Know how to declare a function that takes no arguments, and how to declare a function that returns no value.
The keyword "static" has multiple (and sometimes unexpectedly different) uses. Know what it means when applied to a global variable declaration, a function declaration, and the definition of a variable within a function.
Know what the keyword "register" means.
Know how to define and initialize (in one statement) simple arrays. Do you always need to specify the array size?
Understand what's different about initializing character arrays. Be able to produce the full syntax for initializing a character array both with and without the use of a string constant.
Understand how to define a variable in one file, and declare (and use) it in another file.