A computer is a machine that manipulates data according to a

set of instructions.

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 a wristwatch, and can be powered by a watch battery.

Personal computers in their various forms are icons of the

Information Age and are what most people think of as

"computers". The embedded computers found in many devices
 
from MP3 players to fighter aircraft and from toys to industrial

robots are however 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 mobile phone to a super

computer are all able to perform the same computational tasks,

given enough time and storage capacity.