Microcomputer
Microcomputers are programmable electronic information processing machines whose controlling circuits are combined into one solid state (entirely nonmechanical) component called a central processing unit (CPU). Microcomputers can perform complex arithmetic and logic operations faster and more reliably than is possible manually. Some machines fitting this description carry other names, such as programmable calculators and microcontrollers, but the most familiar microcomputers are the general purpose personal computers, which include desktop, laptop, notebook, and hand-held models. In addition, specialized microcomputers are used in automobile ignitions, telephones, microwave ovens, video recorders and games, robots, public safety vehicles (fire, police and emergency medical), cash registers, warehouses, vehicle fleet management, heating and cooling systems, elevators, weapons systems, and many other devices. Growing microcomputer use has produced new occupations and increased the educational requirements for many already existing jobs.
Like other general-purpose computers ( mainframe computers, minicomputers, and supercomputers) most microcomputers handle information in digital format--that is, as numerical digits which can be manipulated according to rules of arithmetic and logic. Since most real-world information is in non-digital format (called linear, continuous or analog format) digital computers must convert information from analog to digital form. For example, the keyboard converts numbers and letters to numerical codes, and most pictures and graphics images are broken down, or digitized, into millions of separate dots called pixels, all of whose characteristics can be described with numbers. Since the simplest method of representing digits electronically is with the on/off control of electrical current, digital computers use a binary (base two) number system consisting of only the digits "1" for "on" and "0" for "off." Most computers therefore are essentially assemblies of millions of switches wired together, each switch controlling the status of a single digit.
The types and speed of a microcomputer's operations are determined largely by its CPU, the random access memory available to the CPU, the programmed instructions sent to the CPU (software), and the accessories coordinated by the CPU (peripherals). Some software programs control internal system operations (operating system and utilities programs), and others apply the computer's power to specialized problems (application programs). Each type is simply a stored command list the computer executes one-by-one, a method known as sequential or serial processing. A few advanced microcomputers, some minicomputers and most supercomputers can execute many commands simultaneously. Most microcomputers are limited to serial processing because they are typically controlled by only a single CPU. For this reason, microcomputer speed is determined mainly by the processing speed of its CPU, and by the speed with which the peripherals serve the needs of the CPU.
Today's microcomputer peripherals include: input devices —commonly keyboards, numerical keypads, and mice, and sometimes optical scanners, musical keyboards, barcode readers, light pens, microphones, remote sensors, and video cameras; output devices--commonly printers and video monitors, and sometimes plotters, speakers, and switching devices; storage devices--such as hard and floppy magnetic disk drives, magnetic tape drives, optical disk drives, and solid state devices such as read only memory (ROM) chips; and communications devices--such as modems for telephone communication, networks for linking several computers, and even radios for wireless communication.
Microcomputers were made possible by a series of increasingly miniature electronic inventions using naturally occurring elements such as silicon and germanium. They were found able to function electrically as either conductors or insulators, depending on the current flowing to them. Called semiconductors, their variability enabled them to serve as the first non-mechanical, or solid state, switches. Moreover, semiconductors function regardless of their size, at microscopic--even molecular--dimensions. These and other semiconductor properties were the basis of several landmark inventions leading to the microcomputer, including:
1947: Transistors—current flow controllers much smaller and simpler than the vacuum tubes they replaced;
1959: Integrated circuit (IC) chips—miniature circuits with many transistors, capacitors and resistors, located on one semiconductor chip, mass produced rather than individually wired by hand;
1969: Random access memory (RAM) IC chips—specialized ICs for storing hundreds of thousands of information bits, much smaller than the magnetic core computer memories they replaced;
1971: Microprocessor IC chips—the "computer on a chip" containing, for the first time in history, all of the circuits needed in the central processing unit of a computer (logic, arithmetic and control circuits). When combined with other IC chips containing data and program memory, the first microprocessors enabled the almost instantaneous creation of the first general-purpose microcomputers.
In fact, in 1971 personal microcomputer kits appeared on the market for hobbyists, but established electronics companies, including IBM, bypassed their first opportunity to design microcomputers, apparently unable to see the market potential which lay just ahead. What was needed in the early 1970s, in addition to the new microprocessor technology, was a process to design, build, test, finance, mass-produce and sell a totally new computing system--a group of new hardware and software products designed to work together to realize the potential of the microprocessor for low-cost personal computing. Today's sophisticated microcomputer systems evolved through the trials and errors of dozens of individuals and their firms.
The first widely available personal computer was the 1974 Altair from MITS (Micro Instrumentation and Telemetry Systems), for which college students William Gates and Paul Allen developed Microsoft BASIC, the first microcomputer operating system. The Altair was programmed with manual switches and perforated paper tape.
In 1977 many new microcomputers were developed, the most successful of which came from two California college students, Steve Jobs and Stephen Wozniak, who created Apple Computer Corporation to produce the Apple II computer.
Other 1977 notables were the TRS-80 Computer from Tandy/Radio Shack, the TI 99/4 from Texas Instruments, and the PET (personal electronic transactor) Computer from Commodore Computers. Commodore later produced the VIC-20 Computer (1981) and Commodore 64.
The Apple II, however, dominated the market until the IBM Personal Computer (IBM PC) appeared in 1981. Also notable in 1981 were the first portable computer (the Osborne 1) and the first computer assembled entirely in the United States which was priced under one hundred dollars (the Timex/Sinclair 1000).
While the Apple II Computer's success proved the feasibility of using microprocessor ICs for widespread, low-cost personal computing, the Apple II was not widely purchased by businesses, especially large corporations who were a potential market for literally millions of microcomputers. In July 1980 IBM's management saw this opportunity and decided to enter the microcomputer competition. With a one hundred fifty-member team based in Boca Raton, Florida, IBM designed, built and delivered the first IBM PCs thirteen months later. Within twelve more months IBM held twenty-eight percent of the personal computer market.
Thus began a rivalry between IBM and Apple Computer that continued for nearly ten years. Apple's strength was among home and school computer users. It also took the lead among graphics and publishing users with the unique, closely-guarded graphics technology of the Apple Macintosh Computer, introduced in 1984. The IBM PC (and, by 1985, hundreds of lower-priced imitations known as PC Clones), dominated the business microcomputer market.
In 1991, during a slump in most personal computer sales, IBM and Apple Computer shocked the industry when they announced an agreement to share technology and new product development. Their goals are to bridge the wide gap between IBM and Apple technologies, hoping to increase the competitiveness and sales of each company.
Today such semiconductor makers as Intel and Motorola produce millions of microprocessor ICs of all types. Each year the products have become more powerful and less expensive. Thousands of companies and individuals worldwide now assemble microcomputers, connecting ICs and other components simply by plugging them into standardized sockets on pre-wired circuit boards.
New ICs, software and peripherals have appeared frequently since 1971, permanently changing the computer business by making high-powered computers available to the average person. There is no foreseeable end to the process of invention in microcomputers. The most successful microcomputer companies have been those which were inventive at all levels--technology, product design, pricing, and marketing.
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