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Microcomputer

From Wikipedia, the free encyclopedia
(Redirected fromMicrocomputers)
Small computer with a CPU made out of a microprocessor
"Microcomputing" redirects here. For the hobbyist magazine, seeKilobaud Microcomputing.
For asmall computer on anintegrated circuit, seemicrocontroller.
TheCommodore 64 was one of the most popular microcomputers of its era, and is the best-selling model ofhome computers of all time.[1]
Raspberry Pi, a popular modern-class microcomputer

Amicrocomputer is a small, relatively inexpensivecomputer having acentral processing unit (CPU) made out of amicroprocessor.[2] The computer also includesmemory andinput/output (I/O) circuitry together mounted on aprinted circuit board (PCB).[3] Microcomputers became popular in the 1970s and 1980s with the advent of increasingly powerful microprocessors. The predecessors to these computers,mainframes andminicomputers, were comparatively much larger and more expensive (though indeed present-day mainframes such as theIBM System z machines use one or more custom microprocessors as their CPUs). Many microcomputers (when equipped with akeyboard andscreen for input and output) are alsopersonal computers (in the generic sense). An early use of the term "personal computer" in 1962 predates microprocessor-based designs.(See "Personal Computer: Computers at Companies" reference below). A "microcomputer" used as an embedded control system may have no human-readable input and output devices. "Personal computer" may be used generically or may denote anIBM PC compatible machine.

The abbreviation "micro" was common during the 1970s and 1980s,[4] but has since fallen out of common usage.

Origins

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The termmicrocomputer came into popular use after the introduction of theminicomputer, althoughIsaac Asimov used the term in his short story "The Dying Night" as early as 1956 (published inThe Magazine of Fantasy and Science Fiction in July that year).[5] Most notably, the microcomputer replaced the many separate components that made up the minicomputer's CPU with one integrated microprocessorchip.

In 1973, the FrenchInstitut National de la Recherche Agronomique (INRA) was looking for a computer able to measure agriculturalhygrometry. To answer this request, a team of French engineers of the computer technology company R2E, led by its Head of Development,François Gernelle, created the first available microprocessor-based microcomputer, theMicral N. The same year the company filed their patents with the term "Micro-ordinateur", a literal equivalent of "Microcomputer", to designate a solid state machine designed with a microprocessor.

In the US the earliest models such as theAltair 8800 were often sold as kits to be assembled by the user, and came with as little as 256bytes ofRAM, and noinput/output devices other than indicator lights and switches, useful as aproof of concept to demonstrate what such a simple device could do.[6] As microprocessors andsemiconductor memory became less expensive, microcomputers grew cheaper and easier to use.

  • Increasingly inexpensive logic chips such as the7400 series allowed cheap dedicated circuitry for improveduser interfaces such askeyboard input, instead of simply a row of switches to toggle bits one at a time.
  • Use ofaudio cassettes for inexpensivedata storage replaced manual re-entry of a program every time the device was powered on.
  • Large cheap arrays of siliconlogic gates in the form ofread-only memory andEPROMs allowed utility programs and self-bootingkernels to be stored within microcomputers. Thesestored programs could automatically load further more complex software from external storage devices without user intervention, to form an inexpensiveturnkey system that does not require a computer expert to understand or to use the device.
  • Random-access memory became cheap enough to afford dedicating approximately 1–2 kilobytes of memory to avideo display controllerframe buffer, for a 40x25 or 80x25 text display or blocky color graphics on a common householdtelevision. This replaced the slow, complex, and expensiveteletypewriter that was previously common as an interface to minicomputers and mainframes.

