86-DOS Was an Original

Posted on August 10, 2012 by Michal Necasek

In case it wasn’t sufficiently obvious already: A forensic expert now confirmed that 86-DOS, née QDOS, and (by extension) MS-DOS were not copies of CP/M, either on source or binary level. This comes hardly as a surprise, despite years (nay, decades) of vague accusations against Tim Paterson and Microsoft.

Proving that 86-DOS was a copy of CP/M was always going to be very much an uphill battle based on what was known of the operating systems. 86-DOS ran on 16-bit 8086 systems, while CP/M at the time was 8-bit only (8080, Z-80); in fact the unavailability of CP/M on the 8086 was the sole reason why 86-DOS was written in the first place.

While 86-DOS was compatible with the CP/M API, it used a completely different disk management strategy (based on the FAT idea of Microsoft’s Marc McDonald) and DOS-formatted disks were never compatible with CP/M. In addition, 86-DOS supported the 8086 segmented architecture and accepted 16:16 far pointers for input/output buffers passed to DOS (because the segment address was passed in DS, small model programs, including those converted from CP/M, could ignore this feature). There was no equivalent in 8-bit CP/M. Continue reading →

Posted in DOS, Microsoft, PC history | 6 Comments

Another witness against WordStar

Posted on August 2, 2012 by Michal Necasek

Previous posts examined the question why IBM implemented the A20 hardware in the PC/AT, causing endless headaches to future PC hardware and software developers. WordStar emerged as a possible culprit, but no one would quite point the finger at it.

The OS/2 Museum is now in possession of the original MS-DOS Encyclopedia (1986) which identifies WordStar in print. This is the same book that Larry Osterman claimed to have been subject to a publisher recall; either Microsoft Press didn’t do a very good job of pulling the book from the shelves or Larry Osterman’s recollection is inaccurate, but the book isn’t very difficult to find. (However, at about 8 pounds, or nearly 4 kilograms, it is quite difficult to carry around!) Continue reading →

Posted in DOS, PC history, WordStar | 17 Comments

Book Review: Inside OS/2

Posted on July 23, 2012 by Michal Necasek

A Few Decades Late Book Reviews

Inside OS/2, by Gordon Letwin
Microsoft Press, February 1988; 302 pages, ISBN 1-55615-117-9; $19.95

Letwin’s Inside OS/2 was one of the first books devoted to OS/2. What sets Inside OS/2 apart from other OS/2 books published at the time is that it neither teaches how to use OS/2 or how to develop OS/2 applications, nor is it a reference book. Instead, Inside OS/2 explains why the system was designed the way it was designed; in fact, Gordon Letwin was one of the very few people who could have written such a book, having worked as chief architect of systems software at Microsoft. Continue reading →

Posted in Books, Microsoft, OS/2 | 17 Comments

Phantom 3.0

Posted on July 13, 2012 by Michal Necasek

As previously mentioned, the OS/2 Museum adapted the Phantom redirector example from the second edition of Undocumented DOS to demonstrate that the redirector interface was already fully implemented in the August, 1984 release of PC DOS 3.0, a fact apparently unknown to most authors of DOS literature.

The Phantom 3.0 redirector is now available for download in the form of a 360K floppy image. Kudos to the authors of Undocumented DOS for writing it in the first place. Needless to say, the code is provided as is, and although bug reports are welcome, no promises are being made as to if or when any issues might be fixed. Continue reading →

Posted in Development, DOS | 36 Comments

MacBook Pro with Retina display: What a letdown

Posted on July 8, 2012 by Michal Necasek

I’ve been a satisfied user of MacBook Pro laptops since mid-2006, soon after the first Intel-based Macs appeared. My current system is a mid-2008 2.6 GHz 17″ MacBook Pro which I’ve been overall quite happy with. However, the Core 2 CPU is getting rather old (especially its virtualization capabilities are nothing to write home about) and what’s worse, upgrading the system beyond 4GB RAM is very problematic.

I’ve been eagerly anticipating the June 2012 refresh of the MacBook Pro line. I was very excited when I first heard about the MBPs with Retina display, having had a few months of experience with a Retina-equipped iPad. But when I started the inevitable pre-purchase research, my excitement turned into wariness and then severe disappointment. Here’s why… Continue reading →

Posted in Apple | 3 Comments

On a dark, rainy night in April 1985…

Posted on July 7, 2012 by Michal Necasek

Update: Since the original document disappeared, a local copy is now provided.

When researching the history of computing, from time to time an unexpected gem turns up. The copy of Ray Ozzie’s notes from a 1985 meeting with Microsoft is one of such gems.

Between 2006 and 2010, Ray Ozzie was the chief software architect at Microsoft, a role he took over from Bill Gates. But in the early 1980s, Ozzie worked at Lotus on the Symphony product, and in 1984 left Lotus to start a company called Iris Associates. Iris worked on a software project which (several years later) became known as Lotus Notes.

