I remember that my copy of Geoff Chappell's "DOS Internals" had a floppy disk with the source code taped into the last page. Still readable after 20 years. But

I remember that my copy of Geoff Chappell's "DOS Internals" had a floppy disk with the source code taped into the last page. Still readable after 20 years. But these times seem over. Today there are too many topics that are not covered by books or don't have proper documentation at all.