A computer is a machine that can be programmed to automatically carry out sequences
of arithmetic or logical operations (computation). Modern digital electronic computers can
perform generic sets of operations known as programs, which enable computers to
perform a wide range of tasks. The term computer system may refer to a nominally
complete computer that includes the hardware, operating system, software,
and peripheral equipment needed and used for full operation; or to a group of computers
that are linked and function together, such as a computer network or computer cluster.
A broad range of industrial and consumer products use computers as control systems,
including simple special-purpose devices like microwave ovens and remote controls, and
factory devices like industrial robots. Computers are at the core of general-purpose
devices such as personal computers and mobile devices such as smartphones.
Computers power the Internet, which links billions of computers and users.
Early computers were meant to be used only for calculations. Simple manual instruments
like the abacus have aided people in doing calculations since ancient times. Early in
the Industrial Revolution, some mechanical devices were built to automate long, tedious
tasks, such as guiding patterns for looms. More sophisticated electrical machines did
specialized analog calculations in the early 20th century. The first digital electronic
calculating machines were developed during World War II, both electromechanical and
using thermionic valves. The first semiconductor transistors in the late 1940s were
followed by the silicon-based MOSFET (MOS transistor) and monolithic integrated
circuit chip technologies in the late 1950s, leading to the microprocessor and
the microcomputer revolution in the 1970s. The speed, power, and versatility of computers
have been increasing dramatically ever since then, with transistor counts increasing at a
rapid pace (Moore's law noted that counts doubled every two years), leading to the Digital
Revolution during the late 20th and early 21st centuries.
Conventionally, a modern computer consists of at least one processing element, typically
a central processing unit (CPU) in the form of a microprocessor, together with some type
of computer memory, typically semiconductor memory chips. The processing element
carries out arithmetic and logical operations, and a sequencing and control unit can
change the order of operations in response to stored information. Peripheral devices
include input devices (keyboards, mice, joysticks, etc.), output devices (monitors, printers,
etc.), and input/output devices that perform both functions (e.g. touchscreens). Peripheral
devices allow information to be retrieved from an external source, and they enable the
results of operations to be saved and retrieved.
Etymology
A human computer, with microscope and
calculator, 1952
It was not until the mid-20th century that the word acquired its modern definition;
according to the Oxford English Dictionary, the first known use of the word computer was in
a different sense, in a 1613 book called The Yong Mans Gleanings by the English
writer Richard Brathwait: "I haue [sic] read the truest computer of Times, and the best
Arithmetician that euer [sic] breathed, and he reduceth thy dayes into a short number." This
usage of the term referred to a human computer, a person who carried out calculations
or computations. The word continued to have the same meaning until the middle of the
20th century. During the latter part of this period, women were often hired as computers
because they could be paid less than their male counterparts.[1] By 1943, most human
computers were women.[2]
The Online Etymology Dictionary gives the first attested use of computer in the 1640s,
meaning 'one who calculates'; this is an "agent noun from compute (v.)". The Online
Etymology Dictionary states that the use of the term to mean "'calculating machine' (of any
type) is from 1897." The Online Etymology Dictionary indicates that the "modern use" of the
term, to mean 'programmable digital electronic computer' dates from "1945 under this
name; [in a] theoretical [sense] from 1937, as Turing machine".[3] The name has remained,
although modern computers are capable of many higher-level functions.