At the beginning of April 1985, Ray Ozzie (Iris) met with Microsoft in Bellevue, Washington (Microsoft moved to Redmond in early 1986). From the notes it is obvious that Iris had an unusual level of access; besides providing answers from managers and engineers, Microsoft also disclosed the bulk of its org chart as well as internal project scheduling data, including unannounced projects. Continue reading →

Posted in DOS, Microsoft, Windows | 39 Comments

Minor site updates and summer time

Posted on June 19, 2012 by Michal Necasek

Summer is upon us, and as a consequence, site updates will be less frequent in the coming weeks.

Regular visitors may have noticed that after a long delay, the DOS history article on DOS 4 was finally published. Researching DOS 4 (apparently known as DOS 3.4 right up to the actual release) turned out to be surprisingly difficult… although “a lot of work” may be more accurate than “difficult”. DOS 4 was released at a time when the PC market was well established, with fully developed trade press. That meant there were lots of sources talking about DOS 4.

At the same time, DOS 4 was less than wildly popular and many authors more or less ignored it. That made finding accurate information about DOS 4 difficult, although there were certainly lots of dubious rumors floating around. Continue reading →

Posted in Site Management | 5 Comments

Redirectors and DOS 3.0

Posted on June 3, 2012 by Michal Necasek

When attempting to determine when exactly the network redirector interface was introduced in DOS, the situation seems to be quite clear. Available literature agrees that DOS 3.1 (released in April 1985 by IBM, possibly earlier by Microsoft OEMs) was when redirector support was introduced. Advanced MS-DOS Programming says: “MS-DOS version 3.1, which was released in November 1984, added support for the sharing of files and printers across the network.” The Wikipedia article on PC DOS (as of May 30, 2012) claims that “Planned networking capabilities in DOS 3.00 were judged too buggy to be usable and Microsoft disabled them prior to the OS’s release.” The famous Ralf Brown’s Interrupt List (RBIL) documents redirector hooks (INT 2Fh/11h) as being called by the “DOS 3.1+ kernel”. Undocumented DOS (2nd Edition, page 494) mentions that “Microsoft has used the redirector interface since DOS 3.1”. Microsoft’s documentation for the MS-DOS CD-ROM Extensions 2.1 (MSCDEX) says that the “product uses the Microsoft Networks interface to MS-DOS so it requires MS-DOS version 3.1 or higher”.

It all seems very clear… except the above statements are either misleading or just plain untrue. The redirector interface was fully present in DOS 3.0, released in August 1984. Also included was the internal DOS services interface (INT 2Fh/12h), support for querying the SDA (Swappable Data Area), and minor other functionality related to networking. Continue reading →

Posted in DOS, Networking, PC history | 14 Comments

MS-DOS OAKs

Posted on May 25, 2012 by Michal Necasek

Prior to 1991, Microsoft did not sell MS-DOS to end users directly. Although MS-DOS 3.2 (1986) and later was available to system builders as a “packaged product”, most PC users would get an OEM version of MS-DOS with a new computer. Before 1986, that was the only way to get MS-DOS at all. Or DOS in general, if PC DOS is counted as a very special OEM version of MS-DOS. But where did the OEM versions come from?

Microsoft shipped DOS to OEMs in the form of the MS-DOS OEM Adaptation Kit, or OAK. The OAK consisted of binary files, source files, object files, and electronic documentation required to “install” MS-DOS on (or port to) an OEM platform. Over time, as the PC hardware was converging and DOS was evolving, the amount of code OEMs needed to adapt was getting smaller and the bulk of OEM versions of MS-DOS consisted of unmodified binaries provided by Microsoft. In fact Microsoft did not want OEMs to make significant changes, since Microsoft wanted to avoid unnecessary differences between various OEM releases of MS-DOS. Continue reading →

Posted in Development, DOS, Microsoft | 13 Comments

Early Microsoft Networks

Posted on May 18, 2012 by Michal Necasek

Microsoft networking technologies, often referred to as SMB and/or CIFS, have a very long history, longer than one might realize. While Microsoft’s networking products only became somewhat widespread around 1993-1994 with Windows for Workgroups, their history goes back to 1984-1985.

Microsoft Networks, or MS-NET, is tied to MS-DOS 3.0/3.1 and closely related to IBM’s PC Network Program, originally announced on August 14, 1984 (together with the PC/AT) and released on April 2, 1985 (together with PC DOS 3.1).

Thanks to the excellent ACT/Apricot website, some of the very early Microsoft networking products have come to light and can be examined. The following should be considered a work in progress and although the information presented here should be accurate, it is incomplete.

Continue reading →

Posted in DOS, Microsoft, Networking | 17 Comments