>>24
In the early days, Mac Classic was largely written in assembler. Applications were often written in Pascal, but also often assembler or C. HyperCard is an example of a C program from that era. After the switch from 68K to PPC, Apple started converting the assembler to C. There was probably 68K assembler in Mac OS 9, since Apple shipped its PPCs with a very nice emulator.
It seems like it was written in Pascal because the OS used interfaces and calling conventions that often matched Pascal. Most of the syscalls were just illegal instructions trapped by the OS, and passed parameters in registers, which is NOT Pascal-friendly (or C-friendly, for that matter).