All these improvements in cost and usability resulted in an explosion in their popularity during the late 1970s and early 1980s.A large number of computer makers packaged microcomputers for use in small business applications. By 1979, many companies such asCromemco,Processor Technology,IMSAI,North Star Computers,Southwest Technical Products Corporation,Ohio Scientific,Altos Computer Systems,Morrow Designs and others produced systems designed for resourceful end users or consulting firms to deliver business systems such as accounting, database management and word processing to small businesses. This allowed businesses unable to afford leasing of a minicomputer ortime-sharing service the opportunity to automate business functions, without (usually) hiring a full-time staff to operate the computers. A representative system of this era would have used anS100 bus, an8-bit processor such as anIntel 8080 orZilog Z80, and eitherCP/M orMP/M operating system.The increasing availability and power ofdesktop computers for personal use attracted the attention of more software developers. As the industry matured, the market forpersonal computers standardized aroundIBM PC compatibles runningDOS, and laterWindows. Modern desktop computers,video game consoles,laptops,tablet PCs, and many types ofhandheld devices, includingmobile phones, pocketcalculators, and industrialembedded systems, may all be considered examples of microcomputers according to the definition given above.

Colloquial use of the term

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Three microcomputer systems frequently associated with the first wave of commercially successful 8-bit home computers: The Commodore PET 2001, the Apple II, and the TRS-80 Model 1

By the early 2000s, everyday use of the expression "microcomputer" (and in particular "micro") declined significantly from its peak in the mid-1980s.[7] The term is most commonly associated with the most popular8-bithome computers (such as theApple II,ZX Spectrum,Commodore 64,BBC Micro, andTRS-80) and small-businessCP/M-based microcomputers.

In colloquial usage, "microcomputer" has been largely supplanted by the term "personal computer" or "PC", which specifies a computer that has been designed to be used by one individual at a time, a term first coined in 1959.[8] IBM first promoted the term "personal computer" to differentiate theIBM PC fromCP/M-based microcomputers likewise targeted at the small-business market, and also IBM's own mainframes and minicomputers.[citation needed] However, following its release, the IBM PC itself was widely imitated, as well as the term.[citation needed] The component parts were commonly available to producers and theBIOS wasreverse engineered throughcleanroom design techniques.IBM PC compatible "clones" became commonplace, and the terms "personal computer", and especially "PC", stuck with the general public, often specifically for a computer compatible with DOS (or nowadays Windows).

Description

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Monitors, keyboards and other devices for input and output may be integrated or separate. Computer memory in the form ofRAM, and at least one other less volatile, memory storage device are usually combined with the CPU on asystem bus in one unit. Other devices that make up a complete microcomputer system include batteries, apower supply unit, a keyboard and various input/output devices used to convey information to and from a human operator (printers,monitors,human interface devices). Microcomputers are designed to serve only one user at a time, although they can often be modified with software or hardware to concurrently serve more than one user. Microcomputers fit well on or under desks or tables, so that they are within easy access of users. Bigger computers likeminicomputers,mainframes, andsupercomputers take up largecabinets or even dedicated rooms.

A microcomputer comes equipped with at least one type of data storage, usuallyRAM. Although some microcomputers (particularly early 8-bit home micros) perform tasks using RAM alone, some form ofsecondary storage is normally desirable. In the early days of home micros, this was often a datacassette deck (in many cases as an external unit). Later, secondary storage (particularly in the form offloppy disk andhard disk drives) were built into the microcomputer case.

History

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A collection of early microcomputers, including aProcessor Technology SOL-20 (top shelf, right), an MITSAltair 8800 (second shelf, left), aTV Typewriter (third shelf, center), and anApple I in the case at far right

TTL precursors

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Although they did not contain any microprocessors, but were built aroundtransistor-transistor logic (TTL),Hewlett-Packard calculators as far back as 1968 had various levels of programmability comparable to microcomputers. The HP 9100B (1968) had rudimentary conditional (if) statements, statement line numbers, jump statements (go to), registers that could be used as variables, and primitive subroutines. The programming language resembledassembly language in many ways. Later models incrementally added more features, including theBASIC programming language (HP 9830A in 1971). Some models had tape storage and small printers. However, displays were limited to one line at a time.[9] TheHP 9100A was referred to as apersonal computer in an advertisement in a 1968Science magazine,[10] but that advertisement was quickly dropped.[11] HP was reluctant to sell them as "computers" because the perception at that time was that a computer had to be big in size to be powerful, and thus decided to market them as calculators. Additionally, at that time, people were more likely to buy calculators than computers, and, purchasing agents also preferred the term "calculator" because purchasing a "computer" required additional layers of purchasing authority approvals.[12]

