In 1989, I got a well-used copy of the Official GEOS Programmer's Reference Guide (which I call OGPRG) & geoProgrammer. Due to critical errors in OGPRG & sample source code files, I've been wanting a single reference as complete & correct as the C64PRG ever since, knowing the only way I'll get one is if I write it myself. I've wanted to for 30 whole years. Now it's consuming me, & when I'm done I'll probably know the OS inside out.