Category Archives: DOS

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 | 10 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

KEYBCS2

After writing about the likely origins of IBM code page 852, I thought I should revisit the homegrown Czech alternative solution, the Kamenick√Ĺ brothers encoding and their keyboard driver. Its existence is well documented, and the so-called (somewhat misnamed) KEYBCS2 … Continue reading

Posted in DOS, I18N, IBM, x86 | 29 Comments

Where Did CP852 Come From?

In the 1990s, a lot of my documents were written in code page 852 (CP852), also known as PC Latin 2. This code page is sometimes called “Eastern European”, which is a bit misleading, given that it does not cover … Continue reading

Posted in DOS, I18N, IBM, Microsoft, OS/2, PC history | 47 Comments

Another Myth Busted

More than once I came across a story of a heroic MicroPro programmer who in an all-night session managed to port WordStar from CP/M to DOS by patching a single byte. This is how the legend was retold by Joel … Continue reading

Posted in CP/M, DOS, PC history, WordStar | 5 Comments

Unidentified PC DOS 1.1 Boot Sector Junk Identified

Anyone trying to disassemble the PC DOS 1.1 boot sector soon notices that at offsets 1A3h through 1BEh there is a byte sequence that just does not belong. It appears to be a fragment of code, but it has no … Continue reading

Posted in Development, DOS, PC history | 24 Comments