From 0 to 1 MB in DOS

Since the last article on the text-based IDEs of old, I've been meaning to write about the GCC port to DOS, namely DJGPP. As I worked on the draft for that topic, I realized that there is a ton of ground to cover to set the stage so I took most of the content on memory management out and wrote this separate post.

This article is a deep dive on how DOS had to pull out tricks maximize the use of the very limited 1 MB address space of the 8086. Those tricks could exist because of the features later introduced by the 80286 and the 80386, but these were just clutches to paper over the fact that DOS could not leverage the real improvements provided by protected mode.

Julio Merino

The DOS memory story is a string of hacks upon hacks that somehow managed to work - and that still work today.