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Multitasking MS-DOS 4.00

These disk images contain the first unearthed copy of Microsoft's "multitasking" version of MS-DOS. They were were discovered by the PCjs Project in March 2013. This version of MS-DOS was never officially released in North America. More information is available at Wikipedia and OS/2 Museum.

Note: The designation "4.0M" is not an official version number; it's an internal version number used only to differentiate these disk images from those of the official MS-DOS 4.00 release in July 1988.

The IBM Model 5160 machine configuration below boots MS-DOS 4.0M. To access the MS-DOS "Session Manager" after it's booted, tap the Alt key.

IBM Model 5160

Waiting for PCjs to load