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).
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.
A computer is a programmable machine that receives input, stores and manipulates data//information, and provides output in a useful format. 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 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.
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.
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.
Mini Computer : 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.
Super Computer : An extremely fast computer that can perform hundreds of millions of instructions per second.