Just about every language is written in C. Even GW-BASIC was written in C (most BASIC interpreters were written in assembly code at the time).
When all the code was being rewritten for Y2K, C was used because it was really the only language that was portable at the time, you could write the program on a PC, and then compile and configure it on a mainframe, or vice versa.
A more pertinent question would be what isn’t wriiten in C.
Critical software, like interfaces, machine operation or database systems, are generally not written in C. That’s because C code can be dense and obscure. If the original programmer retire or goes missing, and the system crashes, no one else may have a clue what they’ve actually coded. So a more explicable, higher level language is used and C is quarantined to use in system software where its power and access is useful.
Just about every language is written in C. Even GW-BASIC was written in C (most BASIC interpreters were written in assembly code at the time).
When all the code was being rewritten for Y2K, C was used because it was really the only language that was portable at the time, you could write the program on a PC, and then compile and configure it on a mainframe, or vice versa.
A more pertinent question would be what isn’t wriiten in C.
Critical software, like interfaces, machine operation or database systems, are generally not written in C. That’s because C code can be dense and obscure. If the original programmer retire or goes missing, and the system crashes, no one else may have a clue what they’ve actually coded. So a more explicable, higher level language is used and C is quarantined to use in system software where its power and access is useful.