Computer Structure

The definition of a computer is as follows:

A computer is a collection of resources, including digital electronic processing devices, stored programs and sets of data, which, under the control of the stored programs, automatically inputs, outputs, stores, retrieves and processes the data, and may also transmit data to and receive it from other computers. A computer is capable of drawing reasoned conclusions from the processing it carries out.

From the hardware point of view the essential features of this definition are 'a collection of ... digital electronic processing devices'.

Computers vary enormously in size, processing power and cost. Nevertheless, all computers consist of one or more functional devices, each carrying out one or more of the tasks described above. Each device performs a precisely specified task, and connects to other modules via defined interfaces. Modules of the same type of computer may be exchanged, and new modules added, without modification to their internal workings. The phrase plug-compatible describes units which may be connected in this manner.

Mainframes, Minis and Micros

very broadly speaking, there are three classes of computers, according to their size and complexity. These classes are known as mainframes, minicomputers (or minis) and microcomputers (or micros).

Mainframes are large computers, comprising a number of free-standing units. Mainframes arc generally housed in specially designed, air-conditioned rooms. Connections between the units are made by wires running beneath the floor of the room. mainframes are very powerful, and support a number of applications running concurrently. Very large mainframes are known as supercomputers.

Minicomputers are smaller than mainframes, with several functional devices mounted in a rack in a single unit. Minicomputers do not generally require an air-conditioned environment. They are often to be found in laboratories, factories and offices. Minicomputers can support more than one application running concurrently, though not as many as mainframes.

Microcomputers are the newest addition to the computer family. They are small and cheap, and are (generally) contained in a few small units. Their distinguishing feature is that processing is carried out on a single microprocessor chip. Although they are very versatile microcomputers can only support one application at any one time.

The classification of computers into mainframes, minis and micros is only very approximate. Computers are getting smaller and more powerful all the time Micros are being introduced with the capability of minis only a few years old. Minicomputers are incorporating microprocessors to assume the capability of mainframes.

1. what do you understand by the expression ‘plug compatible’?

2. Describe the way in which mainframes are usually accomodated.

3. How are the free-standing units of a mainframe connected?

4. Do the mainframes run applications singly?

5. What features of a minicomputer (apart from itd size) differ from those of a mainframe?

6. Where might one typicallt find a minicomputer in use?

7. What is the single most distinctive feature of the microcomputer?

8. Is it possible for a microcomputer to support more than one application running concurrently?

9. Why do you think the writer ends by saying this classification (of computers) is only very approximate?

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