No book. Just one course. I was a rather humble support guy for COBOL applications, so I had to learn COBOL, which I did. I was sent by my manager for a one-o

No book. Just one course. I was a rather humble support guy for COBOL applications, so I had to learn COBOL, which I did. I was sent by my manager for a one-off, three-day "advanced COBOL" course. It wasn't about advanced COBOL; it was an advanced course on the seven-pass Burroughs COBOL compiler. Memory was short in those days, hence the seven passes; intermediate results were files on disk. We learned that by nulling the executable for a chosen pass, we could hack the intermediate files, to do things COBOL programs weren't supposed to do, like calling OS functions. I learned how parsers work, and how parse trees are represented. I learned about intermediate code, optimisers, interpreters, and code generators. I got interested in compilers, and wrote a source-level debugger. It was just a three-day course, but it was incredibly valuable to me. Perhaps life-changing. Perhaps it's not so much that that course made something click that wasn't clicking for me; rather, it inspired an interest in me that simply wasn't there before. As I said this was a one-off course. There was about seven of us, and I don't believe anyone else ever received that training.