I/O Ports and Connectors
The I/O ports and connectors on the back panel of your computer are the gateways through which your computer system communicates with
external devices, such as a keyboard, mouse, printer, and monitor. Figure 3 identifies the I/O ports and connectors for your computer.
Figure 3. I/O Ports and Connectors
Serial and Parallel Ports Overview
The two built-in serial ports use 9-pin D-subminiature connectors on the back panel. These ports support devices such as external modems,
printers, plotters, and mice that require serial data transmission (the transmission of data one bit at a time over one line).
Most software uses the term COM (for COMmunications) plus a number to designate a serial port (for example, COM1 or COM2). The default
designations of your computer's integrated serial ports are COM1 and COM2.
The integrated parallel port uses a 25-pin D-subminiature connector on the computer's back panel. This I/O port sends data in parallel format
(where eight data bits, or one byte, are sent simultaneously over eight separate lines in a single cable). The parallel port is used primarily for
printers.
Most software uses the term LPT (for Line PrinTer) plus a number to designate a parallel port (for example, LPT1). The default designation of your
computer's built-in parallel port is LPT1.
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