Andrew Schulman’s “Undocumented DOS” serves as a case study in software reverse engineering, focusing on dissecting MS-DOS’s inner workings through disassembly. While external utilities like INTRSPY offer insight into Windows and QuickC functions, understanding the ‘why’ behind program behavior necessitates diving into the program itself. By closely examining key components like the INT 21h handler, readers can acquire an intuitive grasp of how DOS processes information internally. Controversially, the text delves into disassembling IO.SYS and MSDOS.SYS, uncovering the core DOS interrupt handlers. Schulman highlights the importance of venturing beyond standard descriptions of DOS functions, providing a unique perspective on a venerable operating system.
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