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).[1] 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.[2] 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 netbook to a supercomputer are all able to perform the
same computational tasks, given enough time and storage capacity
.