TheDatapoint 2200, made byCTC in 1970, was also comparable to microcomputers. While it contains no microprocessor, theinstruction set of its custom TTL processor was the basis of the instruction set for theIntel 8008, and for practical purposes the system behaves approximately as if it contains an 8008. This is because Intel was the contractor in charge of developing the Datapoint's CPU, but ultimately CTC rejected the 8008 design because it needed 20 support chips.[13]

Another early system, theKenbak-1, was released in 1971. Like the Datapoint 2200, it usedsmall-scale integratedtransistor–transistor logic instead of a microprocessor. It was marketed as an educational and hobbyist tool, but it was not a commercial success; production ceased shortly after introduction.[14]

Early microcomputers

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In late 1972, a French team headed byFrançois Gernelle within a small company, Réalisations & Etudes Electroniques (R2E), developed and patented a computer based on a microprocessor – the Intel 8008 8-bit microprocessor. ThisMicral-N was marketed in early 1973 as a "Micro-ordinateur" ormicrocomputer, mainly for scientific and process-control applications. About a hundredMicral-N were installed in the next two years, followed by a new version based on the Intel 8080. Meanwhile, another French team developed the Alvan, a small computer for office automation which found clients in banks and other sectors. The first version was based on LSI chips with an Intel 8008 as peripheral controller (keyboard, monitor and printer), before adopting theZilog Z80 as main processor.

In late 1972, aSacramento State University team led by Bill Pentz built the Sac State 8008 computer, able to handle thousands of patients' medical records. The Sac State 8008 was designed with the Intel 8008. It had a full set of hardware andsoftware components: a disk operating system included in a series of programmable read-only memory chips (PROMs); 8 Kilobytes of RAM; IBM's Basic Assembly Language (BAL); a hard drive; a color display; a printer output; a 150 bit/s serial interface for connecting to a mainframe; and even the world's first microcomputer front panel.[15][16]

In early 1973,Sord Computer Corporation (nowToshiba Personal Computer System Corporation) completed the SMP80/08, which used theIntel 8008 microprocessor. The SMP80/08, however, did not have a commercial release. After the first general-purpose microprocessor, theIntel 8080, was announced in April 1974, Sord announced the SMP80/x, the first microcomputer to use the 8080, in May 1974.[17]

Virtually all early microcomputers were essentially boxes with lights and switches; one had to read and understand binary numbers and machine language to program and use them (the Datapoint 2200 was a striking exception, bearing a modern design based on a monitor, keyboard, and tape and disk drives). Of the early "box of switches"-type microcomputers, the MITSAltair 8800 (1975) was arguably the most famous. Most of these simple, early microcomputers were sold aselectronic kits—bags full of loose components which the buyer had to solder together before the system could be used.

Microcomputer module LSI-11/2

The period from about 1971 to 1976 is sometimes called thefirst generation of microcomputers. Many companies such asDEC,[18]National Semiconductor,[19]Texas Instruments[20] offered their microcomputers for use in terminal control, peripheral device interface control and industrial machine control. There were also machines for engineering development and hobbyist personal use.[21] In 1975, theProcessor TechnologySOL-20 was designed, which consisted of one board which included all the parts of the computer system. TheSOL-20 had built-in EPROM software which eliminated the need for rows of switches and lights. TheMITS Altair just mentioned played an instrumental role in sparking significant hobbyist interest, which itself eventually led to the founding and success of many well-knownpersonal computer hardware and software companies, such asMicrosoft andApple Computer. Although the Altair itself was only a mild commercial success, it helped spark a huge industry.

