A computer is an electronic device which processes the data given to it as input and gives us the output in the form of meaningful information. These days it is almost impossible to carry out day to day operations in banks, government offices, shops, companies, etc without using the computers. However, different types of computers are required for different operations i.e. a computer required at home is different from the computer used for scientific operations and so on. The speed of a computer is measured in Hertz (Hz) i.e. how many calculations a computer can carry out within a second, e.g. a computer having a speed of 2 GHz (Giga Hertz) can process 200 million instructions per second. Depending upon the speed and memory capacity, computers are classified as follows:
Personal Computer (PC)
This is the most basic type of computer which is generally used at homes for internet surfing, to prepare power points, MS office related activities, playing games etc. This type of computer comes with a processing speed of some GHz with the processor installed on a single chip. These are single user based computers, however, these can be connected to form a network.
A workstation is a computer used for engineering applications (CAD/CAM), desktop publishing, software development, and other such types of applications which require a moderate amount of computing power and relatively high-quality graphics capabilities.
Common operating systems for workstations are UNIX and Windows NT. Like PC, workstations are also single-user computers like PC but are typically linked together to form a local area network, although they can also be used as stand-alone systems.
A computer that is smaller, less expensive, and less powerful than a mainframe or supercomputer but more expensive and more powerful than a personal computer. Minicomputers are used for scientific and engineering computations, business-transaction processing, file handling, and database management, and are often now referred to as small or midsize servers.
A mainframe computer is very large in size and expensive which is capable of supporting hundreds or even thousands of users simultaneously. Mainframe executes many programs concurrently and supports much simultaneous execution of programs.
Supercomputers are one of the fastest computers currently available. Supercomputers are very expensive and are employed for specialized applications that require the immense amount of mathematical calculations (number crunching).
For example, weather forecasting, scientific simulations, (animated) graphics, fluid dynamic calculations, nuclear energy research, electronic design, and analysis of geological data (e.g. in petrochemical prospecting).
Summit is the fastest supercomputer of the world as per June 2018. Pratyush is the fastest supercomputer of India which ranked 39 in top 500 supercomputers of the world.