Dell 4100 - Appendix B I;O Ports and Connectors; I;O Ports and Connectors; Serial and Parallel Ports; Figure B-1. I;O Ports and Connectors

I/O Ports and Connectors B-1
Appendix B
I/O Ports and Connectors
This appendix provides specific information about the
input/output (I/O) ports and connectors on the back panel
of the computer
I/O Ports and Connectors
The I/O ports and connectors on the back panel of the
computer are the gateways through which the computer
system communicates with external devices, such as a
keyboard, mouse, printer, and monitor. Figure B-2 identi-
fies the I/O ports and connectors for your system.
Serial and Parallel Ports
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 transmis-
sion 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 com-
puter’s built-in serial ports are COM1 and COM2. COM1
is the bottom connector; COM2 is on the top.
The built-in 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 the computer’s built-in paral-
lel port is LPT1.
Port designations are used, for example, in software
installation procedures that include a step in which you
identify the port to which a printer is attached, thus tell-
ing the software where to send its output. (An incorrect
designation prevents the printer from printing or causes
scrambled print.)