Dale - Computer Science Illuminated 26

Dale - Computer Science Illuminated 26 - was doubling each...

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Unformatted text preview: was doubling each year. This observation became known as Moore’s law.” 3 Transistors also were used for memory construction. Each transistor xxv represented one bit of information. Integrated-circuit technology allowed Preface memory boards to be built using transistors. Auxiliary storage devices were still needed because transistor memory was volatile; that is, the information went away when the power was turned off. The terminal, an input/output device with a keyboard and screen, was layer, such as generation. The keyboard gave the user direct introduced during this George Boole and Ada Lovelace, to those who have contributed immediate response. access to the computer, and the screen providedto the communications layer, such as Doug Grace Murray Hopper Engelbart and Tim Berners-Lee. These Fourth Generation (1971–?) biographies are designed to give the reader Large-scale integration characterizes the fourth generation. From several some historical perspective and awareness thousand transistors to a silicon chip in the early 1970s, we moved to a of the men and women who contributed whole microcomputer on a chip by the middle of the decade. Main and are contributing today to the world of memory devices are still made almost exclusively out of chip technology. computing. Over the previous 40 years, each generation of computer hardware had Our second feature, Callouts, are sidebecome more powerful in a smaller package at lower cost. Moore’s law bar sections that include interesting tidbits was modified to say that chip density was doubling every 18 months. of information about the past, present, and By the late 1970s, the phrase personal computer (PC) had entered the future. They are garnered from history, vocabulary. Microcomputers had become so cheap that almost anyone from today’s newspapers, and from the could have one. And a generation of kids grew up playing PacMan. Ethical Issues authors’ experiences. These little vignettes The fourth generation found some new names entering the commercial are designed to amuse, to inspire, and to market. Apple, Tandy/Radio Shack, Atari, Commodore, and Sun joined the intrigue. big companies of earlier generations—IBM, Remington Summary Our third feature is the Ethical Issues Rand, NCR, DEC, Hewlett Packard, Control Data, and Computers are multimedia devices that manipulate data varying in form section included in each chapter. These Burroughs. The best-known success story of the from numbers to graphics to video. Because a computer can only manipulate binary values, all forms of data must be represented in binary form. sections are designed to illustrate that along personal computer revolution is that of the Apple. Steve Data is classified as 1970s had half words (2 bytes or 16 bits),discrete (digital). double being continuous (analog) or full words (4 bytes), and with the advantages of computing comes words (8 bytes). Integer values are represented their binary equivalent, using one computers 32-bit machines Wozniak, an engineer, and Steve Jobs, a high-school several techniques forModern or 64-bitbynegative numbers,(such as Intel’s Pentiumandof representing are often (such as Compaq’s Alpha processors III such a sign magniprocessor) machines responsibility. Privacy, hacking, viruses, and numbers are represented 500 Intel’s Itanium processor). some microprocessors Fr complement. Realas to the machines. The computingtriple made student, created a personal computer kit and marketed it tude or one’som a garage pagersHowever,Fortuneby athat are used in applications such are 8-bitan exponent that specifies the machine you up of the sign, the digits in the number, and free speech are among the topics discussed. are using, Steve is, is ultimately supported by the binary number and Jobs and Steve between computers out of a garage. This was the beginning of Apple radix Boyhood friends whatevertoitexplore about the relationshipWozniak system. point. We have more 44 A character set is a list of alphanumeric characters many kindscodes and At the end of each chapter’s exercises we binary numbers. In the next chapter we examine and sold their respective Volkswagen van and the of data that Computer, a multibillion-dollar company. represent each one. The most common character set is Unicode (16 bits for include a selection of Thought Questions. programmable calculator to raise the money to is suffiThe IBM PC was introduced in 1981 and soon was each character), which has ASCII as a subset. The 8-bit ASCII set cient finance their new for other (orcompany. Their first for English but not computer multiple) languages. There are Among the questions presented here are followed by compatible machines manufactured by many various ways for 50 Apple Is, the that it takes less space tohad it or sale was compressing text so computer that they store questions