|
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.
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". 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.
A succession of steadily more
powerful and flexible computing devices were constructed in the
1930s and 1940s, gradually adding the key features that are seen
in modern computers. The use of digital electronics (largely
invented by Claude Shannon in 1937) and more flexible
programmability were vitally important steps, but defining one
point along this road as "the first digital electronic computer"
is difficult (Shannon 1940). Notable achievements include:
EDSAC was one of the first computers to implement the stored
program (von Neumann) architecture.
* Konrad Zuse's electromechanical "Z machines". The Z3 (1941)
was the first working machine featuring binary arithmetic,
including floating point arithmetic and a measure of
programmability. In 1998 the Z3 was proved to be Turing
complete, therefore being the world's first operational
computer.
* The non-programmable Atanasoff – Berry Computer (1941) which
used vacuum tube based computation, binary numbers, and
regenerative capacitor memory.
* The secret British Colossus computer (1944), which had limited
programmability but demonstrated that a device using thousands
of tubes could be reasonably reliable and electronically
reprogrammable. It was used for breaking German wartime codes.
* The Harvard Mark I (1944), a large-scale electromechanical
computer with limited programmability.
* The U.S. Army's Ballistics Research Laboratory ENIAC (1946),
which used decimal arithmetic and is sometimes called the first
general purpose electronic computer (since Konrad Zuse's Z3 of
1941 used electromagnets instead of electronics). Initially,
however, ENIAC had an inflexible architecture which essentially
required rewiring to change its programming.
Several developers of ENIAC, recognizing its flaws, came up with
a far more flexible and elegant design, which came to be known
as the stored program architecture or von Neumann architecture.
This design was first formally described by John von Neumann in
the paper "First Draft of a Report on the EDVAC", published in
1945. A number of projects to develop computers based on the
stored program architecture commenced around this time, the
first of these being completed in Great Britain. The first to be
demonstrated working was the Manchester Small-Scale Experimental
Machine (SSEM) or "Baby". However, the EDSAC, completed a year
after SSEM, was perhaps the first practical implementation of
the stored program design. Shortly thereafter, the machine
originally described by von Neumann's paper — EDVAC — was
completed but did not see full-time use for an additional two
years.
Nearly all modern computers implement some form of the stored
program architecture, making it the single trait by which the
word "computer" is now defined. By this standard, many earlier
devices would no longer be called computers by today's
definition, but are usually referred to as such in their
historical context. While the technologies used in computers
have changed dramatically since the first electronic,
general-purpose computers of the 1940s, most still use the von
Neumann architecture. The design made the universal computer a
practical reality.
Microprocessors are miniaturized devices that often implement
stored program CPUs.
Vacuum tube-based computers were in use throughout the 1950s,
but were largely replaced in the 1960s by transistor-based
devices, which were smaller, faster, cheaper, used less power
and were more reliable. These factors allowed computers to be
produced on an unprecedented commercial scale. By the 1970s, the
adoption of integrated circuit technology and the subsequent
creation of microprocessors such as the Intel 4004 caused
another leap in size, speed, cost and reliability. By the 1980s,
computers had become sufficiently small and cheap to replace
simple mechanical controls in domestic appliances such as
washing machines. Around the same time, computers became widely
accessible for personal use by individuals in the form of home
computers and the now ubiquitous personal computer. In
conjunction with the widespread growth of the Internet since the
1990s, personal computers are becoming as common as the
television and the telephone and almost all modern electronic
devices contain a computer of some kind.
|