What programming language were written Mac OS Classic?
 

He that goes a little linux theme, but it's something I want to know.

The original Mac OS was written in Pascal. The current one is based on BSD Unix. What happened in between I don't know.

Well, one thing that happened in between is that Apple bought NeXT.

In Pascal?, I thought it was written in Objective-C, as they did was that if Pascal is a high level language?

My memory could be faulty---I mostly remember hacking something and discovering the difference in string handling between Pascal and C. Note that I was referring to the original Macs from the mid 80s.

I don't understand this

Yeah, I remember the conversion to Pascal strings when programming in C too, but most of the part was written in assembler according to the following link.

Great site about Mac’s history: folklore.org

The original MacOS indeed was done in Pascal. The OS/X project was done in Objective-C.

As an aside... if you have not yet encountered both of these languages, you should definitely make it your business to do so. (Because, well, this sort of know-how is "your business!")