Microcomputer
microcomputer
[2] is a
computer with a
microprocessor as its
central processin
g unit. Another general characteristic of these computers is that they occupy physically small amounts of space when compared to mainframe and minicomputers. Many microcomputers (when equipped with a keyboard and screen for input and output) are also
personal computers (in the generic sense
The term "Microcomputer" came into popular use after the introduction of the
minicomputer, although
Isaac Asimov used the term microcomputer 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 a single integrated microprocessor
chip.
The earliest models 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. However, as microprocessors and
semiconductor memory became less expensive from the early-to-mid-1970s onwards, microcomputers in turn grew faster and cheaper. This resulted in an explosion in their popularity during the late 1970s and early 1980s.
A large number of computer manufacturers packaged microcomputers for use in small business applications. By 1979, many companies such as
Cromemco,
Northstar,
South West Technical Products,
Ohio Scientific,
Altos,
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 a 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. As time went on and the industry matured, the market for
personal (micro)computers standardized around
IBM PC compatibles running
MS-DOS (and later
Windows).
Modern desktop computers,
video game consoles,
laptop computers,
tablet PCs, and many types of
handheld devices, including
mobile phones and
pocket calculators, as well as industrial
embedded systems, may all be considered examples of microcomputers according to the
definition given above
Colloquial use of the termEveryday use of the expression "microcomputer" (and in particular the "micro" abbreviation) has declined significantly from the mid-
1980s onwards, and is no longer commonplace. It 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 description "
personal computer" or "PC," which describes that it has been designed to be used by one person at a time. 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. Unfortunately for IBM, the microcomputer itself was widely imitated, as well as the term. The component parts were commonly available to manufacturers 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..
[
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 a single 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 a single 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 the user. Bigger computers like
minicomputers,
mainframes, and
supercomputers take up large
cabinets or even a dedicated room.
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 in to the microcomputer case itself
history
Although the
y contained no microprocessors but were built around TTL logic,
Hewlett Packard Calculators as far back as 1968 had various levels of programmability such that they could be called 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 a single line at a time.
[1] The
HP 9100A was referred to as a
personal computer in an advertisement in a 1968
Science magazine
[5] but that advertisement was quickly dropped.
[6] It is suspected[
who?] that HP was reluctant to call them "computers" because it would complicate government procurement and export procedures.[
citation needed]
The
Datapoint 2200, made by
CTC in 1970, is perhaps the best candidate for the title of "first microcomputer". While it contains no microprocessor, it used the
4004 programming
instruction set and its custom TTL logic was the basis 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.
[7]Another early system, the
Kenbak-1, was released in 1971. Like the Datapoint 2200, it used discrete
TTL logic instead of a microprocessor, but functioned like a microcomputer in most ways. It was marketed as an educational and hobbyist tool, but was not a commercial success; production ceased shortly after introduction.
[2]. Another system of note is the
Micral-N, introduced in 1973 by a French company and powered by the 8008; it was the first microcomputer sold all assembled and not as a construction kit.
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 around 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. These machines were for engineering development and hobbyist personal use. In 1975, the
Processor Technology SOL-20 was designed, which consisted of a single board which included all the parts of the computer system. The
SOL-20 had built-in EPROM software which elimated 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.
1977 saw the introduction of the second generation, known as
home computers. These were considerably easier to use than their predecessors, whose operation often demanded thorough familiarity with practical electronics. The ability to connect to a monitor (screen) or TV set allowed for visual manipulation of text and numbers. The
BASIC programming language, which was easier to learn and use than raw machine language, became a standard feature. These features were already common in
minicomputers, which many hobbyists and early manufactures were familiar with.
1979 saw the launch of the
VisiCalc spreadsheet (initially for the
Apple II) that first turned the microcomputer from a hobby for computer enthusiasts into a business tool. After the 1981 release by IBM of their
IBM PC, the term
Personal Computer became generally used for microcomputers compatible with the IBM PC architecture (PC compatibl
