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Category Archives: DOS
Who Knew What When
When Microsoft released the unique early beta build of Multitasking DOS 4, I quickly found out that it does not run in VirtualBox: This was a bit of a surprise, because the more-or-less released versions of Multitasking DOS 4 from … Continue reading
Posted in 286, DOS, IBM, Microsoft, PC architecture, PC history, VirtualBox
30 Comments
Learn Something Old Every Day, Part XII: Strange File Resizing on DOS
Someone recently asked an interesting question: Why do Microsoft C and compatible DOS compilers have no truncate() and/or ftruncate() library functions? And how does one resize files on DOS? OK, that’s actually two questions. The first one is easy enough … Continue reading
Posted in Computing History, CP/M, Development, Documentation, DOS, Microsoft
29 Comments
Learn Something Old Every Day, Part XI: DOS Directory Searches are Bizarre
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
How Not To Release Historic Source Code
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
82 Comments
Tarbell to Cromemco
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
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
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
386MAX and EISA DMA
A few weeks back I was reminded that the source code to the 386MAX (later Qualitas MAX) memory manager was released in 2022 on github. Back in the 1990s I used primarily EMM386 and QEMM, but I have some experience … Continue reading
Posted in 386MAX, DOS, EISA, Source code
11 Comments
Tracking Down a Bug
When I first encountered the Unix vi editor many years ago, I recoiled in horror. It was nothing like the editors I was used to—Borland IDEs, DOS 5.0/6.x EDIT, or OS/2 and Windows editors. But over the years, I learned … Continue reading
Posted in Debugging, Development, DOS, Watcom
14 Comments
PC Disk Sector Sizes and Booting
Everyone knows that the IBM PC established 512-byte sectors on floppies and hard disks as the standard, which survived for several decades until the advent of “native” 4K-sector drives. Of course what “everyone knows” is not necessarily the whole story. … Continue reading
Posted in BIOS, DOS, IBM, PC history, Storage
15 Comments