and is connected to the computer by cable. It can be color or monochrome. It is controlled by an output device called a graphics card. Displayable area measured in dots per inch, dots are often referred to as pixels. Standard resolution is 640 by 480. Many cards support resolution of 1280 by 1024 or better. Number of colors supported varies from 16 to billions
Printer: It is an important output device which can be used to get a printed copy of the processed text or result on paper. There are different types of printers that are designed for different types of applications.

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