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A microcomputer is a small, relatively inexpensive
computer A computer is a machine that can be programmed to carry out sequences of arithmetic or logical operations ( computation) automatically. Modern digital electronic computers can perform generic sets of operations known as programs. These prog ...
having a
central processing unit A central processing unit (CPU), also called a central processor, main processor or just processor, is the electronic circuitry that executes instructions comprising a computer program. The CPU performs basic arithmetic, logic, controlling, a ...
(CPU) made out of a
microprocessor A microprocessor is a computer processor where the data processing logic and control is included on a single integrated circuit, or a small number of integrated circuits. The microprocessor contains the arithmetic, logic, and control circ ...
. The computer also includes
memory Memory is the faculty of the mind by which data or information is encoded, stored, and retrieved when needed. It is the retention of information over time for the purpose of influencing future action. If past events could not be remember ...
and
input/output In computing, input/output (I/O, or informally io or IO) is the communication between an information processing system, such as a computer, and the outside world, possibly a human or another information processing system. Inputs are the signals ...
(I/O) circuitry together mounted on a
printed circuit board A printed circuit board (PCB; also printed wiring board or PWB) is a medium used in electrical and electronic engineering to connect electronic components to one another in a controlled manner. It takes the form of a laminated sandwich str ...
(PCB). 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 Keyboard may refer to: Text input * Keyboard, part of a typewriter * Computer keyboard ** Keyboard layout, the software control of computer keyboards and their mapping ** Keyboard technology, computer keyboard hardware and firmware Music * Mu ...
and screen for input and output) are also
personal computer A personal computer (PC) is a multi-purpose microcomputer whose size, capabilities, and price make it feasible for individual use. Personal computers are intended to be operated directly by an end user, rather than by a computer expert or te ...
s (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 an
IBM PC compatible IBM PC compatible computers are similar to the original IBM PC, XT, and AT, all from computer giant IBM, that are able to use the same software and expansion cards. Such computers were referred to as PC clones, IBM clones or IBM PC clones ...
machine. The abbreviation ''micro'' was common during the 1970s and 1980s,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' book
"The Mighty Micro"
() an
"The Making of the Micro"
(). Other books include Usborne'
"Understanding the Micro"
(), a children's guide to microcomputers.
but has since fallen out of common usage.


