|
 A computer is a machine for
manipulating data according to a list of instructions, or program.
The ability to store and execute stored programs—that is,
programmability—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 so
long as time and storage capacity are not considerations.
A computer in a wristwatch.Computers take numerous physical forms. Early
electronic computers were the size of a large room, consuming as much
power as several hundred modern personal computers. [1] Today, computers
can be made small enough to fit into a wrist watch and powered from a
watch battery. However, large-scale computing facilities still exist for
specialized scientific computation and for the transaction processing
requirements of large organizations. Society has come to recognize
personal computers and their portable equivalent, the laptop computer,
as icons of the information age; they 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
are used to control machines from fighter aircraft to industrial robots,
digital cameras, and even children's toys.
History of computing :
The Jacquard loom was one of the first programmable devices.The question
of which was the earliest computer is a difficult one. The very
definition of what a computer is has changed over the years and it is
therefore impossible to definitively answer the question. Many devices
once called "computers" would no longer qualify as such by today's
standards.
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 87 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. While the resulting Jacquard loom is not considered to be
a computer, it was an important step 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".[2] Due to limits of finances, 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 US Census in 1890 by tabulating machines designed by Herman
Hollerith and manufactured by the Computing Tabulating Recording
Corporation (CTR), which later became IBM. So 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.
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 didn't 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.
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.
Sources : Internet
Search Engines Result |
