Ten years after the source code for MS-DOS 1.25 and 2.0 was opened, Microsoft announced the release of the source code for the MS-DOS 4.0 operating system, originally released in 1988 and developed in collaboration with IBM. The code is open under the MIT license, which allows modifications, distribution, and usage in products. In addition to the code, documentation and disk images are available in the public domain.
The product is written in assembly language for 8086 processors. Emulators such as PCem and 86box can be used to run it. The release of MS-DOS 4.0 is notable for its support for a graphical interface and mouse, the ability to handle disk partitions larger than 32 MB (up to 2 GB), the addition of the DOSSHELL file manager, support for EMS (Expanded Memory Specification), and commands FASTOPEN and FASTSEEK.
Source: opennet.ru
