Ports are of five types.* A parallel port allows lines to be connected that will enable 8 bits to be transmitted simultaneously, like cars on an eight-lane highway. Parallel lines move information faster than serial lines do, but they can transmit information efficiently only up to 15 feet. Thus, parallel ports are used principally for connecting printers.
* A serial port, or RS-232 port, enables a line to be connected that will send bits one after the other on a single line, like cars on a one-lane highway. Serial ports are used principally for communications lines, modems, and mice. (They are frequently labeled "COM" for communications.)
* Video adapter ports are used to connect the video display monitor outside the computer to the video adapter card inside the system unit. Monitors may have either a 9-pin plug or a 15-pin plug. The plug must be compatible with the number of holes in the video adapter card.
* SCSI port Pronounced "scuzzy" (and short for Small Computer System Interface), a SCSI port provides an interface for transferring data at high speeds for up to eight SCSI-compatible devices. These devices include external hard-disk drives, CD-ROM drives, and magnetic-tape backup units.
* Game ports allow you to attach a joystick or similar game-playing device to the system unit.
Why are so many ports needed? Why can't plugging peripherals into a computer be as easy as plugging in a lamp in your living room? The reason, says an Intel engineer, is that "The PC industry has evolved ad hoc. We were : always adding one more piece of equipment." As a result, connecting a new device, such as a scanner or a second printer, "is about as straightforward as triple-bypass surgery," says one writer. In. many cases, it involves opening the computer and inserting a circuit board, installing or modifying pertinent software, and fiddling with little switches.
Date: 2015-04-20; view: 954
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