The D-series of connectors was invented in 1952. The "D" connector was named after its "D" shape. The second letter was used to denote the shell size. The suffix numbering describes the number of pins and other terms such as HD M,F were used to state the density of the pins or gender. Though not entirely accurate the prefix "DB" has been used as the term for Serial, Parallel and VGA computer cables and connectors.