The D-sub series of connectors was introduced by ITT Cannon in 1952.Cannon's part-numbering system uses D as the prefix for the whole series, followed by one of A, B, C, D, or E denoting the shell size, followed by the number of pins or sockets, followed by either P (male) or S (female) denoting the gender of the parts. Each shell size usually corresponds to a certain number of pins or sockets: The contacts in each row of these connectors are spaced 326/3000 of an inch apart, or approximately 0.1087 inches (2.76 mm), and the rows are spaced 0.112 inches (2.84 mm) apart. The pins in the two rows are offset by half the distance between adjacent contacts in a row. This spacing is called standard density. The suffixes M and F (for male and female) are sometimes used instead of the original P and S for plug and socket.
Later D-sub connectors added extra pins to the original shell sizes, and their names follow the same pattern. For example, the DE-15, usually found in VGA cables, has 15 pins in three rows, all surrounded by an E size shell. The pins are spaced at 0.090 inches (2.3 mm) horizontally and 0.078 inches (2.0 mm) vertically, in what is called high density. The other connectors with the same pin spacing are the DA-26, DB-44, DC-62, DD-78 and DF-104. They all have three rows of pins, except the DD-78 which has four, and the DF-104 which has five rows in a new, larger shell. The double density series of D-sub connectors have even denser configurations and consists of the DE-19, DA-31, DB-52, DC-79, and DD-100. These each have three rows of pins, except the DD-100, which has four.