The input devices are the keyboard and the mouse, and sometimes a scanner which may be either flat bed or hand held. A microphone may also be used to enable voice input to the computer.
The output devices are a monitor or display terminal, based on either a CRT (Cathode Ray Tube) or a LCD (Liquid Crystal Display); a printer; possible speakers or headphones if multimedia or voice applications are used.
The telephone may also be used as an input and output devices, connected to the PC via a modem.
The storage devices include the hard disk, tape streamers, floppy disks, CD (Compact Disc) and DVD (Digital Versatile Disc) ROMs.
A computer System in an industrial control facility, such as one controlling the distribution of a utility such as water, gas or electricity would have a different set of input and output devices from those listed above. The traditional keyboard and mouse and display terminal may not even be present in the control room although, they would be likely to present in a secure back office facility for maintenance and management purposes only.
The Point of Sale (POS) terminal as seen in many retail environments, provides us with our third example of different computer I/O in operation Devices include:
Barcode reader, and item selection panel.
Specialised equipment linked to the system such as till drawer and customer display.
A magnetic card swipe and modem or digital network connection for Electronic Funds Transfer (EFT).
A receipt printer.
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