Origins

The term ''microcomputer'' came into popular use after the introduction of the minicomputer, although
Isaac Asimov yi, יצחק אזימאװ , birth_date = , birth_place = Petrovichi, Russian SFSR , spouse = , relatives = , children = 2 , death_date = , death_place = Manhattan, New York City, U.S. , nationality = Russian (1920–1922)Soviet (192 ...
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). Most notably, the microcomputer replaced the many separate components that made up the minicomputer's CPU with one integrated microprocessor chip. In 1973, the French Institut National de la Recherche Agronomique (INRA) was looking for a computer able to measure agricultural hygrometry. 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, the Micral 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 the Altair 8800 were often sold as kits to be assembled by the user, and came with as little as 256
byte The byte is a unit of digital information that most commonly consists of eight bits. 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 uni ...
s of RAM, and no
input/output In computing, input/output (I/O, or informally io or IO) is the communication between an information processing system, such as a computer, and the outside world, possibly a human or another information processing system. Inputs are the signals ...
devices other than indicator lights and switches, useful as a proof of concept to demonstrate what such a simple device could do. As microprocessors and
semiconductor memory Semiconductor memory is a digital electronic semiconductor device used for digital data storage, such as computer memory. It typically refers to devices in which data is stored within metal–oxide–semiconductor (MOS) memory cells on a si ...
became less expensive, microcomputers grew cheaper and easier to use. * Increasingly inexpensive logic chips such as the 7400 series allowed cheap dedicated circuitry for improved user interfaces such as
keyboard Keyboard may refer to: Text input * Keyboard, part of a typewriter * Computer keyboard ** Keyboard layout, the software control of computer keyboards and their mapping ** Keyboard technology, computer keyboard hardware and firmware Music * Mu ...
input, instead of simply a row of switches to toggle bits one at a time. * Use of audio cassettes for inexpensive data storage replaced manual re-entry of a program every time the device was powered on. * Large cheap arrays of silicon logic gates in the form of
read-only memory Read-only memory (ROM) is a type of non-volatile memory used in computers and other electronic devices. Data stored in ROM cannot be electronically modified after the manufacture of the memory device. Read-only memory is useful for storing ...
and EPROMs allowed utility programs and self-
booting In computing, booting is the process of starting a computer as initiated via Computer hardware, hardware such as a button or by a software command. After it is switched on, a computer's central processing unit (CPU) has no software in its ma ...
kernels to be stored within microcomputers. These stored programs could automatically load further more complex software from external storage devices without user intervention, to form an inexpensive
turnkey system A turnkey, a turnkey project, or a turnkey operation (also spelled turn-key) is a type of project that is constructed so that it can be sold to any buyer as a completed product. This is contrasted with build to order, where the constructor builds ...
that does not require a computer expert to understand or to use the device. *
Random-access memory Random-access memory (RAM; ) is a form of computer memory that can be read and changed in any order, typically used to store working data and machine code. A random-access memory device allows data items to be read or written in almost the ...
became cheap enough to afford dedicating approximately 1–2 kilobytes of memory to a video display controller frame buffer, for a 40x25 or 80x25 text display or blocky color graphics on a common household
television Television, sometimes shortened to TV, is a telecommunication medium for transmitting moving images and sound. The term can refer to a television set, or the medium of television transmission. Television is a mass medium for advertising, ...
. This replaced the slow, complex, and expensive
teletypewriter A teleprinter (teletypewriter, teletype or TTY) is an electromechanical device that can be used to send and receive typed messages through various communications channels, in both point-to-point and point-to-multipoint configurations. Initi ...
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 as Cromemco, 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 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 The S-100 bus or Altair bus, IEEE 696-1983 ''(withdrawn)'', is an early computer bus designed in 1974 as a part of the Altair 8800. The bus was the first industry standard expansion bus for the microcomputer industry. computers, consisting of p ...
, an
8-bit In computer architecture, 8-bit integers or other data units are those that are 8 bits wide (1 octet). Also, 8-bit central processing unit (CPU) and arithmetic logic unit (ALU) architectures are those that are based on registers or data buses ...
processor such as an Intel 8080 or Zilog Z80, and either
CP/M CP/M, originally standing for Control Program/Monitor and later Control Program for Microcomputers, is a mass-market operating system created in 1974 for Intel 8080/ 85-based microcomputers by Gary Kildall of Digital Research, Inc. Initi ...
or MP/M operating system. The increasing availability and power of desktop computers for personal use attracted the attention of more software developers. As the industry matured, the market for
personal computer A personal computer (PC) is a multi-purpose microcomputer whose size, capabilities, and price make it feasible for individual use. Personal computers are intended to be operated directly by an end user, rather than by a computer expert or te ...
s standardized around
IBM PC compatible IBM PC compatible computers are similar to the original IBM PC, XT, and AT, all from computer giant IBM, that are able to use the same software and expansion cards. Such computers were referred to as PC clones, IBM clones or IBM PC clones ...
s running DOS, and later
Windows Windows is a group of several proprietary graphical operating system families developed and marketed by Microsoft. Each family caters to a certain sector of the computing industry. For example, Windows NT for consumers, Windows Server for se ...
. Modern desktop computers, video game consoles,
laptop A laptop, laptop computer, or notebook computer is a small, portable personal computer (PC) with a screen and alphanumeric keyboard. Laptops typically have a clam shell form factor with the screen mounted on the inside of the upper li ...
s, tablet PCs, and many types of
handheld device A mobile device (or handheld computer) is a computer small enough to hold and operate in the hand. Mobile devices typically have a flat LCD or OLED screen, a touchscreen interface, and digital or physical buttons. They may also have a physic ...
s, including
mobile phone A mobile phone, cellular phone, cell phone, cellphone, handphone, hand phone or pocket phone, sometimes shortened to simply mobile, cell, or just phone, is a portable telephone that can make and receive calls over a radio frequency link whi ...
s, pocket
calculator An electronic calculator is typically a portable electronic device used to perform calculations, ranging from basic arithmetic to complex mathematics. The first solid-state electronic calculator was created in the early 1960s. Pocket-sized ...
s, and industrial
embedded system An embedded system is a computer system—a combination of a computer processor, computer memory, and input/output peripheral devices—that has a dedicated function within a larger mechanical or electronic system. It is ''embedded ...
s, may all be considered examples of microcomputers according to the definition given above.


