A serial interface is a computer interface that delivers data down a single wire or single pair of wires. Amongst the many uses of serial communications in desktop computers, it was used for early PC mice, before the advent of the PS/2 interface. Serial interfaces are a concept, for which there are numerous implementations, and numerous connectors. In particular, while PCs use a male DE-9 socket, Macintosh computers used female mini-DIN-8 sockets. Macintosh computers were fitted with dual serial ports, while PCs typically used only one, with a parallel port being used in place of the other.
The DE-9 serial interface on desktop PCs was superseded by USB; laptops in particular typically omit the serial port now, while desktop PCs may still have one present.