I would really love to know how to do that. I need to see some code.
Ohh dear lord....
Here is some code which uses the old approach (and a new approach using GDI):
Mode 13h : http://en.wikipedia.org/wiki/Mode_13h
If you want to have fun, I recommend the tutorials linked to from the mode 13 wiki page:
For true authenticity, though, you need to grab Borland C++ 3.1 from here: https://winworldpc.com/product/borland-c/30
Id Software used that for Wolf3d..
This is amazing.