Microcomputer

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The Commodore 64 was one of the most popular microcomputers of its era, and is the best-selling model of home computer of all time. Commodore-64-Computer-FL.jpg
The Commodore 64 was one of the most popular microcomputers of its era, and is the best-selling model of home computer of all time.

A microcomputer is a small, relatively inexpensive computer with a microprocessor as its central processing unit (CPU). [2] It includes a microprocessor, memory, and minimal input/output (I/O) circuitry mounted on a single printed circuit board. [3] Microcomputers became popular in the 1970s and 1980s with the advent of increasingly powerful microprocessors. The predecessors to these computers, mainframes and minicomputers, were comparatively much larger and more expensive (though indeed present-day mainframes such as the IBM System z machines use one or more custom microprocessors as their CPUs). Many microcomputers (when equipped with a keyboard and screen for input and output) are also personal computers (in the generic sense). [4]

A computer is a device that can be instructed to carry out sequences of arithmetic or logical operations automatically via computer programming. Modern computers have the ability to follow generalized sets of operations, called programs. These programs enable computers to perform an extremely wide range of tasks. A "complete" computer including the hardware, the operating system, and peripheral equipment required and used for "full" operation can be referred to as a computer system. This term may as well be used for a group of computers that are connected and work together, in particular a computer network or computer cluster.

Microprocessor computer processor contained on an integrated-circuit chip

A microprocessor is a computer processor that incorporates the functions of a central processing unit on a single integrated circuit (IC), or at most a few integrated circuits. The microprocessor is a multipurpose, clock driven, register based, digital integrated circuit that accepts binary data as input, processes it according to instructions stored in its memory, and provides results as output. Microprocessors contain both combinational logic and sequential digital logic. Microprocessors operate on numbers and symbols represented in the binary number system.

Central processing unit electronic circuitry within a computer that carries out the instructions of a computer program by performing the basic arithmetic, logical, control and input/output (I/O) operations specified by the instructions

A central processing unit (CPU), also called a central processor or main processor, is the electronic circuitry within a computer that carries out the instructions of a computer program by performing the basic arithmetic, logic, controlling, and input/output (I/O) operations specified by the instructions. The computer industry has used the term "central processing unit" at least since the early 1960s. Traditionally, the term "CPU" refers to a processor, more specifically to its processing unit and control unit (CU), distinguishing these core elements of a computer from external components such as main memory and I/O circuitry.

Contents

The abbreviation micro was common during the 1970s and 1980s, [5] but has now fallen out of common usage.

Origins

The term microcomputer came into popular use after the introduction of the minicomputer, although Isaac Asimov used the term in his short story "The Dying Night" as early as 1956 (published in The Magazine of Fantasy and Science Fiction in July that year). [6] Most notably, the microcomputer replaced the many separate components that made up the minicomputer's CPU with one integrated microprocessor chip.

Minicomputer class of smaller computers

A minicomputer, or colloquially mini, is a class of smaller computers that was developed in the mid-1960s and sold for much less than mainframe and mid-size computers from IBM and its direct competitors. In a 1970 survey, The New York Times suggested a consensus definition of a minicomputer as a machine costing less than US$25,000, with an input-output device such as a teleprinter and at least four thousand words of memory, that is capable of running programs in a higher level language, such as Fortran or BASIC. The class formed a distinct group with its own software architectures and operating systems. Minis were designed for control, instrumentation, human interaction, and communication switching as distinct from calculation and record keeping. Many were sold indirectly to original equipment manufacturers (OEMs) for final end use application. During the two decade lifetime of the minicomputer class (1965–1985), almost 100 companies formed and only a half dozen remained.

Isaac Asimov American science-fiction and non-fiction writer

Isaac Asimov was an American writer and professor of biochemistry at Boston University. He was known for his works of science fiction and popular science. Asimov was a prolific writer who wrote or edited more than 500 books and an estimated 90,000 letters and postcards. His books have been published in 9 of the 10 major categories of the Dewey Decimal Classification.

"The Dying Night" is a science fiction short story by American writer Isaac Asimov. The story first appeared in the July 1956 issue of The Magazine of Fantasy & Science Fiction, and was reprinted in the collections Nine Tomorrows (1959), Asimov's Mysteries (1968), and The Best of Isaac Asimov (1973). "The Dying Night" is Asimov's third Wendell Urth story.

