Undocumented Windows

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1. markus_zhangJun 2026
   I think they learned by reading books such as Undocumented Windows or Windows Internals (not to be confused with Windows NT internals), and Microsoft documents.

   In fact, I’d argue it was more fun than programming Javascript these days.

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2. jngOct 2019
   Windows is not written in C++, even if Microsoft did embrace C++ quite a bit with the infamous MFC and so on. Windows was originally written using C and assembly language, using the Pascal calling convention for efficiency. It was originally a layer on top DOS which was written in assembly language. Being a "layer" or not was the subject of a very complex federal antitrust case back in the 90s. You can read "Undocumented DOS" and "Undocumented Windows" for some weird kind of technical investigation thriller which I found weirdly fascinating back in the day.
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3. username42Nov 2013
   I am not forgetting. Your comparison of Microsoft and Apple is unfair, I have another way to present it: "Apple stole ideas from laboratories and created a market for them. Microsoft copied successful market products to make them better integrated in windows and to sell them better."

   The article http://www.pff.org/issues-pubs/pops/pop7.4microsoftmonopolyf... gives irrefutable facts. Do not accuse me of rewriting the history. I was there to see the birth and death of many good products that have been killed by Microsoft tactics (dr dos, stacker, framemaker, borland C++, ...). One of my most usefull book at that time was http://www.amazon.com/Undocumented-Windows-Programmers-Micro.... Many people have lost a lot of time because of the monopoly of Microsoft. How much time lost because of IE6 ? I have lost a lot of time between 1999 and 2002 because visual C++ was not compliant at all with the standard published in 98.

   My opinion is that all the time lost because of Microsoft has been detrimental to computer science progress.

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4. zabzonkApr 2026
   Well, that takes me back! There are other well-produced books in the same series - anyone remember "Undocumented Windows"?
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5. adrian_bMar 2025
   The answers at your link explain pretty well what kind of APIs these were and they provide sources, e.g. the several books that have been published under titles like "Undocumented Windows ...". There were no magic APIs, just ordinary functions that covered various features not yet implemented in the publicly available Win32 API.

   Keep in mind also that the Windows kernel system calls were never accessible directly, like in Linux or the like, but as an external developer you were at the mercy of the user libraries provided by Microsoft. If the documented user libraries did not cover all the features actually implemented by the operating system, there was no way to use them without reverse engineering.

   This is now pretty much ancient history and later such APIs have been documented by Microsoft, e.g. in the "Windows Protocols Specifications", mostly as a consequence of lawsuits and investigations by the European Union and FTC.

   However when that happened, around 2000, the damage had already been done and the competition had been eliminated.

   The dominance of Microsoft in office suites that has been achieved during the transition from MS-DOS to Windows 95, than Windows 98, has succeeded in good part because of the great increase in the number of computer users during this time.

   For newbies, the MS Office suite took very well advantage of the new features enabled by a GUI and MS Office was very easy to use, while the Windows versions of the older MS-DOS programs, like Lotus 1-2-3 and WordPerfect were much less polished than MS Office, while simultaneously losing their previous keyboard-based user interface, which for experienced users had been much faster at accomplishing any task than any Microsoft GUI.

   So the MS Office GUI alternatives were neither easier to use nor faster, therefore not even their former users had any reason to stick with them, while all the newbies were naturally attracted to MS Office.

   Moreover, starting with Windows 95, Microsoft has convinced somehow all the hardware peripheral add-on-cards to stop documenting their products, but instead of that deliver them together with only Windows device drivers.

   Since that time, the non-Microsoft operating systems had to rely mostly on reverse-engineering for being able to run on modern hardware. Many years later, the situation has improved somewhat, but only for certain classes of peripherals, like network interface cards, where the vendors typically also provide Linux drivers now.

   This has hit also the old MS-DOS programs like Lotus 1-2-3, which had tons of drivers for various kinds of now obsolete Super-VGA video cards, so on new computers with Windows 95 or later they had to run in some less performant video mode that was supported directly or through emulation on modern graphic cards, unlike the Windows programs that could take full advantage of the hardware. This has contributed to the obsolescence of the better MS-DOS programs, because even if Windows 95 could run them in Virtual 8086 mode they did not work as well as on the older computers for which the MS-DOS programs had drivers that took advantage of enhanced features.

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6. fourtharkJul 2024
   I saw Schulman present how he discovered the dirty tricks Microsoft used to hobble Windows betas on DR-DOS, using similar techniques. This was at Ralph Nader's Appraising Microsoft conference in 1997.

   It's covered in another of his books, Undocumented Windows.

   Impressive work, and very brave at the time.

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