Recently, Microsoft published the source code of old MS-DOS versions on Github: https://github.com/Microsoft/MS-DOS

What is odd in my opinion is the use of x86 assembly language for everything. The assembly language would not be my first choice for implementing an operating system. At the time MS-DOS was created, the C programming language had already been invented in Bell Labs, offering a good compromise between low level and high level programming.

Was this assembly language approach used also in the newest versions of MS-DOS in the 1990s?

Recently, Microsoft published the source code of old MS-DOS versions on GitHub.

What is odd in my opinion is the use of x86 assembly language for everything. The assembly language would not be my first choice for implementing an operating system. At the time MS-DOS was created, the C programming language had already been invented in Bell Labs, offering a good compromise between low level and high level programming.

Was this assembly language approach used also in the newest versions of MS-DOS in the 1990s?