Question

In what language was MSDOS originally written in?

The Wikipedia Article implies either C, QBasic or Pascal, but:

• C was invented to write UNIX, so I don’t believe it was used to write MSDOS
• Pascal seems popular to teach programming, but not really popular to write Operating systems in
• QBasic didn’t seem to be very popular for Operating Systems at the time MSDOS was developed (or was *BASIC ever very popular to write Operating Systems in it?)

Except these three languages there is also Assembly, but I assume that Microsoft already switched from Assembly to a “higher” level language?

Since C was originally invented for UNIX, I still wouldn’t think Microsoft is using C… although the Microsoft API is written in C (I find this kind-of oxymoronic, actually).

Can anyone enlighten me on this topic?

Answer 1

http://answers.google.com/answers/threadview?id=197874

Since CP/M was written in FORTRAN and
QDOS was based on CP/M, does it mean
that QDOS and MS-DOS were written in
FORTRAN? According to our next
article, written by Tim Patterson
himself, the assembly language used by
Seattle Computer Products wasn’t
FORTRAN but was built in-house since
it was the only thing available to
them at that time.

“The last design requirement was that
MS-DOS be written in assembly
language. While this characteristic
does help meet the need for speed and
efficiency, the reason for including
it is much more basic. The only 8086
software-development tools available
to Seattle Computer at that time were
an assembler that ran on the Z80 under
CP/M and a monitor/debugger that fit
into a 2K-byte EPROM (erasable
programmable read-only memory). Both
of these tools had been developed in
house.”

“An Inside Look at MS-DOS”
http://www.patersontech.com/Dos/Byte/InsideDos.htm