sample-1 - 6 INTRODUCTION CHAP. 1 1.2 HISTORY OF OPERATING...

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6 INTRODUCTION CHAP. 1 1.2 HISTORY OF OPERATING SYSTEMS Operating systems have been evolving through the years. In the following sections we will briefly look at a few of the highlights. Since operating systems have historically been closely tied to the architecture of the computers on which they run, we will look at successive generations of computers to see what their operating systems were like. This mapping of operating system generations to computer generations is crude, but it does provide some structure where there would otherwise be none. The first true digital computer was designed by the English mathematician Charles Babbage (1792–1871). Although Babbage spent most of his life and for- tune trying to build his ‘‘analytical engine,’’ he never got it working properly because it was purely mechanical, and the technology of his day could not pro- duce the required wheels, gears, and cogs to the high precision that he needed. Needless to say, the analytical engine did not have an operating system. As an interesting historical aside, Babbage realized that he would need software for his analytical engine, so he hired a young woman named Ada Lovelace, who was the daughter of the famed British poet Lord Byron, as the world’s first programmer. The programming language Ada ® is named after her. 1.2.1 The First Generation (1945–55) Vacuum Tubes and Plugboards After Babbage’s unsuccessful efforts, little progress was made in constructing digital computers until World War II. Around the mid-1940s, Howard Aiken at Harvard, John von Neumann at the Institute for Advanced Study in Princeton, J. Presper Eckert and William Mauchley at the University of Pennsylvania, and Konrad Zuse in Germany, among others, all succeeded in building calculating engines. The first ones used mechanical relays but were very slow, with cycle times measured in seconds. Relays were later replaced by vacuum tubes. These machines were enormous, filling up entire rooms with tens of thousands of vacuum tubes, but they were still millions of times slower than even the cheapest personal computers available today. In these early days, a single group of people designed, built, programmed, operated, and maintained each machine. All programming was done in absolute machine language, often by wiring up plugboards to control the machine’s basic functions. Programming languages were unknown (even assembly language was unknown). Operating systems were unheard of. The usual mode of operation was for the programmer to sign up for a block of time on the signup sheet on the wall, then come down to the machine room, insert his or her plugboard into the com- puter, and spend the next few hours hoping that none of the 20,000 or so vacuum tubes would burn out during the run. Virtually all the problems were straightfor- ward numerical calculations, such as grinding out tables of sines, cosines, and log- arithms.
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SEC. 1.2 HISTORY OF OPERATING SYSTEMS 7 By the early 1950s, the routine had improved somewhat with the introduction
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