Keyboard cables can use any of several different connector types. Before purchasing a new keyboard, verify what connector type you need to ensure that the new keyboard will be compatible with your computer. Check the back of your computer for the type of port and purchase a keyboard that fits your system.
The 5-pin DIN connector was the first widespread non-proprietary keyboard cable connector. It was a bit larger than today's connectors, and had five pins which were oriented asymmetrically to ensure a proper connection. This connector is often referred to as an AT connector, referring to the IBM system that popularized the format. These connectors are not widely used today,
The 6-pin mini-DIN connector is a replacement for the original 5-Pin design. This connector is smaller, and is typically colored purple to differentiate it from the similar mouse connector. This type of connector is often referred to as a PS/2 connector and is also named for the IBM system that popularized it. This format is widely used in desktop computers.
USB is an extremely common keyboard cable connector type. This small rectangular connector provides a major upgrade over the DIN connector types. USB connectors are hot-swappable, meaning that you can unplugged them and plug them in without turning off the system. AT and PS/2 devices are not hot-swappable.