A computer is a programmable machine that
receives input, stores and manipulates data, and provides output in a
useful format.
Although mechanical examples of computers have existed
through much of recorded human history, the first electronic computers
were developed in the mid-20th
century (1940–1945).
These were the size of a large room, consuming
as much power as several hundred modern personal computers (PCs).
Modern
computers based on integrated circuits are millions to billions of times
more capable than the early machines, and occupy a fraction of the space.
Simple computers are small enough to fit into small pocket devices, and can
be powered by a small battery.
Personal computers in their various forms
are icons of the Information Age and are what most people think of as "computers".
However, the embedded computers found in many devices from MP3 players to
fighter aircraft and from toys to industrial robots are the
most numerous.
The ability to store and execute lists of instructions called
programs makes computers extremely versatile, distinguishing 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 ranging from a notebook to a supercomputer are all able to perform
the same computational tasks, given enough time and storage capacity.
Source: Wikipedia
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