Computers

Computers are programmable electronic devices that accept data, execute prerecorded instructions, perform mathematical and logical operations, and output results. Software provides information to a central processing unit (CPU) that executes instructions and controls the operation of other hardware components. Memory allows computers to store data and programs temporarily. Mass storage devices such as tape and disk drives provide long-term storage for large amounts of data. Input devices such as a keyboard and mouse allow users to enter information that can be output on a display screen, printer, self-serve kiosk, or personal digital assistant (PDA). Computers, which require a bus to transmit data from one location to another, are generally classified by size and power. They feature a variety of CPU types and are available with many different operating systems. Spreadsheet, database, work processing, and graphic design applications provide specific functionality.

There are several types of computers. Supercomputers are fast, expensive machines that are used in applications that perform a very large number of mathematical calculations. The main difference between supercomputers and mainframes is that supercomputers execute a few programs as quickly as possible whereas mainframes execute many programs concurrently. Minicomputers are mid-range devices that are smaller and less powerful than mainframes but larger and more powerful than workstations, client computers that connect to a network and share data with other machines. Thin clients are low-cost, centrally managed computers that do not include CD-ROM players, diskette drives, and expansion slots. Laptop and notebook personal computers (PCs) are portable. Tablet PCs use digital ink technology and are equipped with a special-purpose pen called a stylus. Pocket PCs are advanced PDAs with low-power processors, transflective color screens, wireless communication features, and one or more expansion slots.

Selecting computers requires an analysis of storage specifications. Some devices include integrated drive electronics (IDE), a small computer system interface (SCSI), or a random array of independent discs (RAID). Other devices include a tape drive, a 1.44 MB 3.5” floppy drive, or removable magneto-optic (MO) storage technology. Computers with drives that can read or record compact disks (CDs) are commonly available. Compact disk read-only memory (CD-ROM) drives can read but not record information. By contrast, compact disk recordable (CD-R) drives can write once and read many times while compact disk rewritable (CD-RW) drives can read, write, erase, and rewrite disks. Disc drives that can read or record digital versatile discs (DVDs) are also available.

Computers can mount on panels or racks and often include a monitor for displaying information. Cathode-ray tube (CRT) devices use an electron beam to illuminate phosphor dots and are suitable for applications that require relatively high screen resolutions. Flat panel displays, which are often very thin, are used with portable or laptop computers and include technologies such as liquid crystal display (LCD) and gas plasma.

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Part Numbers for Computers