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เนื้อหาย่อ : In the six years since this book was written there have been two major developments, which have radically changed the outlook of computer designers and users. These are the development of large semiconductor memories and microprocessors on a single chip. Both of these have emerged from the spectacular progress in the design of microcircuits. Minicomputers have been largely eclipsed by the appearance of powerful microprocessors at astonishingly low prices. The small computers now in use are usually based on an internal microprocessor with input-output and peripheral devices. Visual Display Units, which for some time had been regarded as the ideal general purpose input-output device, have at last reached the threshold of economic take-off, and are in common use. The more advanced examples of these also incorporate microprocessors. The general use of the all conquering microprocessor does not absolve users from having some knowledge of the principles of what is happening inside, even though they may never need to design one. An understanding of the internal operations is also a help to programming. The organisation of a microprocessor is not very much different to that of the minicomputer. To a great extent, the microprocessor evolved from the minicomputer, by shrinking the whole circuit on to one silicon chip. Reduction of the word size to 8 bits leads to some changes, but the newer 16 bit microprocessors are getting back to the equivalent of a 16 bit minicomputer. For this reason the organisation of a 16 bit minicomputer is still relevant to the present situation. In writing a book on computer design one either has to invent an architecture, or base it on an existing one, as has been-done here, using the NOV A mincomputer as an example. The NOVA has a sound architecture and still provides a good basis on which to discuss the principles of computer design. Chapter 1 has been revised to eliminate out-of-date material, and comments on the latest developments have been added. In logic design the emphasis has moved from the design of actual