As we have seen a computer is an electronic machine which consists of a number of discrete elements. In addition to the electronic components there are a number of electro-mechanical units (such as printers) and, of course, the metal and plastic frames and covers which are used to support and enclose the complete assembly. Also necessary are the cables and connections which join the various parts together. Collectively all these physical units are referred to as hardware. Hardware alone, however, is not sufficient to make a practical computer for data processing purposes. To make a computer perform it needs instructions. Collectively all the things necessary to make the computer hardware operational are called software and it includes, therefore, such items as instruction manuals and documentation as well as programs. The trend, however, is to reserve the term ‘software’ for the various types of instructions which are actually put into the computer, and it is in this sense it will be used in this chapter.
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