A computer is a programmable machinedesigned to sequentially and automatically carry out a sequence of arithmetic or logical operations. The particular sequence of operations can be changed readily, allowing the computer to solve more than one kind of problem.
Conventionally a computer consists of some form of memory
for data storage, at least one element that carries out arithmetic and
logic operations, and a sequencing and control element that can change
the order of operations based on the information that is stored.
Peripheral devices allow information to be entered from an external
source, and allow the results of operations to be sent out.
A computer's processing unit executes series of instructions that make it read, manipulate and then store data.
Conditional instructions change the sequence of instructions as a
function of the current state of the machine or its environment.
The first electronic computers were developed in the mid-20th century
(1940–1945). Originally, they 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 mobile devices, and Mobile_computing]mobile computers can be powered by small batteries. Personal computers in their various forms are 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.