The PS/2 standard, introduced by IBM in 1987, stands for Personal System/2. A PS/2 port is an electronic receptacle or plug found on computers. It accepts a PS/2 cable with a mini-DIN connector, and is most often used to plug in a keyboard or mouse.
The port is "female," which means that it has holes into which the cable pins are inserted, while the mini-DIN cable is "male." The connector is small with a diameter of about 1/3 inch (9.5 mm). It features a metal sleeve that is notched to ensure proper alignment when inserting it into the port. This protects the circular pins inside the DIN connector from becoming bent.
The PS/2 port was initially a large DIN plug used for a keyboard, while the mouse was commonly plugged into a serial port. As modems also used serial ports, however, configuration conflicts between mouse and modem became a common problem as each tried to share the same IRQ or memory address. To fix the problem, one could purchase a "bus mouse," or a card that could be installed in the computer and featured a rear PS/2 port for the mouse. The PS/2 mouse was a popular solution because it worked independent of the serial port and avoided configuration problems. Eventually, computers incorporated two built-in ports, one for the keyboard and one for a mouse.
People who want to buy an extension cable for a PS/2 keyboard or mouse should be sure to check the pin configuration to ensure they are purchasing the correct cable. There are seven different configurations for mini-DIN plugs that all look like standard PS/2 plugs at a glance. The cable should specify what equipment is it made for. S-Video cable looks similar to mini-DIN cables, for example, but the keyed notch in the metal sleeve and pin arrangement differ.
Although PS/2 ports remain in widespread use, subsequent technologies have lessened the need for them. Many manufacturers of keyboards and mice have introduced models that use USB (Universal Serial Bus) ports instead, and other models are wireless. This gives the consumer the choice to bypass the PS/2 port completely.