Colloquial use of the term

By the early 2000s, everyday use of the expression "microcomputer" (and in particular "micro") declined significantly from its peak in the mid-1980s. The term is most commonly associated with the most popular all-in-one
8-bit In computer architecture, 8-bit integers or other data units are those that are 8 bits wide (1 octet). Also, 8-bit central processing unit (CPU) and arithmetic logic unit (ALU) architectures are those that are based on registers or data buses ...
home computers (such as the
Apple II The Apple II (stylized as ) is an 8-bit home computer and one of the world's first highly successful mass-produced microcomputer products. It was designed primarily by Steve Wozniak; Jerry Manock developed the design of Apple II's foam-m ...
, ZX Spectrum, Commodore 64, BBC Micro, and
TRS-80 The TRS-80 Micro Computer System (TRS-80, later renamed the Model I to distinguish it from successors) is a desktop microcomputer launched in 1977 and sold by Tandy Corporation through their Radio Shack stores. The name is an abbreviation of ' ...
) and small-business
CP/M CP/M, originally standing for Control Program/Monitor and later Control Program for Microcomputers, is a mass-market operating system created in 1974 for Intel 8080/ 85-based microcomputers by Gary Kildall of Digital Research, Inc. Initi ...
-based microcomputers. In colloquial usage, "microcomputer" has been largely supplanted by the term "
personal computer A personal computer (PC) is a multi-purpose microcomputer whose size, capabilities, and price make it feasible for individual use. Personal computers are intended to be operated directly by an end user, rather than by a computer expert or te ...
" 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. IBM first promoted the term "personal computer" to differentiate the IBM PC from
CP/M CP/M, originally standing for Control Program/Monitor and later Control Program for Microcomputers, is a mass-market operating system created in 1974 for Intel 8080/ 85-based microcomputers by Gary Kildall of Digital Research, Inc. Initi ...
-based microcomputers likewise targeted at the small-business market, and also IBM's own mainframes and minicomputers. However, following its release, the IBM PC itself was widely imitated, as well as the term. The component parts were commonly available to producers and the BIOS was reverse engineered through
cleanroom design Clean-room design (also known as the Chinese wall technique) is the method of copying a design by reverse engineering and then recreating it without infringing any of the copyrights associated with the original design. Clean-room design is usef ...
techniques.
IBM PC compatible IBM PC compatible computers are similar to the original IBM PC, XT, and AT, all from computer giant IBM, that are able to use the same software and expansion cards. Such computers were referred to as PC clones, IBM clones or IBM PC clones ...
"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

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 A power supply is an electrical device that supplies electric power to an electrical load. The main purpose of a power supply is to convert electric current from a source to the correct voltage, current, and frequency to power the load. As ...
unit, a keyboard and various input/output devices used to convey information to and from a human operator ( printers,
monitors Monitor or monitor may refer to: Places * Monitor, Alberta * Monitor, Indiana, town in the United States * Monitor, Kentucky * Monitor, Oregon, unincorporated community in the United States * Monitor, Washington * Monitor, Logan County, West ...
, 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
supercomputer A supercomputer is a computer with a high level of performance as compared to a general-purpose computer. The performance of a supercomputer is commonly measured in floating-point operations per second ( FLOPS) instead of million instructio ...
s take up large
cabinet Cabinet or The Cabinet may refer to: Furniture * Cabinetry, a box-shaped piece of furniture with doors and/or drawers * Display cabinet, a piece of furniture with one or more transparent glass sheets or transparent polycarbonate sheets * Filin ...
s 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 Computer data storage is a technology consisting of computer components and recording media that are used to retain digital data. It is a core function and fundamental component of computers. The central processing unit (CPU) of a compute ...
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 A floppy disk or floppy diskette (casually referred to as a floppy, or a diskette) is an obsolescent type of disk storage composed of a thin and flexible disk of a magnetic storage medium in a square or nearly square plastic enclosure lined ...
and
hard disk A hard disk drive (HDD), hard disk, hard drive, or fixed disk is an electro-mechanical data storage device that stores and retrieves digital data using magnetic storage with one or more rigid rapidly rotating platters coated with magn ...
drives) were built into the microcomputer case.


