Author Archives: Michal Necasek

Learn Something Old Every Day, Part XI: DOS Directory Searches are Bizarre

Posted on May 7, 2024 by Michal Necasek

A while ago I started playing with EMU2, a piece of software which calls itself “A simple text-mode x86 + DOS emulator”. It is indeed relatively simple, only emulating an 8086 (or maybe 80186, with little bits of 80286 here … Continue reading →

Posted in Development, DOS, Undocumented | 53 Comments

Learn Something Old Every Day, Part X: The VGA Attribute Controller Is Weird

Posted on May 3, 2024 by Michal Necasek

A few days ago I finally swatted a VGA emulation bug that I had known about for several years, but couldn’t identify until recently. The problem affected only Windows 3.1 running in Standard mode. It did not occur in Windows … Continue reading →

Posted in Bugs, PC hardware, VGA | 9 Comments

How Not To Release Historic Source Code

Posted on April 26, 2024 by Michal Necasek

This is how to not do it: GitHub Don’t get me wrong, it’s absolutely brilliant that Microsoft was able to release a fairly complete (minus DOSSHELL) source code for MS-DOS 4.00 or 4.01 (see below). As much as it was … Continue reading →

Posted in Development, DOS, Source code | 83 Comments

The Future That Never Was

Posted on March 4, 2024 by Michal Necasek

Microsoft OS/2 2.0 SDK Pre-Release 2, June 1990 In 1990, the strategic PC operating system of Microsoft and IBM was not DOS, not Windows, but OS/2. The first 16-bit OS/2 was initially released in 1987 with a reduced feature set, … Continue reading →

Posted in 386, IBM, LAN Manager, Microsoft, OS/2, PC history, Pre-release | 76 Comments

Unlocking NetWare 2.0a

Posted on February 23, 2024 by Michal Necasek

A few months ago, the OS/2 Museum obtained a seemingly complete and error-free set of floppies with SFT NetWare 286 Level II version 2.0a. And just recently, a disk set of Advanced NetWare 86 2.0a turned up, though sadly incomplete. … Continue reading →

Posted in NetWare, Software Hacks | 23 Comments

Tarbell to Cromemco

Posted on January 23, 2024 by Michal Necasek

While playing around with old versions of 86-DOS, I came across a disk image of 86-DOS 1.14. I ran the older 86-DOS versions in the SIMH simulator which can emulate the Cromemco disk controller supported by 86-DOS. Unfortunately the 86-DOS … Continue reading →

Posted in Development, DOS, PC history | 16 Comments

Misconceptions on Top of Misconceptions

Posted on January 18, 2024 by Michal Necasek

While researching the precise meaning of the Ctrl-Z (26 decimal, hex 1Ah, ASCII SUB) character in DOS, I was somewhat taken aback by this article which purports to correct a common misconception. The article is, for the most part, entirely … Continue reading →

Posted in DOS | 21 Comments

86-DOS Revisited

Posted on January 15, 2024 by Michal Necasek

At the end of December 2023, several disk images of very old versions of Seattle Computer Products 86-DOS unexpectedly turned up. This includes previously unseen releases of 86-DOS version 0.11 and 0.34 (going by the version number in the 86-DOS … Continue reading →

Posted in DOS, PC history | 24 Comments

From the Annals of Preprocessor Hackery

Posted on October 22, 2023 by Michal Necasek

Over the last few days I’ve been slowly attacking the source code for 386MAX, trying to build the entire product. One of the many problems I ran into turned out to be quite interesting. There are several (16-bit) Windows components … Continue reading →

Posted in 386MAX, C, Development, Microsoft | 25 Comments

VDS: Borne out of Necessity

Posted on October 5, 2023 by Michal Necasek

In July 1990, Microsoft released a specification for Virtual DMA Services, or VDS. This happened soon after the release of Windows 3.0, one of the first (though not the first) providers of VDS. The VDS specification was designed for writers … Continue reading →

Posted in 386, Documentation, Microsoft, PC history, Windows | 10 Comments