- External devices such as a keyboard, monitor, printer, mouse, and microphone, are often attached by a cable to the system unit. The interface of point of attachment to the system unit is called a port. Ports may be located at the back or front of the system unit.
- Serial ports transmit one bit of data at a time and is used on IBM PC and compatibles to connect devices such as keyboards, modem, and mouse. Parallel ports transmit a byte (8 bits) of data at a time on parallel paths and is reserved for printers and some types of external storage devices. A video port is used to connect monitor. Universal Serial Bus is port that can connect upto 127 different devices with a single connector.
