It is very difficult or nearly impossible to build an OS kernel in Fortran. The reason is that it uses a memory management model that doesn't do well with pointers, and is highly static. There are rare exceptions, I think the PrimOS kernel was mostly in Fortran with a little bit of assembly. But just because it was done once doesn't mean it is a good idea.Was Fortran or Ada ever suggested for base system alongside C.
For user-level applications, Fortran is perfectly viable.
I keep retelling the same story: When VMS shipped, the OS development group made sure that for every language that is officially supported by DEC, at least one of the base OS utilities is written in that language. That's to make sure that all runtime libraries for all languages are shipped and installed with the base OS. Fortran was not a problem at all; the fun one was RPG-II (which is usually a batch processing report generation language); with considerable effort, the monitor utility (sort of the equivalent of ps, top, df and similar tools) was written in RPG-II.
See above. It could be used, if someone wanted to use additional languages. There are certain things that it is very good at. Fortran code tends to execute faster, for a variety of minor reasons (no modifiable parameters, no pointers, easy to use single-precision floating point, the optimizer can do memory placement without worrying about pointers or aliasing).Re Fortran, it's not enough that the programming language exists, there needs to be an argument to use it... what does it offer that C does not have?