An external variable must have only one definition, but can have many declarations. Once declared, a structure is just like a data type. A structure variable must be to the left of a . C reads and writes streams of characters. In a macro that takes arguments, surround every substitution of the argument with parentheses and the entire macro with parentheses.
Conditional compilation is the best way to segregate non-portable code.
All typedefs are evaluated by the compiler.