Classification of Computers
Based on size, performance, storage, users, cost and other factors computers are classified into four types. Generally, a computer with high processing speed and large internal storage is called a big computer. There are Mainframe Computers, Minicomputers, Microcomputers and Supercomputers.
Mainframe computers
They are very large, often filling an entire room with an air-conditioner. These are also very expensive. They can store enormous of information, can perform many tasks at the same time, can communicate with many users at the same time. The price of a mainframe computer frequently runs into the millions of dollars. It also has multiple processors.
Large mainframe systems can handle the input and output requirements of several thousand of users. There are very few in India. Mainframe computers usually have many terminals connected to them. These terminals look like small computers but they are only devices used to send and receive information from the actual computer using wires. Terminals can be located in the same room with the mainframe computer, but they can also be in different rooms, buildings, or cities. Large businesses, government agencies, and universities usually use this type of computer. Examples are IBM 3380 or S/390 mainframe can support 50,000 users simultaneously.
The users often access the mainframe with terminals or personal computers. There are basically two types of terminals used with mainframe.
i) Dumb Terminal: Dumb terminal does not have its own CPU and storage devices. This type of terminal uses the CPU and storage devices of mainframe system. Typically, a dumb terminal consists of monitor and a keyboard (or mouse).
ii) Intelligent Terminal: Intelligent terminal has its own processor and can perform some processing operations. Usually, this type of terminal does not have its own storage. Typically, personal computers are used as intelligent terminals. A personal computer as an intelligent terminal gives facility to access data and other services from mainframe system. It also enables to store and process data locally.
The mainframe computers are specially used as servers on the World Wide Web. The mainframe computers are used in large organizations such as Banks, Airlines and Universities etc. where many people (users) need frequent access to the same data, which is usually organized into one or more huge databases. IBM is the major manufacturer of mainframe computers. The examples of mainframes are IBM S/390, Control Data CYBER 176 and Amdahl 580 etc.
Mini computers
They are much smaller than mainframe computers and they are also much less expensive. The cost of these computers can vary from a few thousand dollars to several hundred thousand dollars. They possess most of the features found on mainframe computers, but on a more limited scale. They can still have many terminals, but not as many as the mainframes. They can store a tremendous amount of information, but again usually not as much as the mainframe. Medium and small businesses typically use these computers. Minicomputers are commonly used as servers in network environment and hundreds of personal computers can be connected to the network with a minicomputer acting as server like The first minicomputer was introduced in the mid-1960s by Digital Equipment Corporation (DEC). After this IBM Corporation (AS/400 computers) Data General Corporation and Prime Computer also designed the mini computers.
Supercomputer:
Supercomputer is the most powerful and fastest, and also very expensive. It was developed in 1980s. It is used to process large amount of data and to solve the complicated scientific problems. It can perform more than one trillions calculations per second. It has large number of processors connected parallel. So parallel processing is done in this computer. In a single supercomputer thousands of users can be connected at the same time and the supercomputer handles the work of each user separately. Super computers are mainly used for:
Weather forecasting.
Nuclear energy research.
Aircraft design.
Automotive design.
Online banking.
To control industrial units.
The supercomputers are used in large organizations, research laboratories, aerospace centers, large industrial units etc. Nuclear scientists use supercomputers to create and analyze models of nuclear fission and fusions, predicting the actions and reactions of millions of atoms as they interact. The examples of supercomputers are CRAY-1, CRAY-2, Control Data CYBER 205 and ETA A-10 etc.
Microcomputer:
The microcomputers are also known as personal computers or simply PCs. Microprocessor is used in this type of computer.
These are very small in size and cost. The IBM’s first microcomputer was designed in 1981 and was named as IBM-PC. After this many computer hardware companies copied the design of IBM-PC. The term “PC-compatible” refers any personal computer based on the original IBM personal computer design. These computers are usually divided into desktop models and laptop models. They are excellent when used in small businesses, homes, and school classrooms. These computers are inexpensive and easy to use. They have become an indispensable part of modern life.
The most popular types of personal computers are the PC and the Apple. PC and PC-compatible computers have processors with different architectures than processors in Apple computers. These two types of computers also use different operating systems. PC and PC-compatible computers use the Windows operating system while Apple computers use the Macintosh operating system (MacOS). The majority of microcomputers sold today are part of IBM-compatible. However the Apple computer is neither an IBM nor a compatible. It is another family of computers made by Apple computer.
Microcomputers are further divided into following categories:
- Laptop computer,
- Workstation,
- Network computer and
- Handheld Computer
Laptop computer: Laptop computer is also known as notebook computer. It is small size (85-by-11 inch notebook computer and can fit inside a briefcase. The laptop computer is operated on a special battery and it does not have to be plugged until the battery needed to be charged. The laptop computer is portable and fully functional microcomputer. The memory and storage capacity of laptop computer is almost equivalent to the PC or desktop computer. It also has the hard dist, floppy disk drive, Zip disk drive, CD-ROM drive, CD-writer etc. it has built-in keyboard and built-in trackball as pointing device. Laptop computer is also available with the same processing speed as the most powerful personal computer. It means that laptop computer has same features as personal computer. Laptop computers are more expensive than desktop computers. Normally these computers are frequently used in business travelers.
Workstations: Workstations are special single user computers having the same features as personal computer but have the processing speed equivalent to minicomputer. A workstation computer can be fitted on a desktop. Scientists, engineers, architects and graphic designers mostly use these computers. Workstation computers are expensive and powerful computers. These have advanced processors, more RAM and storage capacity than personal computers. These are usually used as single-user applications but these are used as servers on computer network and web servers as well.
Network computers: Network computers are also version of personal computers having less processing power, memory and storage. These are specially designed as terminals for network environment. Some types of network computers have no storage. The network computers are designed for network, Internet or Intranet for data entry or to access data on the network. The network computers depend upon the network’s server for data storage and to use software. These computers also use the network’s server to perform some processing tasks.
In the mid-1990s the concept of network computers became popular among some PC manufacturers. As a result several variations of the network computers quickly became available. In business, variations of the network computer are Windows terminals, NetPCs and diskless workstations. Some network computers are designed to access only the Internet or to an Intranet. These devices are sometimes called Internet PCs, Internet boxes etc. In home some network computers do not include monitor.
Handheld computer: In the mid 1990s, many new types of small personal computing devices have been introduced and these are referred to Computers. The handheld computers sometimes called Mini-Notebook Computers. The type of computer is named as handheld computer because it can fit in one hand while you can operate it with the other hand. Because of its reduced size, the screen of handheld computer is quite small. Similarly it also has small keyboard. The handheld computers are preferred by business traveler. Some handheld computers have a specialized keyboard.
These computers are used by mobile employees, such as meter readers and parcel delivery people, whose jobs require them to move from place to place.