Category Archives: DOS

PC DOS 1.0, But Not Quite

Posted on May 26, 2017 by Michal Necasek

Last week a most interesting image of a 160K disk arrived at the OS/2 Museum. The files on the disk image are rather old. When the disk boots up (not trivial, see below), the following message appears: Astute readers will … Continue reading →

Posted in DOS, IBM, Microsoft, PC history, Pre-release | 43 Comments

Booting Is Hard

Posted on February 23, 2017 by Michal Necasek

So I had this brilliant idea of using SCSI drives with old 286/386/486 boards which have old BIOSes that can’t handle IDE drives bigger than 500-ish megabytes. The SCSI HBA is the first one I happened to grab, an Adaptec 1542C … Continue reading →

Posted in 386, BIOS, CompactFlash, DOS, SCSI | 20 Comments

MS C 4.0 Documentation Added

Posted on November 27, 2015 by Michal Necasek

Another library expansion. This time it’s Microsoft C 4.0 documentation (1986)—because it’s not available online, is not easy to find offline, and because Jeff asked for it. MS C 4.0 was an early Microsoft compiler, implementing first glimpses of the not-yet finalized … Continue reading →

Posted in C, Documentation, DOS, Microsoft | 6 Comments

The DOS 4.0 Shell Mouse Mystery

Posted on March 21, 2015 by Michal Necasek

Several years ago, I noticed that in some virtual and physical environments, the DOS Shell in both IBM’s and Microsoft’s DOS 4.0x has a very odd glitch: the mouse pointer moves, but does not register any clicks… except on scroll … Continue reading →

Posted in DOS, IBM, PC hardware, PC history | 25 Comments

Original CEMM Unearthed

Posted on November 5, 2014 by Michal Necasek

An important fragment of PC history was unearthed a few days ago: An image of a Compaq Deskpro 386 supplemental disk from August 1986, containing among other things CEMM.EXE, Compaq’s original expanded memory emulator shipped with the Deskpro 386. The … Continue reading →

Posted in 386, Compaq, DOS | 25 Comments

386 Memory Managers and DMA

Posted on September 12, 2014 by Michal Necasek

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

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 | 6 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 | 52 Comments