Another classification of computer is by size and their processing power. Here are the following categories :
- Mainframe computers.
Supercomputers – these are the most powerful type of computers. It is a very powerful and could cost several millions of dollars. They are useful in such areas as nuclear physics, vology, petroleum, engineering, telecommunication and military. A single supercomputer can easily forecast the weather worldwide. NASA in USA uses supercomputers to track and control space explorations. Supercomputers are sometimes referred to as “monster”.
Mainframe Computers – The mainframe computer is also a big computer which is used in very large organisations to perform a wide variety of functions. However, the size is nowhere near a monster. A mainframe can serve several users at a time and can have several devices for input and output. A mainframe normally supports network systems. This means that data can be input on a terminal located many kilometres away from the central processing unit (CPU). The size of the main memory is many times than that of a microcomputer. In modern day networking, mainframes are used by big organisations as “SERVERS” (host computers) that other computers scattered in different locations are connected to. Example of mainframes are IBM ES/9000, CRANE, etc.
Minicomputer – the minicomputer is a medium-sized computer which is smaller, slower and less expensive than the mainframe. It can do most of the jobs that a mainframe can do but on a reduced scale. They support limited number of users, input and output devices at the same time e.g a department. Example of minicomputers are DEC, VAX, RANSE, PDP11, etc.
Microcomputer – microcomputers are the smallest sized computers. They are computers in which each of their Central Processing Unit (CPU) was implemented using a microprocessor. The microcomputer is very easy to use and very cheap. It is also called a personal computer or a desktop computer. Microcomputers are sub-divided into:
- Pen based system.
Desktop systems are fashioned to sit on top of a desk or table and are primarily made up of three elements: A monitor, system unit and keyboard. A monitor is the computer view screen that looks like a television set. The system unit is rectangular in shape that contains the main system components. While a keyboard is composed of buttons used to create letters, numbers, symbols and perform additional functions.
Transportable also called lug gables are the largest of the portable computer weighing 15 pounds or more. They usually run on electrical power.
Laptops are a little smaller than lug gables and usually weigh between 8 and 15 pounds. As the name indicates, laptop can be held and operated on your lap. They run on either electrical or battery power.
Notebooks are quickly becoming the most common or the portable computers. They weigh less than 7-8 pounds and are about the size actual notebook.
Palmtop the smallest of the portable categories is the palmtop also called the handheld. The handheld weights less than 2 pounds, operates on batteries and can be held in one hand and operated with the other. The handhelds are different from other portables in that they do not have keyboard. Example of palmtop is cell phone.