Types of Computers–Based on Purposes, Signals and Capacity

Posted by Unknown Friday, July 19, 2013 0 comments
We are familiar with various names of commuters such as Micro, Mini, Mainframe and Supercomputers. Here we have divided computers based on purposes, signals and capacity. At first we shall discuss the classification of the computers based on purposes.

Classification based on purposes:
There are either special-purpose or general-purpose computers. A special-purpose computer is designed for a specific application. It is also known as dedicated computer. Many such computers have instructions permanently programmed into them that are designed to perform only one major function. Special-purpose computers are used to control traffic lights, to control the collection of tolls on highways, and in automobiles, weapons, appliances and games etc.

General-purpose computers are used to handle a variety of tasks. This is possible by the stored-program concept. By this concept, a program containing a series of instructions is prepared for an application and temporally stored in memory. Once stored in the computer’s memory, the program can be executed to perform the specific function. After the completion of the execution of one program, another program can be used for some other task. That is, the same hardware can be used to execute many different programs.

General-purpose computers are more versatile than special-purpose computer. But when applied to the same task it is seen that general-purpose computers are less efficient and also slower than special-purpose computers 

Classification based on signals:
Two types of computers based on internet signaling are analog computers and digital computers. An analog computer actually represents quantities by the physical analogies. These kinds of computer represent the physical quantities, such as distance, acceleration, velocity, temperature, or angular position, pressure, force etc. by electrical or mechanical parameters.

The example of an analog-computing device is automobile speedometer. It changes the rotating rate of the drive shaft of a car into the numerical value of the speed of the automobile. The example of an analog device is a thermometer. It converts the movement of a column of mercury into a temperature reading.

Analog computers are ideal in situations where data can be accepted straightly from measuring instruments. The capability to gather data at high speeds and to process data at uniformly high speeds, makes analog computers exclusively suited to controlling processes of oil refineries, weapon systems steel mills, and similar other procedures. An analog computer does not need any storage space ability. The out from an analog computer is usually in the form of reading on a dial (as in the speedometer of a car) or a graph plotted on paper.

Analog computers were in use before the invention of the digital computers. There are far more digital computers in use today than analog computers. 

Classification based on capacity:
Capacity of a computer refers to the volume of data that a computer system can process. Formerly a computer’s size was a sign of its capacity. With the current state of smallness, dimension of capacity is based on throughput of the computer. Throughput is the quantity of processing that can be performed in a given amount of time. Based on throughput computer systems can be divided into four major categories:
  • Microcomputers
  • Minicomputers
  • Mainframe computes
  • Supercomputers
Microcomputers:
Microcomputers are generally known as personal computers-PCs and are microprocessor based small notebook or laptop or desktop systems with changeable capacity. Personal digital assistants (PDAs) are very small portable computers. PDAs are also recognized as the palmtop computers. The brain of a microcomputer is the microprocessor; it is a silicon chip containing essential circuits to execute logic or arithmetic operations and to manage the input/output operations. A microprocessor is an integrated circuit which usually contains millions of transistors squeezed onto a small silicon chip. A microcomputer system is formed by adding input and output facility along with memory to the microprocessor.
Microcomputers
At the initial time the microcomputers had very limited processing power and limited choice of input/output devices. But at modern days they have wider processing capabilities and maintain a wide range of input/output devices. Today microcomputers are available with a collection of input/output devices varying from a tape recorder to a voice synthesizer. In addition to general-purpose computations, microcomputers are also used for exceptional purpose applications in automobiles, airplanes, toys, clocks, appliances etc.

Workstations: The High-end microcomputers are also recognized as workstations. They symbolize the bridge between the microcomputers and minicomputers. It is a microcomputer with many of the facilities and abilities of bigger minicomputers but price much less. At first it was designed for use by designers and engineers who need extremely powerful processing and output capabilities.

Servers: Servers are not designed to be used directly. They make programs and data available for users having access to a computer network. A computer network is a collection of computers connected together.

Clients: To use servers, users run desktop programs called clients, which know how to contact the server and obtain information from the server. Use of desktop clients and centralized servers is called client/server computing.

Terminals: Although terminals look like the personal computers, they have some limitations when compared with personal computers. Terminals have only a screen and a keyboard and the electronics that allow them to communicate with the computer to which they are connected. Because they lack the ability to process data on their own, they are called dumb terminals. There is a variety of dumb terminals that can perform limited processing. These are called smart terminals. A personal computer is an example of a smart terminal.

Minicomputers:
A minicomputer system performs the basic arithmetic and logic functions and supports some of the programming language used with large computer systems. They are physically smaller, less expensive, and have small storage capacity compared to mainframes. Minicomputers are ideally suited for processing tasks that do not require access to huge volumes of stored data. As a result of low cost, ease of operation, and versatility, minicomputers have gained repaid acceptance since their introduction in the mid-sixties. Some of the larger and expensive minicomputers are capable of supporting a number of terminals in a time-shared mode. Uses of minicomputers are gradually being diminished with the rapid development of microcomputers.
Minicomputers
Mainframe Computers:
A larger computer normally consists of modules accumulated on a chassis and is terms as a mainframe computer. They differ in size, from those a little larger than a minicomputer to supercomputers. These computer systems present extensive benefits over minicomputers or microcomputers. Some of these are: greater storage facility, greater processing speed, a larger assortment of input/output devices, and support for a number of high-speed storage devices, multiprogramming, and time sharing.

Owing to wonderful expense, a mainframe computer system must be operated powerfully. Operating mainframes at the necessary level of effectiveness requires a very large and highly trained staff. These are normally used by government agencies, large business, military and the universities. These systems are often coupled with other computer systems in a large network to give massive computing power. This is referred to as a distributed data processing system. 

Supercomputer:
A very powerful and large mainframe computer is known as a supercomputer. The astronomical cost of super-computers has limited their development to only a few hundred worldwide. The example of a supercomputer is the Cray X-MP. Such supercomputers are applied to the solution of very difficult and complicated scientific and technical problems. Supercomputers are also used for the various national security purposes of some advanced nations.

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