- from Undocumented DOS: A Programmer’s Guide to Reserved MS-DOS Functions and Data Structures (2nd edition, 1994. Copyright (c) Andrew Schulman 1994-2020. All rights reserved. [This nearly-ancient text (along with others from Undocumented DOS and Undocumented Windows) is being presented as a case study in some methodologies of software reverse engineering, applied to mass-market software. Note that this chapter appeared in the 2nd edition of the book, not in the 1st edition.]