History


TTL precursors

Although they did not contain any microprocessors, but were built around transistor-transistor logic (TTL),
Hewlett-Packard The Hewlett-Packard Company, commonly shortened to Hewlett-Packard ( ) or HP, was an American multinational information technology company headquartered in Palo Alto, California. HP developed and provided a wide variety of hardware components ...
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 computer programming, assembly language (or assembler language, or symbolic machine code), often referred to simply as Assembly and commonly abbreviated as ASM or asm, is any low-level programming language with a very strong correspondence b ...
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. The
HP 9100A HP may refer to: Businesses and organisations * HP Inc., an American technology company ** Hewlett-Packard, the predecessor to HP Inc. * HP Foods ** HP Sauce, formerly made by HP Foods * Handley Page, an aircraft company * Hindustan Petroleum ...
was referred to as a
personal computer A personal computer (PC) is a multi-purpose microcomputer whose size, capabilities, and price make it feasible for individual use. Personal computers are intended to be operated directly by an end user, rather than by a computer expert or te ...
in an advertisement in a 1968
Science Science is a systematic endeavor that builds and organizes knowledge in the form of testable explanations and predictions about the universe. Science may be as old as the human species, and some of the earliest archeological evidence ...
magazine, but that advertisement was quickly dropped. 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. 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. Another early system, the
Kenbak-1 The Kenbak-1 is considered by the Computer History Museum, the Computer Museum of America and the American Computer Museum to be the world's first "personal computer", invented by John Blankenbaker (born 1929) of Kenbak Corporation in 1970, and fi ...
, was released in 1971. Like the Datapoint 2200, it used small-scale integrated
transistor–transistor logic Transistor–transistor logic (TTL) is a logic family built from bipolar junction transistors. Its name signifies that transistors perform both the logic function (the first "transistor") and the amplifying function (the second "transistor"), as o ...
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.


Early microcomputers

In late 1972, a French team headed by François Gernelle within a small company, Réalisations & Etudes Electroniques (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, 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 Component-based software engineering (CBSE), also called component-based development (CBD), is a branch of software engineering that emphasizes the separation of concerns with respect to the wide-ranging functionality available throughout a give ...
: 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. 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. 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. The period from about 1971 to 1976 is sometimes called the first generation of microcomputers. Many companies such as DEC,
National Semiconductor National Semiconductor was an American semiconductor manufacturer which specialized in analog devices and subsystems, formerly with headquarters in Santa Clara, California. The company produced power management integrated circuits, display dr ...
,
Texas Instruments Texas Instruments Incorporated (TI) is an American technology company headquartered in Dallas, Texas, that designs and manufactures semiconductors and various integrated circuits, which it sells to electronics designers and manufacturers globa ...
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. 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 A personal computer (PC) is a multi-purpose microcomputer whose size, capabilities, and price make it feasible for individual use. Personal computers are intended to be operated directly by an end user, rather than by a computer expert or te ...
hardware and software companies, such as
Microsoft Microsoft Corporation is an American multinational technology corporation producing computer software, consumer electronics, personal computers, and related services headquartered at the Microsoft Redmond campus located in Redmond, Washi ...
and
Apple Computer Apple Inc. is an American multinational technology company headquartered in Cupertino, California, United States. Apple is the largest technology company by revenue (totaling in 2021) and, as of June 2022, is the world's biggest company ...
. 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 A spreadsheet is a computer application for computation, organization, analysis and storage of data in tabular form. Spreadsheets were developed as computerized analogs of paper accounting worksheets. The program operates on data entered in ...
(initially for the
Apple II The Apple II (stylized as ) is an 8-bit home computer and one of the world's first highly successful mass-produced microcomputer products. It was designed primarily by Steve Wozniak; Jerry Manock developed the design of Apple II's foam-m ...
) 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 A personal computer (PC) is a multi-purpose microcomputer whose size, capabilities, and price make it feasible for individual use. Personal computers are intended to be operated directly by an end user, rather than by a computer expert or te ...
became generally used for microcomputers compatible with the IBM PC architecture ( PC compatible).


See also

*
History of computing hardware (1960s-present) History (derived ) is the systematic study and the documentation of the human activity. The time period of event before the invention of writing systems is considered prehistory. "History" is an umbrella term comprising past events as wel ...
*
Lists of microcomputers For an overview of microcomputers of different kinds, see the following lists of microcomputers: *List of early microcomputers * List of home computers *List of home computers by video hardware This is a list of home computers, sorted alphanume ...
* Mainframe computer * Market share of personal computer vendors * Minicomputer *
Personal computer A personal computer (PC) is a multi-purpose microcomputer whose size, capabilities, and price make it feasible for individual use. Personal computers are intended to be operated directly by an end user, rather than by a computer expert or te ...
* SFF computer *
Supercomputer A supercomputer is a computer with a high level of performance as compared to a general-purpose computer. The performance of a supercomputer is commonly measured in floating-point operations per second ( FLOPS) instead of million instructio ...


Notes and references

{{Authority control *Microcomputer Computers