Pascal is one of my least favorite languages, but reading about how compilers work and examining real code of the (actually fairly simple) system works is fun. Check out:
Included here is the Pascal source of a public-domain Pascal compiler and interpreter, the P4 compiler and interpreter. It is coded entirely in Pascal, and produces a high-level so-called intermediate code as output. The program 'pint' is an assembler and interpreter for this language.
The complete text of the book explaining the compiler is also available.