Computer

=What is a computer?= Video A programmable machine. The two principal characteristics of a computer are: 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], <span style="background-color: transparent; color: #cc3300; font-size: 12px; text-decoration: none; vertical-align: baseline;">[|printer] , or other device that lets you see what the computer has accomplished. <span style="background-color: transparent; color: #cc3300; font-size: 12px; text-decoration: none; vertical-align: baseline;">[|**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 <span style="background-color: transparent; color: #cc3300; font-size: 12px; text-decoration: none; vertical-align: baseline;">[|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: <span style="background-color: transparent; color: #cc3300; font-size: 12px; text-decoration: none; vertical-align: baseline;">[|**personal computer**] ** : ** A small, single-<span style="background-color: transparent; color: #cc3300; font-size: 12px; text-decoration: none; vertical-align: baseline;">[|user] computer based on a<span style="background-color: transparent; color: #cc3300; font-size: 12px; text-decoration: none; vertical-align: baseline;">[|microprocessor]. In addition to the microprocessor, a personal computer has a keyboard for entering data, a <span style="background-color: transparent; color: #cc3300; font-size: 12px; text-decoration: none; vertical-align: baseline;">[|monitor] for displaying information, and a <span style="background-color: transparent; color: #cc3300; font-size: 12px; text-decoration: none; vertical-align: baseline;">[|storage device] for <span style="background-color: transparent; color: #cc3300; font-size: 12px; text-decoration: none; vertical-align: baseline;">[|saving] data. <span style="background-color: transparent; color: #cc3300; font-size: 12px; text-decoration: none; vertical-align: baseline;">[|**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.
 * 1) It responds to a specific set of <span style="background-color: transparent; color: #cc3300; font-size: 12px; text-decoration: none; vertical-align: baseline;">[|instructions] in a well-defined manner.
 * 2) It can <span style="background-color: transparent; color: #cc3300; font-size: 12px; text-decoration: none; vertical-align: baseline;">[|execute] a prerecorded list of instructions (a <span style="background-color: transparent; color: #cc3300; font-size: 12px; text-decoration: none; vertical-align: baseline;">[|program] ).



<span style="background-color: transparent; color: #cc3300; font-size: 12px; text-decoration: none; vertical-align: baseline;">[|**minicomputer**] ** : ** A <span style="background-color: transparent; color: #cc3300; font-size: 12px; text-decoration: none; vertical-align: baseline;">[|multi-user] computer capable of supporting from 10 to hundreds of users simultaneously.

<span style="background-color: transparent; color: #cc3300; font-size: 12px; text-decoration: none; vertical-align: baseline;">[|**mainframe**] ** : ** A powerful multi-user computer capable of supporting many hundreds or thousands of users simultaneously. <span style="background-color: transparent; color: #cc3300; font-size: 12px; text-decoration: none; vertical-align: baseline;">[|**supercomputer**] ** : ** An extremely fast computer that can perform hundreds of millions of instructions per second.