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blog:pushbx:2025:0501_ms-dos_v3.40_versus_v4.00

MS-DOS v3.40 versus v4.00

I have recently referred to the "v3.40 branch" of MS-DOS. This refers to the v4.00 and v4.01 versions that are well known and that have shipped most sources in the 2024 April release.

The v3.40 distinction is as opposed to the "European MS-DOS v4.00", "Multitasking MS-DOS", or the "v4.00 Ozzie" version. This one unfortunately lacks most of its sources.

Now, where does "v3.40" come from? There are two sources of this term:

The "DOS34" flag

This is a variable in the DOS Swappable Data Area called the DOS34_FLAG. The comment calls it "common flag for DOS 3.4". (The values for this word are given in the file devsym.mac.)

In the Interrupt List's list of the MS-DOS v4 SDA, it is called "DOS 3.4 (European MS-DOS 4.00) bit flags". For one, this indicates that the "DOS 3.4 flags" term leaked in some way to be incorporated into the Interrupt List before the release of the sources.

For another, I think it's mistaken about the "European MS-DOS v4.00" bit. I think MS-DOS v3.40 was a term for the regular (non-multitasking) MS-DOS branch that was eventually released as v4.00. This is specifically in opposition to the "European" branch.

The special entries list

The version fake table, or special entries list, is the MS-DOS v4.00 incarnation of what later became SETVER. Interestingly, the faked version number in the default list is always the 3.40 version. So it stands to reason that v3.40 was considered the successor of v3.20, v3.30, or v3.31.

So what?

I believe that v3.40 may have been the name for the branch that became the non-multitasking v4.00 while the multitasking v4.00 probably started out as the original "v4", the idea being that it was a crass departure from the v3 branch while v3.40 was a continuation with fewer differences (such as the support for 32-bit sector numbers, hash buckets for buffers, and the Extended Open/Create system call).

Discussion

E. C. MaslochE. C. Masloch, 2025-05-05 19:00:53 +0200 May Mon

Here's two quotes from the OS/2 Museum page. First from a 2012-06-19 announcement:

Researching DOS 4 (apparently known as DOS 3.4 right up to the actual release) turned out to be surprisingly difficult…

Minor site updates and summer time | OS/2 Museum

And from the MS-DOS v4.00 history article that is linked by the announcement:

While in development, DOS 4.0 was known as DOS 3.4. In retrospect, version 3.4 might have been more accurate for the DOS kernel, but the entire package with the DOS Shell, large disk support, and a new installer probably deserved a new major version number.

DOS 4.0 | OS/2 Museum

E. C. MaslochE. C. Masloch, 2025-05-07 09:35:58 +0200 May Wed

Here's a quote from the article on MS-DOS v4.xx from betaworld.cn:

MS-DOS 4.00于1988年7月发布。该版本最初被命名为“MS-DOS 3.40”。这一名称在1987年8月微软与Zenith Data Systems签订的合同以及1988年9月的塞尔维亚计算机杂志《Svet Kompjutera》中均有提及。由于MS-DOS 4.00的外壳和内存管理系统中存在严重bug,该版本在1988年11月被MS-DOS 4.01取代。 (请注意不要和Multitasking MS-DOS 4搞混) MS-DOS 4.x - BetaWorld

Translated using Google Translate:

MS-DOS 4.00 was released in July 1988. This version was originally named "MS-DOS 3.40". This name was mentioned in the contract signed between Microsoft and Zenith Data Systems in August 1987 and in the Serbian computer magazine "Svet Kompjutera" in September 1988. Due to serious bugs in the shell and memory management system of MS-DOS 4.00, this version was replaced by MS-DOS 4.01 in November 1988. (Please note that it should not be confused with Multitasking MS-DOS 4)

E. C. MaslochE. C. Masloch, 2025-05-07 13:38:24 +0200 May Wed

The reference to Svet Kompjutera seems to refer to this blurb on page 4 of the 1988 September issue: (Transcribed by me, some of the letter choices may be wrong.)

MS-DOS 3.4

Microsoft če u toku ove godine izbaciti na tržište MS-DOS 3.4. Radi se o sasvim novoj verziji operativnog sistema što se najviše ogleda u grafički orijentisanom korisničkom interfejsu. Medutim postoji problem u vezi sa oznakom "3.4". Oznaka MS-DOS 4 več je koriščena u Velikoj Britaniji, a MS-DOS 5 je zaštitno ime za razvoj OS/2. Tako su u Microsoftovom timu na velikoj muci.

D.T.

Svet Kompjutera 1988 September

Translated using Google Translate:

MS-DOS 3.4

Microsoft will release MS-DOS 3.4 this year. It is a completely new version of the operating system, most notably in its graphical user interface. However, there is a problem with the "3.4" designation. The MS-DOS 4 designation is already in use in the UK, and MS-DOS 5 is a trade name for the development of OS/2. So the Microsoft team is in a big trouble.

D.T.

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blog/pushbx/2025/0501_ms-dos_v3.40_versus_v4.00.txt · Last modified: 2025-05-01 18:00:11 +0200 May Thu by ecm