Home computers

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By 1977, the introduction of the second microcomputer generation asconsumer goods, known ashome computers, made them considerably easier to use than their predecessors because their predecessors' operation often demanded thorough familiarity with practical electronics. The ability to connect to a monitor (screen) or TV set allowed visual manipulation of text and numbers. TheBASIC language, which was easier to learn and use than raw machine language, became a standard feature. These features were already common inminicomputers, with which many hobbyists and early produces were familiar.

In 1979, the launch of theVisiCalcspreadsheet (initially for theApple II) first turned the microcomputer from a hobby for computer enthusiasts into a business tool. After the 1981 release by IBM of itsIBM PC, the termpersonal computer became generally used for microcomputers compatible with the IBM PC architecture (IBM PC–compatible).

See also

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Notes and references

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  1. ^Kahney, Leander (2003-09-09)."Grandiose Price for a Modest PC".Wired. Retrieved2019-11-04.
  2. ^"Microcomputer".dictionary.com.
  3. ^A.O., Williman; Jelinek, H.J. (June 1976). "Special Tutorial: Introduction to LSI Microprocessor Developments".Computer.9 (Computer). IEEE: 37.doi:10.1109/C-M.1976.218612.S2CID 11184882.
  4. ^Proof of "micro" as a once-common term:
    (i) Direct reference: Graham Kibble-White,"Stand by for a Data-Blast", Off the Telly. Article written December 2005, retrieved 2006-12-15.
    (ii) Usage in the titles ofChristopher Evans' books"The Mighty Micro" (ISBN 0-340-25975-2) and"The Making of the Micro" (ISBN 0-575-02913-7). Other books include Usborne's"Understanding the Micro" (ISBN 0-86020-637-8), a children's guide to microcomputers.
  5. ^Asimov, Isaac (July 1956). "The Dying Night".The Magazine of Fantasy and Science Fiction.
  6. ^Ceruzzi, Paul (2012).Computing: a concise history. Cambridge, MA: MIT Press. p. 105.ISBN 9780262517676.
  7. ^"microcomputer". OED Online. December 2013. Oxford University Press. 15 February 2014.
  8. ^"personal computer". OED Online. December 2013. Oxford University Press. 15 February 2014
  9. ^"The Museum of HP Calculators".
  10. ^"Powerful Computing Genie"(PDF). Hewlett Packard.Archived(PDF) from the original on 2006-03-12. Retrieved2012-08-30.
  11. ^"Restoring the Balance Between Analysis and Computation"(PDF).Archived(PDF) from the original on 2007-06-21. Retrieved2012-08-30.
  12. ^"History of the 9100A desktop calculator, 1968".HP virtual museum. Retrieved2019-07-19.
  13. ^"MicroprocessorHistory". Computermuseum.li. 1971-11-15. Archived fromthe original on 2015-09-23. Retrieved2012-08-30.
  14. ^"Kenbak-1".The Vintage Computer. Archived fromthe original on 2011-01-22. Retrieved2006-08-14.
  15. ^"Digibarn Stories: Bill Pentz and (Earliest) History of the Microcomputer (August 2008)".DigiBarn Computer Museum. August–November 2008. Retrieved2012-08-30.
  16. ^Terdiman, Daniel (2010-01-08)."Inside the world's long-lost first microcomputer".CNET. Retrieved2012-08-30.
  17. ^"SMP80/X series-Computer Museum".
  18. ^"16-bit timeline". 19 November 1997.
  19. ^"Paper Tape Readers Work With IMP Micros".Computerworld. 23 Oct 1974. p. 28.
  20. ^"Upward Compatible Software and Downward Compatible Price".Computerworld. 10 Dec 1975. p. 49.
  21. ^Hawkins, William J. (December 1983)."Computer Adventures".Popular Science.
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