On the basis of functions: Computers can be classified into three differentcategories : 1. ANALOG COMPUTERS 2. DIGITAL COMPUTERS 3. HYBRID COMPUTERS
ANALOG COMPUTERS : It operates on mathematical variables that change with continuously varying physical qualities such as, electric current, pressure, temperature, time etc. Such computers are single-problem-oriented that is specific to a particular task.
DIGITAL COMPUTERS : It operates with the discrete (discontinuously varying) signals in the form of numbers especially zeros and ones. Such computers are many problems oriented Ex: IBM-PC, Apple, Macintosh, and other available in the market.
HYBRID COMPUTERS : It is a combination of analog and digital computers. Which uses a special device called MODEM to convert analog signal to digital and vice versa. The full form of MODEM is Modulator and Demodulator. Information can be transferred to geographically dispersed areas through computers by the use of MODEM.
On the basis of size: Computers are classified intoFour groups according to their size and speed. 1.Super Computers 2.Mainframe Computers 3.Mini Computers 4.Micro Computers
Super Computers : They are the fastest and the most expensive machines, and are considered national resources. Some of the areas in which super computers are being used are Weather forecasting, biomedical research and aircraft design.
Mainframe Computers Mainframes are installed in large rooms. It occupies a large amount of space due to its accompanying services such as banks of magnetic disk, magnetic tape, high- speed printers, modems and several terminals. It can perform very complex scientific calculations, and they are mostly used for scientific purposes. They are also used where the company has its operations in different cities or different countries, such as Banks, such as Credit Card companies. More than 100 users can work at a time simultaneously without degrading its performance. Ex: CYBER-76,IBM 3000, UNIVAC 1180 etc
Mini Computers Physically it may be smaller, in comparison, to the Mainframe, Like the Mainframe; many users can simultaneously work on them. It is used for controlling manufacturing processes. They are mainly used in large business houses.Ex POP 11/73, HP 300,VAX 11,PRIME etc.
Micro Computer :We can accommodate it on a desk and only one person can use it at time. Therefore, the term Personal Computer (PC) has been given to such computers. These are used for small business, office administration purpose and even in playing games.EX: IBM PC XT/AT, COMPAQ,ACER AST EPSON etc