The French developers of the Micral N (1973) 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 USA, the earliest models such as the Altair 8800 were often sold as kits to be assembled by the user, and came with as little as 256 bytes of RAM, and no input/output devices other than indicator lights and switches, useful as a proof of concept to demonstrate what such a simple device could do. [7] However, as microprocessors and semiconductor memory became less expensive, microcomputers in turn grew cheaper and easier to use:

Micral Computer by R2E

Micral is a series of microcomputers produced by the French company Réalisation d'Études Électroniques (R2E), beginning with the Micral N in early 1973.

Altair 8800 microcomputer designed in 1975

The Altair 8800 is a microcomputer designed in 1974 by MITS and based on the Intel 8080 CPU. Interest grew quickly after it was featured on the cover of the January 1975 issue of Popular Electronics, and was sold by mail order through advertisements there, in Radio-Electronics, and in other hobbyist magazines. The designers hoped to sell a few hundred build-it-yourself kits to hobbyists, and were surprised when they sold thousands in the first month. The Altair also appealed to individuals and businesses that just wanted a computer and purchased the assembled version. The Altair is widely recognized as the spark that ignited the microcomputer revolution as the first commercially successful personal computer. The computer bus designed for the Altair was to become a de facto standard in the form of the S-100 bus, and the first programming language for the machine was Microsoft's founding product, Altair BASIC.

The byte is a unit of digital information that most commonly consists of eight bits, representing a binary number. Historically, the byte was the number of bits used to encode a single character of text in a computer and for this reason it is the smallest addressable unit of memory in many computer architectures.

User interface means by which a user interacts with and controls a machine

The user interface (UI), in the industrial design field of human–computer interaction, is the space where interactions between humans and machines occur. The goal of this interaction is to allow effective operation and control of the machine from the human end, whilst the machine simultaneously feeds back information that aids the operators' decision-making process. Examples of this broad concept of user interfaces include the interactive aspects of computer operating systems, hand tools, heavy machinery operator controls, and process controls. The design considerations applicable when creating user interfaces are related to or involve such disciplines as ergonomics and psychology.

Read-only memory non-volatile memory used in computers and other electronic devices; class of storage medium used in computers and other electronic devices

Read-only memory (ROM) is a type of non-volatile memory used in computers and other electronic devices. Data stored in ROM can only be modified slowly, with difficulty, or not at all, so it is mainly used to store firmware or application software in plug-in cartridges.

An EPROM, or erasable programmable read-only memory, is a type of memory chip that retains its data when its power supply is switched off. Computer memory that can retrieve stored data after a power supply has been turned off and back on is called non-volatile. It is an array of floating-gate transistors individually programmed by an electronic device that supplies higher voltages than those normally used in digital circuits. Once programmed, an EPROM can be erased by exposing it to strong ultraviolet light source. EPROMs are easily recognizable by the transparent fused quartz window in the top of the package, through which the silicon chip is visible, and which permits exposure to ultraviolet light during erasing.

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 as Cromemco, Processor Technology, IMSAI, North Star Computers, Southwest Technical Products Corporation, Ohio Scientific, Altos Computer Systems, Morrow Designs and others produced systems designed either for a resourceful end user or consulting firm 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 or time-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 an S100 bus, an 8-bit processor such as an Intel 8080 or Zilog Z80, and either CP/M or MP/M operating system. The increasing availability and power of desktop computers for personal use attracted the attention of more software developers. In time, and as the industry matured, the market for personal computers standardized around IBM PC compatibles running DOS, and later Windows. Modern desktop computers, video game consoles, laptops, tablet PCs, and many types of handheld devices, including mobile phones, pocket calculators, and industrial embedded systems, may all be considered examples of microcomputers according to the definition given above.

Cromemco was a Mountain View, California microcomputer company known for its high-end Z80-based S-100 bus computers and peripherals in the early days of the personal computer revolution.

Processor Technology Corporation was a personal computer company founded in April 1975 by Gary Ingram and Bob Marsh in Berkeley, California. Their first product was a 4K byte RAM board that was compatible with the MITS Altair 8800 computer but more reliable than the MITS board. This was followed by a series of memory and I/O boards including a video display module.

North Star Computers Inc. was an American computer company based in Berkeley, California existing between June 1976 and 1984. Originally a mail order business for IMSAI computers, it soon developed into a major player in the early microcomputer market, becoming first known for their low-cost floppy disk system for S-100 bus machines, and later for their own S-100 bus computers running either the CP/M operating system or North Star's own proprietary operating system, NSDOS. North Star BASIC was a common dialect of the popular BASIC programming language. They later expanded their lineup with dual-CPU machines able to run MS-DOS, and a server version running either DOS or Novell NetWare.

