Category Archives: DOS

386 Memory Managers and DMA

A while ago I ran into an odd problem: A virtual machine running QEMM 9.0 (aka QEMM 97) would crash more or less every time it tried to read something from a floppy. No such problem was observable in any … Continue reading

Posted in 386, Bugs, DOS, PC hardware | 7 Comments

Floating-Point Exceptions and DOS Extenders

Recently I had a need to test the behavior of floating-point exceptions (FPEs) in environments where traditional FPE reporting is used. To briefly recap, in the original PC equipped with an 8088/8087 pair, floating-point exceptions, which are generally asynchronous events,¬†were … Continue reading

Posted in 386, Bugs, DOS, DOS Extenders, PC architecture | Leave a comment

Semantic Differences, Microsoft v. Microsoft

While comparing the behavior of various versions of old Microsoft C compilers, I tried building a trivial hello-world type program with CL.EXE from Microsoft C/C++ 7.0 (March 1992) running on top of a 32-bit Windows Server 2003. This seemingly trivial … Continue reading

Posted in DOS, Microsoft, Virtualization | 7 Comments

Multitasking MS-DOS 4.0, Goupil OEM

The recently unearthed copy of the near-mythical Multitasking (aka European) MS-DOS 4.0 clearly did not want to be alone. James Lariviere, a kind reader of this blog, provided a disk image of multitasking DOS 4 which was released in 1986 … Continue reading

Posted in DOS, Microsoft, OS/2 | 29 Comments

MS-DOS 1.1, 2.0 Source Code Released

In cooperation with the excellent Computer History Museum in Mountain View, Microsoft released the source code to MS-DOS 1.1, MS-DOS 2.0, and Microsoft Word for Windows 1.1a. Here’s hoping that this is a sign of things to come and Microsoft … Continue reading

Posted in DOS, Microsoft, PC history | 52 Comments

The Central Point Backup Floppy Format

A reader recently asked about the “native” format of Central Point Backup (CP Backup) floppies. Diskettes formatted in this manner are somewhat tricky to work with as they do not use a standard DOS format. A session with Sydex’s AnaDisk … Continue reading

Posted in DOS, Floppies | 27 Comments

Kids these days…

By sheer accident I stumbled on this document. In summary, it’s about a bunch of school kids working on a computer history preservation project and trying to archive a big box of floppies from George Alistair Sanger, a video game … Continue reading

Posted in DOS, Floppies | 22 Comments

PC DOS Retro

There’s a new DOS history and reference information website called simply “PC DOS Retro Page”. The site includes several reference pages (DOS commands, drivers, functions, internal structures) as well as a very extensive timeline of DOS releases. Vernon Brooks, the … Continue reading

Posted in DOS | 16 Comments

DOS Goodies at

The excellent last week uploaded scans of several IBM Personal Computer DOS manuals. Included are the manuals for DOS 1.0 (1982), 1.1, and 2.0, a preliminary technical reference for DOS 3.1, the DOS 3.1 user’s reference manual, and DOS … Continue reading

Posted in DOS, IBM | 1 Comment

The Oldest OS/2 Executable In the Wild

While researching the history of Microsoft’s segmented-executable linker originally called LINK4.EXE, I came across an OS/2 executable that was publicly released almost a year before the first OS/2 SDK was shipped, and many months before OS/2 was even announced. In … Continue reading

Posted in DOS, Microsoft, OS/2 | 4 Comments