Today computers are everywhere. They have invaded our everyday lives and you will find some sort of computer in practically every electronic appliance, although it may not be obvious that a computer is present. It can control a variety of gadgets and appliances as well as being able to perform a variety of tasks in itself as a stand alone machine.
So what is a computer and what exactly can it do? What tasks can it perform? And what applications can it be used for? Most of us think of a computer as a box with a screen, a keyboard and perhaps a printing device attached. However, the keyboard is merely a means of getting information into the computer itself and the screen or printer a means of getting information out. In other words input and output devices.
A computer is a tool. A tool for processing information or data. In its simplest form it is just a number crunching device: a calculator. Yet it does this far faster than a human can. And the amount of data that can be processed per second is steadily increasing as advances in technology are made.
However, a computer can do more than just add and subtract. Although it can perform this task repeatedly many many times its advantage is that it can process more than just numbers. We can get it to process words as well: information. These words can act as commands to tell the computer to do something or they can be data such as a list of names that we might want sorted into alphabetical order. The information may be available at the time measurements are made ie it is evaluated 'now'. Such a system is referred to as real time. Alternatively, the information may be provided for future processing such as in a system simulation.
At the heart of every computer is the Central Processing Unit (CPU) which as its name suggests does all the processing or donkey work. In early computers it was an electronic chip all on its own and there were a number of other chips (or integrated circuits - ICs) which supported it. These latter chips performed a variety of tasks such as controlling the speed at which information flowed and where it went. Nowadays, many of these are able to be incorporated with the CPU in the same chip as scales of integration have increased. (For moredetail and/or a technical explanation please refer to the Bibliography.)
The CPU is combined in the chip with a number of other devices to form a microprocessor. A microprocessor from one manufacturer will perform differently to that from another. To distinguish a chip of one manufacturer from another they are given different numbers or names. One manufacturer may even produce a family of microprocessors which may vary slightly in what they can do. It will also be found that if you have one processor in your machine then you cannot use your programs with a different processor, although to confuse matters some processors are compatible with others. For example, in the early 1980s the BBC micro used a 6502 processor whereas the ZX Spectrum used a Z80. They could both perform the same tasks with programs written specially for them (eg wordprocessing) but you could not interchange the programs. Nor could you retrieve data on one which the other had output onto an external storeage device. Without being technical, this was because the microprocessors were arranged differently inside and the format in which the data was recorded.
Most computers have a basic cycle time, which is a measure of their operating speed, of the order of a microsecond or less (usually expressed in Hertz). In everyday life we have the cycle of a year, for example, or the seasons during which nature performs a number of tasks. The four stages of this cycle are Spring, Summer, Autumn and Winter. A computer, too, has its own repeating cycle. It needs to respond to various events. Most practical control/measuring systems have operating speeds or response times which are the order of a few milliseconds (kHz) to several days. Hence there is a speed disparity between the computer and its peripheral. An interface is designed to accomodate this and is usually activated under the control of the computer itself.
Parts of a computer Memory Types and Uses
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