Colloquial use of the term

Everyday use of the expression "microcomputer" (and in particular the "micro" abbreviation) has declined significantly from the mid-1980s and has declined in commonplace usage since 2000. [8] The term is most commonly associated with the first wave of all-in-one 8-bit home computers and small business microcomputers (such as the Apple II, Commodore 64, BBC Micro, and TRS 80). Although, or perhaps because, an increasingly diverse range of modern microprocessor-based devices fit the definition of "microcomputer", they are no longer referred to as such in everyday speech.

In common 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. [9] IBM first promoted the term "personal computer" to differentiate themselves from other microcomputers, often called "home computers", 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 the BIOS was reverse engineered through cleanroom 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 DOS or (nowadays) Windows-compatible computer.

Since the advent of microcontrollers (monolithic integrated circuits containing RAM, ROM and CPU all onboard), the term "micro" is more commonly used to refer to that meaning.[ citation needed ]

Description

Monitors, keyboards and other devices for input and output may be integrated or separate. Computer memory in the form of RAM, and at least one other less volatile, memory storage device are usually combined with the CPU on a system bus in one unit. Other devices that make up a complete microcomputer system include batteries, a power 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 like minicomputers, mainframes, and supercomputers take up large cabinets or even dedicated rooms.

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

History

A collection of early microcomputers, including a Processor Technology SOL-20 (top shelf, right), an MITS Altair 8800 (second shelf, left), a TV Typewriter (third shelf, center), and an Apple I in the case at far right. Early Personal Computers.jpg
A collection of early microcomputers, including a Processor Technology SOL-20 (top shelf, right), an MITS Altair 8800 (second shelf, left), a TV Typewriter (third shelf, center), and an Apple I in the case at far right.

TTL precursors

Although they did not contain any microprocessors, but were built around transistor-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 resembled assembly language in many ways. Later models incrementally added more features, including the BASIC programming language (HP 9830A in 1971). Some models had tape storage and small printers. However, displays were limited to one line at a time. [10] The HP 9100A was referred to as a personal computer in an advertisement in a 1968 Science magazine, [11] but that advertisement was quickly dropped. [12] 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. HP virtual museum

The Datapoint 2200, made by CTC in 1970, was also comparable to microcomputers. While it contains no microprocessor, the instruction set of its custom TTL processor was the basis of the instruction set for the Intel 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, the Kenbak-1, was released in 1971. Like the Datapoint 2200, it used discrete transistor–transistor logic instead of a microprocessor, but it functioned like a microcomputer in some ways. It was marketed as an educational and hobbyist tool, but it was not a commercial success; production ceased shortly after introduction. [14]

Early microcomputers

In late 1972, a French team headed by François Gernelle within a small company, Réalisations & Etudes Electroniqes (R2E), developed and patented a computer based on a microprocessor – the Intel 8008 8-bit microprocessor. This Micral-N was marketed in early 1973 as a "Micro-ordinateur" or microcomputer, mainly for scientific and process-control applications. About a hundred Micral-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 the Zilog Z80 as main processor.

In late 1972, a Sacramento State University team led by Bill Pentz built the Sac State 8008 computer, [15] 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 and software 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. [16]

In early 1973, Sord Computer Corporation (now Toshiba Personal Computer System Corporation) completed the SMP80/08, which used the Intel 8008 microprocessor. The SMP80/08, however, did not have a commercial release. After the first general-purpose microprocessor, the Intel 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 MITS Altair 8800 (1975) was arguably the most famous. Most of these simple, early microcomputers were sold as electronic kits—bags full of loose components which the buyer had to solder together before the system could be used.

Microcomputer module LSI-11/2 PDP-11-M7270.jpg
Microcomputer module LSI-11/2

The period from about 1971 to 1976 is sometimes called the first generation of microcomputers. Many companies such as DEC, [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, the Processor Technology SOL-20 was designed, which consisted of one board which included all the parts of the computer system. The SOL-20 had built-in EPROM software which eliminated the need for rows of switches and lights. The MITS Altair just mentioned played an instrumental role in sparking significant hobbyist interest, which itself eventually led to the founding and success of many well-known personal computer hardware and software companies, such as Microsoft and Apple Computer. Although the Altair itself was only a mild commercial success, it helped spark a huge industry.

Home computers

By 1977, the introduction of the second generation, known as home computers, made microcomputers 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. The BASIC language, which was easier to learn and use than raw machine language, became a standard feature. These features were already common in minicomputers, with which many hobbyists and early produces were familiar.

