A dedicated socket in the computer for a mouse. On the first desktop PCs, the mouse connected via the serial port, which was superseded by the PS/2 port. Today, mice plug into any USB port, although motherboards with PS/2 sockets are still made (see PS/2 port). The Apple Desktop Bus (ADB) was used for keyboards and mice on the first Macs but was later replaced with USB (see ADB). See PC input/output and USB.