A computer is a
machine which manipulates data according to a list of instructions.
Computers take numerous physical forms. The first devices that resemble
modern computers date to the mid-20th century (around 1940 - 1941), although
the computer concept and various machines similar to computers existed
prior. Early electronic computers were the size of a large room, consuming
as much power as several hundred modern personal computers. |
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[1] Modern computers are based on comparatively
tiny integrated circuits and are millions to billions of times more capable
while occupying a fraction of the space. [2] Today, simple computers may be made
small enough to fit into a wrist watch and be powered from a watch battery.
Personal computers in various forms are icons of the information age and are
what most people think of as "a computer". However, the most common form of
computer in use today is by far the embedded computer. Embedded computers are
small, simple devices that are often used to control other devices — for
example, they may be found in machines ranging from fighter aircraft to
industrial robots, digital cameras, and even children's toys.
The ability to store and execute lists of instructions called programs makes
computers extremely versatile and distinguishes them from calculators. The
Church–Turing thesis is a mathematical statement of this versatility: Any
computer with a certain minimum capability is, in principle, capable of
performing the same tasks that any other computer can perform. Therefore,
computers with capability and complexity ranging from that of a personal digital
assistant to a supercomputer are all able to perform the same computational
tasks given enough time and storage capacity.
It is difficult to identify any one device as the earliest computer, partly
because the term "computer" has been subject to varying interpretations over
time.
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Originally, the
term "computer" referred to a person who performed numerical calculations (a
human computer), often with the aid of a mechanical calculating device.
Examples of early mechanical computing devices
included the abacus, the slide rule and arguably the astrolabe and the
Antikythera mechanism (which dates from about 150-100 BC). The end of the
Middle Ages saw a re-invigoration of European mathematics and engineering,
and Wilhelm Schickard's 1623 device was the first of a number of mechanical
calculators constructed by European engineers. |
However, none of those devices fit the modern
definition of a computer because they could not be programmed. In 1801, Joseph
Marie Jacquard made an improvement to the textile loom that used a series of
punched paper cards as a template to allow his loom to weave intricate patterns
automatically. The resulting Jacquard loom was an important step in the
development of computers because the use of punched cards to define woven
patterns can be viewed as an early, albeit limited, form of programmability.
In 1837, Charles Babbage was the first to conceptualize and design a fully
programmable mechanical computer that he called "The Analytical Engine".[3] Due
to limited finance, and an inability to resist tinkering with the design,
Babbage never actually built his Analytical Engine.
Large-scale automated data processing of punched cards was performed for the
U.S. Census in 1890 by tabulating machines designed by Herman Hollerith and
manufactured by the Computing Tabulating Recording Corporation, which later
became IBM. By the end of the 19th century a number of technologies that would
later prove useful in the realization of practical computers had begun to
appear: the punched card, Boolean algebra, the vacuum tube (thermionic valve)
and the teleprinter.
During the first half of the 20th century, many scientific computing needs were
met by increasingly sophisticated analog computers, which used a direct
mechanical or electrical model of the problem as a basis for computation.
However, these were not programmable and generally lacked the versatility and
accuracy of modern digital computers.