In 1979, the launch of the VisiCalc spreadsheet (initially for the Apple II) first turned the microcomputer from a hobby for computer enthusiasts into a business tool. After the 1981 release by IBM of its IBM PC, the term personal computer became generally used for microcomputers compatible with the IBM PC architecture (PC compatible).

See also

Notes and references

  1. Kahney, Leander (2003-09-09). "Grandiose Price for a Modest PC". Wired. Lycos. Retrieved 2006-10-25.
  2. "Microcomputer". dictionary.com.
  3. A.O., Williman; Jelinek, H.J. (June 1976). "Special Tutorial: Introduction to LSI Microprocessor Developments" (Computer). IEEE: 37. doi:10.1109/C-M.1976.218612. ISSN   0018-9162.
  4. 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 an IBM PC compatible machine.
  5. 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 of Christopher 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.
  6. Asimov, Isaac (July 1956). "The Dying Night". The Magazine of Fantasy and Science Fiction.
  7. Ceruzzi, Paul (2012). Computing: a concise history. Cambridge, MA: MIT Press. p. 105. ISBN   9780262517676.
  8. "microcomputer". OED Online. December 2013. Oxford University Press. 15 February 2014.
  9. "personal computer". OED Online. December 2013. Oxford University Press. 15 February 2014
  10. "The Museum of HP Calculators".
  11. "Powerful Computing Genie" (PDF). Hewlett Packard. Retrieved 2012-08-30.
  12. "Restoring the Balance Between Analysis and Computation" (PDF). Retrieved 2012-08-30.
  13. "MicroprocessorHistory". Computermuseum.li. 1971-11-15. Archived from the original on 2015-09-23. Retrieved 2012-08-30.
  14. "Kenbak-1". The Vintage Computer.
  15. "Digibarn Stories: Bill Pentz and (Earliest) History of the Microcomputer (August 2008)". Digibarn.com. Retrieved 2012-08-30.
  16. Terdiman, Daniel (2010-01-08). "Inside the world's long-lost first microcomputer | Geek Gestalt — CNET News". News.cnet.com. Retrieved 2012-08-30.
  17. http://museum.ipsj.or.jp/en/computer/personal/0086.html
  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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A disk operating system is a computer operating system that can use a disk storage device, such as a floppy disk, hard disk drive, or optical disc. A disk operating system must provide a file system for organizing, reading, and writing files on the storage disk. Strictly speaking, this definition does not apply to current generations of operating systems, such as versions of Microsoft Windows in use, and is more appropriately used only for older generations of operating systems.

Intel 8080 8-bit microprocessor

The Intel 8080 ("eighty-eighty") was the second 8-bit microprocessor designed and manufactured by Intel and was released in April 1974. It is an extended and enhanced variant of the earlier 8008 design, although without binary compatibility. The initial specified clock frequency limit was 2 MHz, and with common instructions using 4, 5, 7, 10, or 11 cycles this meant that it operated at a typical speed of a few hundred thousand instructions per second. A faster variant 8080A-1 became available later with clock frequency limit up to 3.125 MHz.

Intel 8086 16-bit central processing unit

The 8086 is a 16-bit microprocessor chip designed by Intel between early 1976 and June 8, 1978, when it was released. The Intel 8088, released July 1, 1979, is a slightly modified chip with an external 8-bit data bus, and is notable as the processor used in the original IBM PC design, including the widespread version called IBM PC XT.

Motorola 6800

The 6800 is an 8-bit microprocessor designed and first manufactured by Motorola in 1974. The MC6800 microprocessor was part of the M6800 Microcomputer System that also included serial and parallel interface ICs, RAM, ROM and other support chips. A significant design feature was that the M6800 family of ICs required only a single five-volt power supply at a time when most other microprocessors required three voltages. The M6800 Microcomputer System was announced in March 1974 and was in full production by the end of that year.

Zilog Z80 8-bit microprocessor

The Z80 CPU is an 8-bit based microprocessor. It was introduced by Zilog in 1976 as the startup company's first product. The Z80 was conceived by Federico Faggin in late 1974 and developed by him and his then-11 employees at Zilog from early 1975 until March 1976, when the first fully working samples were delivered. With the revenue from the Z80, the company built its own chip factories and grew to over a thousand employees over the following two years.

In computer architecture, 8-bit integers, memory addresses, or other data units are those that are 8 bits wide. Also, 8-bit CPU and ALU architectures are those that are based on registers, address buses, or data buses of that size. 8-bit is also a generation of microcomputers in which 8-bit microprocessors were the norm.

