A microprocessor is a general purpose central processing until of a digital computer system. It has arithmetic logical unit control circuits and a set of registers on a signal chip. To make it a complete systems ( called microcomputer) we have to add read only memory (FROM) random access memory (RAM) and number of input / output device through systems buses as shown in figure.
In college laboratories we have signal board microcomputers. These microcomputer have 8 to 16 bit microprocessor ROM RAM hex keyboard and seven segment LED display unit. A monitor program is stored in ROM less than 2 k bytes to interact memory and input/ output devices.
A larger microcomputer is known as personal computer used generally for personal or business purpose. It is equipped with many additional special purpose devices like floppy disk drive and hard disk drive for mass storage larger keyboard 108 or more keys CRT display monitor CD drive etc. In these computer operating systems is required instead of monitor program to interact with larger memory and various special purpose inputs/ output devices. Commonly used operating systems are DOS UNIX and many version of Microsoft windows ( 98 ,XP , ME, etc) such computer may be used in general purpose software applications.