The IO ports are constituted in the means by which the microprocessor of a computer communicates with its surroundings. Ports for each interaction of the unit of main processing with their auxiliary devices exist. Thus, it exists a port of input for the keyboard, an outport for the video, a port of input  for the mouse, etc. The Personal computer (PC) can address until 64K IO ports. Each port is designated by a number. Next the address in hexadecimal are listed of the most usual IO ports