I am open to recommendations as to: What textbook would be good? What compiler(s) are available in Ada for modification? Definately take a look at Crafting a Compiler, by Fisher & LeBlanc. They actually have as a running example building a language that is a subset of Ada 83. (Note that there's another, similarly named book, called Crafting a Compiler in C. The authors re-wrote the examples in C, instead of the Ada-like syntax of the earlier version.) There are a couple of other books aren't as heavy on the theory (a good thing, methinks). Check out: Compiler Design in C Allen I. Holub Writing Compilers and Interpreters Ronald Mak I couldn't really make sense of the Dragon book. I have no idea why that book is so popular. To modify a compiler, you could use GNAT. The sources are freely available from NYU. I know you can buy the source in the Holub book from the author (US$80 last time I inquired).