"Multitasking" MS-DOS 4.00
---

This was first unearthed copy of Microsoft's "multitasking" version of MS-DOS.  It's since been copied
to other web sites, but these are the original images, released on [jsmachines.net](http://jsmachines.net/)
in March, 2013.  This version of MS-DOS was never officially released in North America.  More information
is available at [Wikipedia](http://en.wikipedia.org/wiki/Multi-tasking_MS-DOS_4.0) and
[OS/2 Museum](http://www.os2museum.com/wp/?p=1769).

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, released in June, 1988. 

The [IBM Model 5160](/configs/pc/machines/) 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](/configs/pc/machines/5160/cga/640kb/dos400m/ "PCjs:ibm5160:::debugger")