types of ports on computers
Serial Port. Even though the communication in PS/2 and USB is serial, technically, the term Serial Port is used to refer the interface that is compliant to RS-232 standard. There are two types of serial ports that are commonly found on a computer: DB-25 and DE-9.
PS/2 Port. 1  Used for old computer keyboard and mouse. 2  Also called mouse port. 3  Most of the old computers provide two PS/2 port, each for mouse and keyboard.  Also known as IEEE 1284-compliant Centronics port.
VGA port is found in many computers, projectors, video cards and High Definition TVs. It is a D-sub connector consisting of 15 pins in 3 rows. The connector is called as DE-15. VGA port is the main interface between computers and older CRT monitors.