When you read the following text, remember to try and understand the meaning of new words and expressions from the context. Don't check new words in the dictionary until you have read the whole text. Most of the words in boldtypeface are explained in the Glossary at the end of the book.
 Computers are machines designed to process, electronically, specially 1 prepared pieces of information which are termed data. Handling or manipulating the information that has been given to the computer, in such ways as doing calculations, adding information or making comparisons is called processing.Computers are made up of millions of 5 electronic devices capable of storing data or moving them, at enormous speeds, through complex circuits with different functions.
 All computers have several characteristics in common, regardless of make or design. Information, in the form of instructions and data, is given to the machine, after which the machine acts on it, and a result is 10 then returned. The information presented to the machine is the input;the internal manipulative operations, the processing;and the result, the output.These three basic concepts of input, processing, and output occur in almost every aspect of human life whether at work or at play. For example, in clothing manufacturing, the input is the pieces of cut 15 cloth, the processing is the sewing together of these pieces, and the output is the finished garment.
 Figure 3.1 shows schematically the fundamental hardware components in a computer system. The centerpiece is called either the computer, the processor,or, usually, the central processing unit (CPU).The term 20 'computer' includes those parts of hardwarein which calculations and
other data manipulations are performed, and the high-speed internal memory in which data and calculations are stored during actual execution of programs. Attached to the CPU are the various peripheral devicessuch as card readers and keyboards(two common examples of 25 input devices). When data or programs need to be saved for long periods of time, they are stored on various secondary memorydevices or storage devicessuch as magnetic tapes or magnetic disks.
 Computers have often been thought of as extremely large adding
machines, but this is a very narrow view of their function. Although a 30 computer can only respond to a certain number of instructions, it is not a single-purposemachine since these instructions can be combined in an infinite number of sequences. Therefore, a computer has no known limit on the kinds of things it can do; its versatility is limited only by the imagination of those using it. 35
 In the late 1950s and early 1960s when electronic computers of the kind in use today were being developed, they were very expensive to own and run. Moreover, their size and reliability were such that a large number of support personnel were needed to keep the equipment operating. This has all changed now that computing power has become portable, 40 more compact, and cheaper.
 In only a very short period of time, computers have greatly changed the way in which many kinds of work are performed. Computers can remove many of the routine and boring tasks from our lives, thereby leaving us with more time for interesting, creative work. It goes without 45 saying that computers have created whole new areas of work that did not exist before their development.