Every one must purchase assembled PC because we can get quality product according to our need and its servicing as also very easy. A computer is a general purpose device which can be programmed to carry out a finite set of arithmetic or logical operations. Since a sequence of operations can be readily changed, the computer can solve more than one kind of problem. The essential point of a computer is to implement an idea, the terms of which are satisfied by Alan Turing’s Universal Turing machine.
Conventionally, a computer consists of at least one processing element and some form of memory. The processing element carries out arithmetic and logic operations, and a sequencing and control unit that can change the order of operations based on stored information. Peripheral devices allow information to be retrieved from an external source, and the result of operations saved.
A computer’s processing unit executes a 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.
In order to interact with such a machine, programmers and engineers developed the concept of a user interface in order to accept input from humans and return results for human consumption.
The first electronic digital computers were developed between 1940 and 1945 in the United Kingdom and United States.
Originally, they were the size of a large room, consuming as much power as several hundred modern personal computers(PCs). [ 1 ] In this era mechanical analog computers were used for military applications.