Intel 8008 byte-oriented microprocessor

The Intel 8008 is an early byte-oriented microprocessor designed and manufactured by Intel and introduced in April 1972. It is an 8-bit CPU with an external 14-bit address bus that could address 16 KB of memory. Originally known as the 1201, the chip was commissioned by Computer Terminal Corporation (CTC) to implement an instruction set of their design for their Datapoint 2200 programmable terminal. As the chip was delayed and did not meet CTC's performance goals, the 2200 ended up using CTC's own TTL-based CPU instead. An agreement permitted Intel to market the chip to other customers after Seiko expressed an interest in using it for a calculator.

S-100 bus

The S-100 bus or Altair bus, IEEE696-1983 (withdrawn), is an early computer bus designed in 1974 as a part of the Altair 8800. The S-100 bus was the first industry standard expansion bus for the microcomputer industry. S-100 computers, consisting of processor and peripheral cards, were produced by a number of manufacturers. The S-100 bus formed the basis for homebrew computers whose builders implemented drivers for CP/M and MP/M. These S-100 microcomputers ran the gamut from hobbyist toy to small business workstation and were common in early home computers until the advent of the IBM PC.

The history of computing hardware starting at 1960 is marked by the conversion from vacuum tube to solid-state devices such as the transistor and later the integrated circuit. By 1959 discrete transistors were considered sufficiently reliable and economical that they made further vacuum tube computers uncompetitive. Computer main memory slowly moved away from magnetic core memory devices to solid-state static and dynamic semiconductor memory, which greatly reduced the cost, size and power consumption of computers.

Datapoint 2200

The Datapoint 2200 was a mass-produced programmable terminal, designed by Computer Terminal Corporation (CTC) founders Phil Ray and Gus Roche and announced by CTC in June 1970. It was presented by CTC simply as a versatile and cost-efficient terminal for connecting to a wide variety of mainframes by loading various terminal emulations from tape rather than being hardwired as most contemporary terminals, including their earlier Datapoint 3300. However, enterprising users in the business sector realized that this so-called "programmable terminal" was equipped to perform any task a simple computer could and exploited this fact by using their 2200s as standalone computer systems. Its industrial designer John "Jack" Frassanito has later claimed that Ray and Roche always intended the Datapoint 2200 to be a full-blown personal computer, but that they chose to keep quiet about this so as not to concern investors and others. Also significant is the fact that the terminal's multi-chip CPU (processor) became the basis of the x86 architecture used in the original IBM PC and its descendants.

Influence of the IBM PC on the personal computer market

Following the introduction of the IBM Personal Computer, or IBM PC, many other personal computer architectures became extinct within just a few years.

The history of the personal computer as a mass-market consumer electronic device began with the microcomputer revolution of the 1980s. The 1981 launch of the IBM Personal Computer coined both the term Personal Computer and PC. A personal computer is one intended for interactive individual use,, as opposed to a mainframe computer where the end user's requests are filtered through operating staff, or a time-sharing system in which one large processor is shared by many individuals. After the development of the microprocessor, individual personal computers were low enough in cost that they eventually became affordable consumer goods. Early personal computers – generally called microcomputers – were sold often in electronic kit form and in limited numbers, and were of interest mostly to hobbyists and technicians.

Personal computer computer intended for use by an individual person

A personal computer (PC) is a multi-purpose computer whose size, capabilities, and price make it feasible for individual use. PCs are intended to be operated directly by an end user, rather than by a computer expert or technician. Computer time-sharing models that were typically used with larger, more expensive minicomputer and mainframe systems, to enable them be used by many people at the same time, are not used with PCs.

The microcomputer revolution is a phrase used to describe the rapid advances of microprocessor-based computers from esoteric hobby projects to a commonplace fixture of homes in industrial societies during the 1970s and 1980s. Prior to 1977, the only contact most of the population had with computers was through utility bills, bank and payroll services, or computer-generated junk mail. Within a decade, computers became common consumer goods.

SCELBI was an early model of microcomputer based on the Intel 8008 processor. The company SCELBI Computer Consulting originated in 1973, founded by Nat Wadsworth The SCELBI 8H was marketed in 1974 and was delivered either as an assembled unit or as a kit, with five basic circuit boards and provision for memory expansion to 16,384 words of 8 bits each. The company offered input/output devices including a keyboard, teleprinter interface, alphanumeric oscilloscope interface, and a cassette tape interface for data storage. The basic system only used a front panel with 11 switches and LEDs for input and output.