MS-DOS 4.0 (multitasking)
multitasking operating system
MS-DOS 4.0 was a multitasking release of MS-DOS developed by Microsoft based on MS-DOS 2.0. Lack of interest from OEMs, particularly IBM (who previously gave Microsoft multitasking code on IBM PC DOS included with TopView), led to it being released only in a scaled-back form. It is sometimes referred to as European MS-DOS 4.0, as it was primarily used there. It should not be confused with PC DOS 4.00 or MS-DOS 4.01 and later, which did not contain the multi-tasking features.
History
Apricot Computers pre-announced "MS-DOS 4.0" in early 1986, and Microsoft demonstrated it in September of that year at a Paris trade show. However, only a few European OEMs, such as SMT Goupil and International Computers Limited (ICL), actually licensed releases of the software. In particular, IBM declined the product, concentrating instead on improvements to MS-DOS 3.x and their new joint development with Microsoft to produce OS/2.
As a result, the project was scaled back, and only those features promised to particular OEMs were delivered. In September 1987, a version of multi-tasking MS-DOS 4.1 was reported to be developed for the ICL DRS Professional Workstation (PWS). This ICL/MS MS-DOS 4.10.20 version was released on October 28, 1987.
“MS-DOS 4.0 (multitasking)” enters the record as multitasking operating system. Crown Archives preserves that source wording while asking what MS-DOS, multitasking and operating can confirm, complicate or overturn.
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Named sources, stable identifiers and responsible institutions provide the strongest route from overview to verifiable evidence. The source revision retrieved here is dated Aug 18, 2026. The linked authority identifier is Q17146052. None of the 1 selected statements returned an explicit reference. The first chronological checks are 1986 and 1987.
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This entry incorporates text from “MS-DOS 4.0 (multitasking)” on English Wikipedia. Contributors are listed in the page history. Text is available under the Creative Commons Attribution-ShareAlike 4.0 License. Selected authority identifiers and statements are retrieved from Wikidata under CC0; their references and qualifiers remain part of the verification path.