relating to the ethical issue less time to transmit it from one machine to another. other companies. For example, Dell and Compaq were Audio information is represented as digitized six short Color is designed and built in a garage. In sound waves. presented in the chapter. years Apple was that represent Fortune 500, the successful in making PCs that were compatible with IBM represented by three values listed in the the contribution of each of red, blue, and green. There are two basic techniques for representing pictures, youngest firm on this prestigious list. W W PCs. Apple introduced its very popular Macintosh micro- bitmaps and vector graphics. Video is broken up intoW a series of still images, each of which is represented as a picture. Color and Typography are Signcomputer line in 1984. From 1943 until her death on New Year’s Day in 1992, Admiral Grace Murray Hopper was intimately involved with computing. In 1991, she was awarded the National Medal of Technology “for her pioneering accomplishments in the development of computer programming languages that simplified computer technology and opened the door to a significantly larger universe of users.” Admiral Hopper was born Grace Brewster Murray in New York City on December 9, 1906. She attended Vassar and received a Ph.D. in mathematics from Yale. For the next 10 years, she taught mathematics at Vassar. In 1943, Admiral Hopper joined the U.S. Navy and was assigned to the Bureau of Ordnance Computation Project at Harvard University as a programmer on the Mark I. After the war, she remained at Harvard as a faculty member and continued work on the Navy‘s Mark II and Mark III computers. In 1949, she joined Eckert-Mauchly Computer Corporation and worked on the UNIVAC I. It was there that she made a legendary contribution to computing: She discovered the first computer “bug”—a moth caught in the hardware. Admiral Hopper had a working compiler in 1952, a time when the conventional wisdom was that computers could do only arithmetic. Although not on the committee that designed the computer language COBOL, she was active in its design, implementation, and use. COBOL (which stands for Common Business-Oriented Language) was developed in the early 1960s and is still widely used in the business data processing. Admiral Hopper retired from the Navy in 1966, only to be recalled within a year to fulltime active duty. Her mission was to oversee the Navy’s efforts to maintain uniformity in programming languages. It has been said that just as Admiral Hyman Rickover was the father of the nuclear navy, Rear Admiral Hopper was the mother of computerized data automation in the Navy. She served with the Naval Data Automation Command until she retired again in 1986 with the rank of Rear Admiral. At the time of her death, she was a senior consultant at Digital Equipment Corporation. During her lifetime, Admiral Hopper received honorary degrees from more than 40 colleges and universities. She was honored by her peers on several occasions, including the first Computer Sciences Man of the Year award given by the Data Processing Management Association, and the Contributors to Computer Science Education Award given by the Special Interest Group for Computer Science Education, which is part of the ACM (Association for Computing Machinery). Admiral Hopper loved young people and enjoyed giving talks on college and university campuses. She often handed out colored wires, which she called nanoseconds because they were cut to a length of about one foot—the distance that light travels in a nanosecond (billionth of a second). Her advice to the young was, “You manage things, you lead people. We went overboard on management and forgot about the leadership.” When asked which of her many accomplishments she was most proud of, she answered, “All the young people I have trained over the years.” 79 posts The layers into which the book is divided are color coded within the text. The color of the outside layer of the onion pictured on each chapter opener corresponds to the layer of that chapter. The same color is repeated in bars across the top of the pages of the layer. For each chapter, the slide on the side of the chapter opener shows where WWW Napster In 1999, Shawn Fanning launched a file-sharing program that took the music industry by storm, rapidly gaining the praise of millions and the criticism of many. Nineteen-year-old Shawn had only recently dropped out of his first year at Northeastern University to pursue a solution to the difficulty of downloading and exchanging music over the Net. With the support of his uncle, Shawn tackled this problem with dedication and ingenuity and, in a few months, developed an answer. Shawn wrote source code that wove together a search engine, file sharing, and Internet Relay Chat, making it possible for anyone to easily access and trade music files. Napster was born, and with it a fresh controversy over intellectual property rights and privileges. ...
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