Category Archives: DOS

Learn Something Old Every Day, Part XVI: DOS 4.0 SELECT Is Too Clever

A while ago I discovered an antique pirated copy of IBM DOS 4.00 on 5.25″ media, which was something that was missing in my archive. And by antique I mean from August 1988, when DOS 4.0 was practically brand new. … Continue reading

Posted in Archiving, DOS, IBM, PC history | Leave a comment

Where Did CP852 Come From Again?

An earlier article explored the history of codepage 852 (Latin-2 PC codepage) in released and pre-release versions of DOS and OS/2. At the time of this writing (June 2025), the earliest OS/2 build with some form of CP852 support including … Continue reading

Posted in DOS, I18N, IBM, PC history | 24 Comments

Learn Something Old Every Day, Part XV: KEYB Is Half of Keyboard BIOS

Recently I had an opportunity to reacquaint myself with the DOS KEYB utility. KEYB is interesting in that it is designed primarily for international users, but one can also run KEYB US to load KEYB with standard US layout. It … Continue reading

Posted in BIOS, DOS, IBM, Keyboard | 10 Comments

1989 Networking: 3+Open LAN Manager 1.1

The previously mentioned warez dump on archive.org contains a lot of little gems that would have been otherwise lost. One of those might be 3Com’s networking package from 1989, the 3+Open LAN Manager version 1.1. The software was released in … Continue reading

Posted in 386MAX, 3Com, DOS, LAN Manager, Microsoft, Networking, OS/2 | 15 Comments

Compaq EXTDISK.SYS

This is a follow-up to a previous post about the curious driver in Microsoft OS/2 1.21. After initially writing the article, additional information came to light, explaining why the code was there. In summer 1988, Compaq released the Deskpro 386/25, … Continue reading

Posted in Bugs, Compaq, DOS, PC history, Storage | 32 Comments

Learn Something Old Every Day, Part XIII: InDOS Is Not Enough

The other day I spent a while trying to understand the purpose of a rather strange looking piece of code inside Borland’s THELP.COM utility shipped with Turbo Pascal 6.0 (THELP.COM was misbehaving under emulated DOS). The THELP utility performs the … Continue reading

Posted in DOS, PC history, Undocumented | 14 Comments

The Other Three

A previous blog post explored the semi-mysterious yet sometimes highly useful DOS APPEND command. Now it’s time to look at its relatives: ASSIGN, JOIN, and SUBST. ASSIGN ASSIGN is the oldest of the bunch. It was written by IBM and … Continue reading

Posted in DOS, IBM, PC history | 13 Comments

DOS APPEND

For a long time, I couldn’t quite grasp what the DOS APPEND command could possibly be good for. Until I came across a situation which APPEND was made for. When I worked on organizing and building the DOS 2.11 source … Continue reading

Posted in DOS, IBM | 46 Comments

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 | 31 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