Parallel port
A connector on the back of a PC that allows you to connect devices that use what is called a parallel interface. A parallel port is so called because it uses eight wires in parallel to send information, so a whole byte (8 bits) can be sent at the same time. Some printers, scanners, tape backup units and CD-ROM drives can be bought with parallel interfaces.
The parallel port supports four modes;

Standard : Used for output only.
Extended Bi-directional : Simple two-way data.
EPP : Enhanced Parallel Port mode.
ECP : Extended Capabilities Port mode.

Any parallel port devices that you may wish to attach, should have full instructions supplied with them that will tell you if the port capabilities need to be altered to one of the extended options above.

Serial port
An external connector on your PC that allows you connect devices such as printers, modems and a mouse. There are normally two serial ports on a PC. They are called serial because they transfer data one bit after another, in other words serially.

Universal Serial Bus (USB)
Your machine may have the potential to support the new USB (Universal Serial Bus) standard - a mechanism for eradicating the spaghetti of cables for connecting devices such as keyboards, mice, joysticks and modems in a single high-performance bus.

Keyboard and Mouse ports
Both the keyboard and mouse ports are minature DIN connectors, and although they are physically and electrically compatible, neither the keyboard nor the mouse will operate if plugged into the other's socket.