EXTERNAL DEVICES

·                 Provide a means of exchanging data between the external environment          and the computer.

·       Peripheral device - An external device connected to an I/O module.

·       Three categories:

1)   Human  readable

·       Suitable for communicating with the computer user

Eg : Video display terminals (VDTs), printers

2)   Machine readable

·       Suitable for communicating with equipment

Eg : Magnetic disk and tape systems, sensors and   actuators

3)   Communication

·       Suitable for communicating with remote devices such as a terminal, a machine readable device, or another computer

External Devices

 

A computer is somewhat similar to a human being.  We consist not only of a brain giving us the ability to think and to memorize, but also of the eyes, the ears, the hands etc. which connect us with the external world. A computer needs also additional external devices to communicate with its surroundings.

 

Contents

 

2.1 Input Devices

2.2 Output Devices

2.3 Standard Devices

 

2.1 Input Devices

 

For a computer, the Input devices have the same meaning as the senses for us. Just as we reach the information from our surroundings through our eyes, ears, touch, smell etc., a computer uses the input devices to get data.

 

There is a plenty of input devices available today. The most important are the keyboard and the mouse which I will explain separately.

 

Let's mention here only some of the input devices.

• Scanners: to digitalize the text and graphics in printed books, newspapers etc.
• Microphones: to input the sound data. Recently, speech input is about to be developed sufficiently well to enable one to navigate through the graphical user interface or to dictate texts.
• Sensors: to get measuring data into the computer. There are different kinds of sensors available like photo cell, thermic sensors etc. Most of them are used in robotics, automation and sciences.

 

 

2.2 Output Devices

 

Through the output devices we get the results of the computation made on all the input data. An output device is for a computer something like our mouth for us or our hands with which we can write.

 

The most important output device is the computer screen or display. I will speak about it separately.

 

Some other output devices are:

• Loudspeakers or headphones attached to the sound card: used as an alternative for the computer screen by screen reading programs, as phonetic support for vocabularies and language courses, as audio enrichment for the games etc.
• Printers
• Braille displays: used as an alternative computer screen access for the blind. Although predominantly an output device, Braille display includes also some input abilities.
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2.3 Standard Devices

 

We can say that a computer necessarily needs the standard input and output devices to be completely applicable. These devices are keyboard, mouse and display. I introduce all of them separately.