MS-DOS

disassembling

A blast from the past: Disassembling DOS (softwarelitigationconsulting.com) 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.]

Microsoft MS-DOS 3.20 (pcjs.com) The MS-DOS 3.20 disks in the PCjs collection are the only known non-OEM copies of that release available online. All other known MS-DOS 3.20 disk images are OEM releases (eg, HP, Zenith, Data General, Seiko Epson, etc.) and can be found on sites like WinWorld.
Microsoft MS-DOS 5.00 (pcjs.com) IBM PC AT (8Mhz), 1Mb RAM, 20Mb Hard Disk (Formatted), IBM EGA (128Kb)
Microsoft MS-DOS 6.22 (pcjs.com) IBM PC AT, 640Kb RAM, 47Mb Hard Disk, IBM EGA (128Kb)

Why are there both TMP and TEMP environment variables, and which one is right? (devblogs.microsoft.com) If you snoop around your environment variables, you may notice that there are two variables that propose to specify the location of temporary files. There is one called TMP and another called TEMP. Why two? And if they disagree, then who’s right?
Why did Windows 95 setup use three operating systems? (devblogs.microsoft.com) Twitter users @tthirtle asked why Windows 95 setup goes through three operating systems: MS-DOS, Windows 3.1, and then Windows 95. Why not go from MS-DOS straight to Windows 95?

MS-DOS (Wikipedia) MS-DOS (/ˌɛmˌɛsˈdɒs/ em-es-DOSS; acronym for Microsoft Disk Operating System, also known as Microsoft DOS) is an operating system for x86-based personal computers mostly developed by Microsoft. Collectively, MS-DOS, its rebranding as IBM PC DOS, and a few operating systems attempting to be compatible with MS-DOS, are sometimes referred to as “DOS” (which is also the generic acronym for disk operating system). MS-DOS was the main operating system for IBM PC compatibles during the 1980s, from which point it was gradually superseded by operating systems offering a graphical user interface (GUI), in various generations of the graphical Microsoft Windows operating system.