Multitasking MS-DOS 4.00 4.x

Multitasking "MS-DOS 4.00" is a developmental version of MS-DOS that was never released to retail consumers. It was eventually licensed to some companies for internal use. Development started in parallel during the DOS 2.x days, and was intended to be the successor to MS-DOS 3.x. It would have competed against Digital Research's Concurrent DOS.

Microsoft shelved the product in favor of OS/2. However as OS/2 adoption was slow, IBM extended the existing MS-DOS 3.x to create IBM's DOS 4.0x, which Microsoft released as the actual MS-DOS 4.00 product.

As such, Multitasking MS-DOS 4.00 and the actual MS-DOS 4.00 release are not directly related.

Multitasking MS-DOS Version 4.00 (5.25).7z,0.17 MB
Multitasking MS-DOS Version 4.00 (Beta 5-29-84) (5.25-360k).7z,107.70 MB