I can't quite pin it down, but reading this and similar works I am reminded you have to be distinctly non stupid to follow lines of reasoning in these books, at some level. You have to bring inductive reasoning to bear on what is laid out. It's teaching by doing. You have to do the syntax and BNF reasoning for yourself.<p>It's pedagogy but demands competency. I always struggled with this. Few of my peers, who had competency in bucketloads would agree with me.<p>I just put into the discard pile the first CS book I bought new for my 1st year pascal course in 1979, it's typeset in as much as a monotype typewriter used as output device is. (The Fortran and algol I did in the mid 70s used badly photocopied handout notes)<p>Its also by Wirth, who had (if i recall correctly) just finished a residency at York working on the modula/II proposal, and subsequently his Ada proposal(s). He seemed to like the same language, reprising it syntactically time after time. After I learned C I never went back to pascal or it's derivatives.