I like to talk about this in my CS classes. We get compiles to compile code by compiling a compiler with a compiler. It’s an infinite regression problem that terminates with someone writing a compiler in assembly… Which requires an assembler to assemble… So you write an assembler in machine code directly on the processor.

If we lost all of the currently compiled programs one day, even with the compiler source code in hand, it would be some serious work to rebuild our current tool chains.