>      void
>      DELAY(unsigned int us);

> so what "use as an expression" are we talking about?  You can't use
> void functions as expressions, can't you?

You can in some contexts.  You can as the left-hand operand of a comma
operator, as the second or third operand of a ?: (when the other one is
also void, at least), and as the expression part of an
expression-plus-semicolon statement.  The first and third pieces of a
for-loop control are other such contexts.

Basically, the only thing you _can't_ do with an expression of type
void is actually use its value.

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