In any case, there is a lot more documentation on the Web. As usual, start with the Web site for your particular distribution. Ports and Modems A computer has a number of connections between the inside of the box and the outside world. Most PCs come with two serial ports and one parallel port. Serial ports transmit data over one wire in a serial fashion, one bit at a time, and then reassemble it into bytes.
Parallel ports use eight wires to send eight bits in parallel at one time.
Most printers for home use connect to the PC's parallel port. A modem is a device that lets you send digital information over a telephone line. This is common these days, but remember that the telephone system as we know it was originally designed to carry voice only. The modem was a breakthrough technology that modulates the digital data, converting it into an analog signal that can be sent over a telephone line. Modem is short for modulator-demodulator.