Keyboards come with one of two connectors: 5-pin DIN or 6-pin mini-DIN. The 5-pin DIN or AT connector is larger than the 6-pin mini-DIN. Most older PC keyboards used this type of keyboard connector.

The 6-pin mini-DIN, or PS/2 connector, is smaller than its 5 pin relative and is generally found on newer PCs. It looks exactly like a the connector found on a PS/2 mouse, with identical pins. However, do not mix up the PS/2 mouse and keyboard connectors.

You can easily plug your PS/2 mouse into the PS/2 keyboard connector or your PS/2 keyboard into the PS/2 mouse connector. Don't worry, this will not harm you PC. But your mouse and keyboard will not work connected up to the wrong ports.

The keyboard can store up to 20 characters in its keyboard buffer. Your PC "reads" the buffer and can retrieve those twenty characters all at once. Sometimes, if you are a very fast typist or if your PC locks up, you can fill up the buffer. If this happens when you type the 21st character, your PC will just beep at you.