According to size computers can be divided into following types:
1. Super Computers:
Super computers are the fastest, largest and costliest computers available. The speed is in the 100 million instructions per second range. They tend to be used for specific applications in weather forecasting, aircraft design and nuclear research. Super computers are sometimes used for time sharing as well. Memory size is in hundreds of megabytes.
2. Mainframe Computers:
Mainframes are the traditional medium and large scale computer systems used in most business organizations for information processing.
A mainframe typically has a advanced control system and is capable of linking up
with dozens of input/output units and even minis for additional computer power. It can usually perform from 16 MIPS to onward. Memory size is from 2 MB to onward. Examples are IBM 4300 and 3300 series, Honeywell 700 series and NCR 800 series.
3. Mini Computers:
Mini computers have been very popular in business. Minis are frequently used to add computer power with mainframes. Sometimes an organization decides to decentralize or distribute its computer power to various stations or locations within user’s departments. Mini computers are ideal for processing data in a decentralized mode
since they are small. Moreover mini have also made it possible for many smaller organizations to afford a computer for the first time. The input/output devices are lesser as compared to mainframe. The speed is usually from 10 MIPS to onward. RAM is from 2 MB to onward.
4. Micro Computers:
The increasing use of micros in home, school, business and professional offices has been even more revolutionary. Although these computers have limited memory and speed, their cost makes them very attractive for applications that would otherwise not be feasible. Moreover micros are frequently used to provide additional computer power for companies that already have mainframes or minis. These are rare input/output devices with micro computers. It is mostly used as a single user. Its speed is usually counted in MHz rather than MIPS. The speed is generally from 8 MHz to onward. The RAM is from 640 KB to onward.