4.2: (suggestion) Mention that implicit function declaration has been removed from the C spec

[alexeikm]

See this PDF (page 62), this might help programmers who are trying to refresh/improve their C knowledge through your book avoid such things.

Implicit declaration is mentioned in section 17.1, and although you've recommended against using it, saying that it's non-standard is more explicit, and putting this in Chapter 4 makes more sense imho.

[beejjorgensen]

Good ideas. Cleaned it up a bit in both places.