Traditional keyboards and mice plug into a round PS/2 port. The cables are identical and while some computers, especially laptops have a single port that can be used by either a mouse or keyboard, most desktops have both. The symbols are very intuitive and the ports and connectors are usually color coordinated; keyboard ports are usually purple while mouse ports are usually green.

The pins will only fit in a certain direction, but most cables have a flat side that matches the border around the port. Others will have a line marker to identify how to line the devices up. Do not force the plug; rather turn the plug until it fits snuggly.