This example uses the programmer from Pololu ... Either regular or right-angled header (as pictured) can be installed in the J2 position; a hole will need to be cut in the bracket for external access.
Pre-VGA PCs use a handful of distinct video card types (CGA, Tandy, EGA, Hercules, MDA) to produce video. These have specific (but related) signaling systems, and all share a 9-pin D-Sub connector.