Computer

A computer is a machine that manipulates data according to a list of instructions.

The first devices that resemble modern computers date to the mid-20th century (1940–1945), although the computer concept and various machines similar to computers existed earlier.

Early electronic computers were the size of a large room, consuming as much power as several hundred modern personal computers (PC).[1] Modern computers are based on tiny integrated circuits and are millions to billions of times more capable while occupying a fraction of the space.[2] Today, simple computers may be made small enough to fit into a wristwatch and be powered from a watch battery. Personal computers, in various forms, are icons of the Information Age and are what most people think of as "a computer"; however, the most common form of computer in use today is the embedded computer. Embedded computers are small, simple devices that are used to control other devices — for example, they may be found in machines ranging from fighter aircraft to industrial robots, digital cameras, and children's toys.

The ability to store and execute lists of instructions called programs makes computers extremely versatile and distinguishes 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 with capability and complexity ranging from that of a personal digital assistant to a supercomputer are all able to perform the same computational tasks given enough time and storage capacity.

From Wikipedia, the free encyclopedia

Computer

A programmable machine. The two principal characteristics of a computer are:

• It responds to a specific set of instructions in a well-defined manner.
• It can execute a prerecorded list of instructions (a program).
  

Modern computers are electronic and digital. The actual machinery -- wires, transistors, and circuits -- is called hardware; the instructions and data are called software.

All general-purpose computers require the following hardware components:

• memory : Enables a computer to store, at least temporarily, data and programs.
  
• mass storage device : Allows a computer to permanently retain large amounts of data. Common mass storage devices include disk drives and tape drives.
  
• input device : Usually a keyboard and mouse, the input device is the conduit through which data and instructions enter a computer.
  
• output device : A display screen, printer, or other device that lets you see what the computer has accomplished.
  
• central processing unit (CPU): The heart of the computer, this is the component that actually executes instructions.
  

In addition to these components, many others make it possible for the basic components to work together efficiently. For example, every computer requires a bus that transmits data from one part of the computer to another.

Computers can be generally classified by size and power as follows, though there is considerable overlap:

• personal computer : A small, single-user computer based on a microprocessor. In addition to the microprocessor, a personal computer has a keyboard for entering data, a monitor for displaying information, and a storage device for saving data.
  
• workstation : A powerful, single-user computer. A workstation is like a personal computer, but it has a more powerful microprocessor and a higher-quality monitor.
  
• minicomputer : A multi-user computer capable of supporting from 10 to hundreds of users simultaneously.
  
• mainframe : A powerful multi-user computer capable of supporting many hundreds or thousands of users simultaneously.
  
• supercomputer : An extremely fast computer that can perform hundreds of millions of instructions per second