An exceedingly powerful programming environment, influenced by Unix yet not wholly like. Not as bad as DOS, often not as good as Unix (although sometimes much better, it is what the true hacker wants to use. And it's free, wh. means the hacker&can actually use it.

I have been recently using it to write a homebrewing program in C++. It's been quite a learning experience. I advise any MacOS programmer to try it out.