Category Archives: DOS

Floating-Point Exceptions and DOS Extenders

Posted on September 5, 2014 by Michal Necasek

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

Posted on August 8, 2014 by Michal Necasek

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 | 14 Comments

Multitasking MS-DOS 4.0, Goupil OEM

Posted on April 9, 2014 by Michal Necasek

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

Posted on March 25, 2014 by Michal Necasek

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 | 53 Comments

The Central Point Backup Floppy Format

Posted on September 24, 2013 by Michal Necasek

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 | 28 Comments

Kids these days…

Posted on September 8, 2013 by Michal Necasek

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

Posted on June 12, 2013 by Michal Necasek

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 | 20 Comments

DOS Goodies at bitsavers.org

Posted on May 27, 2013 by Michal Necasek

The excellent bitsavers.org 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

Posted on March 22, 2013 by Michal Necasek

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 | 16 Comments

Fixing Broken LINK4

Posted on March 15, 2013 by Michal Necasek

The recently-mentioned multitasking DOS 4 disk images came with a linker called LINK4.EXE. The ‘4’ in fact stands for ‘DOS 4’, although most people who used LINK4 never saw multitasking DOS 4 (LINK4 was shipped with 16-bit Windows SDKs). LINK4 was … Continue reading →

Posted in DOS, Microsoft | 5 Comments