Digital lines and ports are important parts of a digital input/output system.
Line—A line is an individual signal. It refers to a physical terminal. The data that the line carries are called bits, binary values that are either 1 or 0. The terms line and bit are fairly interchangeable. For example, an 8-bit port is the same as a port with eight lines.
Port—A port is a collection of digital lines. Usually, the lines are grouped into an 8-bit or 32-bit port.
Port Width—The port width refers to the number of lines in a port. For example, a device with one port with eight lines has a port width of eight.