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: 869