I think that the early versions of the Pascal compiler were writen so as to be bootstrappable on diverse systems. I believe you had to write a simple virtual ma

I think that the early versions of the Pascal compiler were writen so as to be bootstrappable on diverse systems. I believe you had to write a simple virtual machine to bootstrap the compiler. I cannot find a source for that, I heard it in compilers course. This was more of a necessity than something done for verifiability though. Systems were more diverse back then and you couldn't just target "a Unix with a C compiler".