Input and Output Devices
A wider variety of input and output devices are used for communication with the computer. We will describe some commonly used input and output devices.
Keyboard is the most commonly used input devices. A keyboard is used to enter information and instruction in to a computer. It consists of a set of keys similar to that used in a typewriter. It has some special keys like Ctrl, All, Esc, return, function keys etc. in addition to those in a typewriter. These keys have special functions. The layout is similar to that of a typewriter.
Mouse is also an input device which provides a keyboard for entry of instruction. It is a hand held printing devices which can be used to move the cursor on the screen of VDU and required action is chosen by processing a button on the back of the mouse.
A microphone is used with sound to record speech and other sounds.
A scanner reads graphics and text in to a computer; scanners are available in various sizes.
Video Display Unit is the most commonly used output device. It is similar to a Television which uses Cathode Ray Tub (CRT) for display. Information (text and images) can be quickly displayed on the screen of a VDU. Several types of VDU’s are used in a computer e.g. CGA, VGA, EGA, etc. These are available with both colour black and white screen. The size of a monitor is measured diagonally across the screen. A screen of such VDU generally contains 24 lines of text with 80 characters in each line.
Printer is an output device which facilitates printing of the output on paper, one line of character at a time. Varieties of printers are available with various printing speeds and quality of printing. Some are briefed below:
Plotters are useful for producing high quality line graphs, maps and plans. They are available in many sizes. A plotters draws lines on paper using pens. Some models can produce coloured output by selecting coloured pens from a pen holder. The required pen is picked up from the stand and moved on the paper under software control. A combination of movements creates pictures and graphs. It is a slow device.
Speakers are used to listen sounds created by a sound card in a computer.