What type of connector is found at the end of many old keyboards?

The correct answer is a type of connector that is specifically associated with older keyboards, known as the PS/2 connector. This connector is round and typically has 6 pins, characterized by its distinct purple color for keyboards and a green color for mice. The PS/2 standard was widely used for connecting peripherals to computers prior to the ubiquity of USB connections.

While USB connectors have largely supplanted PS/2 connectors in modern peripherals due to their versatility and ease of use, PS/2 ports remain relevant in certain legacy systems or specialized environments where older hardware is still in operation. HDMI is primarily used for audio and video connections, while Thunderbolt is a newer, high-speed connector for various devices, not including keyboards. Therefore, the PS/2 connector is the most accurate choice when referring to the type of connector commonly found at the end of older keyboards.