1. Microcomputer Microcomputer is at the lowest end of the computer range in terms of speed and storage capacity. Its CPU is a microprocessor. The first microcomputers were built of 8-bit microprocessor chips. The most common application of Personal Computers (PC) is in this category. The PC supports a number of input and output devices. An improvement of 8-bit chip is 16-but and 32-bit chips. Examples of microcomputer are IBM PC, PC-AT.
2. Mini Computer This is designed to support more than one user at a time. It possesses large storage capacity and operates at a higher speed. The mini computer is used in multi-user system in which various users can work at the same time. This type of computer is generally used for processing large volume of data in an organisation. They are also used as servers in Local Area Networks (LAN).
3. Mainframes There are organisations such as banks insurance companies process large number of transactions on-line. They require computers with very large disks to store several terabytes of data and transfer data from disk to main memory at several hundred megabytes/sec. The processing power needed from such computers is hundred million transactions per second.
These types of computer are generally 32-bit micro processors. They operate at very high speed, have very large storage capacity and can handle the work load of many users. They are generally used in centralised data bases. They are also used as controlling nodes in Wide Area Networks (WAN) Example of mainframes are DEC, ICL and IBM 3000 Series. IBM and Hitachi are a few manufacturers of mainframes.
4. Supercomputers They are the fastest and most expensive machines. They have high processing speed compared to other computers. They have also multi-processing technique. One of the ways in which supercomputers are built is by interconnecting hundreds of microprocessors. It should have a large main memory of around 16 GB and a secondary memory of 1000 6B.
Supercomputers are mainly being used for whether forecasting, biomedical research, remote sensing, aircraft design and other areas of science and technology. Examples of supercomputers are CRAY YMP, CRAY2, NEC, SX-3, CRAY XMP and PARAM from India.
5. Work Stations work stations are also desktop machines. They are however, more powerful providing processor speeds abut so times that of PCS. Most workstations have a large colour video display unit (19 inch monitors). Normally, they have main memory of around 256 MB to 4 GB and Hard disk of 80 to 320 6B. Work station normally use RISC processors such as MIPSCSIG). RIOS (IBM); SPARC (SUN), or PA-RISC (HP) Some manufactures of work station are Silicon Graphic (SIG), IBM, SUN Micro System and Hewlett Packard (HP). The standard operating System of work stations is UNIX and its derivatiraves such as AIX (IBM) Solaris (SUN) and HP UX (HIP).