I think he meant to use it to replace gdi. Just write into a texture which you render as fullscreen quad/blit into the backbuffer, or write directly into the backbuffer, but I am not sure if that is possible anymore.

Lite-C Tut. 1 Lite-C Tut. 2 Lite-C Tut. 3 (en)
Shader Tutorial (ger)

http://www.slindev.com