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Chapter 1 INTRODUCTION WHAT ARE COMPUTERS? Computers are devices consisting of electric circuits with electronic elements that act as switches and gates in the circuits. When computers were first built starting about 1945 the electronic elements were vacuum tubes. About 1959, tubes were discarded in favor of transistors. Then it was found that the electronic elements could be integrated into the circuits and produced by special “printing” techniques. By the 1980s the integrated circuits had been miniaturized to such an extent that major components of the computer could be "printed" on a chip of silicon smaller than a fingernail. Today we can obtain desk top computers for personal use that are as powerful as ones that sold for over a million dollars in the early 1960s. As the cost of computers has dropped in the last 25 years, the uses that have been found for them have skyrocketed. There is scarcely any part of our lives that has not been changed in some way due to computers. There has been what many refer to as a revolution in the way things are done. With the invention of the steam engine in the nineteenth century, machines were devised to handle physical materials: to transport them and shape them into useful objects. We had what was known as the industrial revolution . Computers are machines that handle information and process it so that it is useful to us. We have now what is called an information revolution , or a computer revolution . The revolution has been accelerated by the concurrent advances in the technology of telecommunications , which includes the use of satellites for long distance communication and the transmission of digital signals. The machines of the industrial revolution did physical work for us. The machines of the information revolution do mental work for us. That is why the early computers were referred to as electronic brains . The way that a computer operates is to take in information, transform it, and then put the transformed information out. If the computer
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2 | INTRODUCTION transforms information in a fixed way, we would say it is a special purpose machine . Computers usually are general purpose machines . To operate, a computer must have in it a list of instructions which specifies how the information is to be transformed. This list of instructions is called a computer program . The information that is to be transformed is called data . A computer program can itself be read into a computer and this means that you can have various programs in the machine. This is why we say that our computers are general purpose; they can run, in sequence or in parallel, a variety of programs. Any computer that you intend to use must have some programs already stored in it so that you may read in your programs and have them operate. We call programs software ; the computer itself is the hardware . The software stored in the computer that allows users to enter programs and run them is called the operating system . Programs that transform data for you are called
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