Woops, I read 'ISBNPrefix" but didn't think to check whether it was the .h or .cpp; the line I gave before was wrong, then.
ISBNPrefix.h is short, minus comments, so I'll post the whole thing.
>Why do you have code inside a .h file?
FILE* open(const char filename);
int isRegistered(FILE* fp, int area); //With comments in, this one's line 16
int minNoDigits(FILE* fp, int area);
int isRegistered(FILE* fp, int area, const char publisher);
int close(FILE* fp);
I don't, it's only (what's the term for placeholder function definitions, again?)s.
>Is stdio.h included BEFORE this file?
Should it be? That's probably my problem, right there.
Edit: Yeah, it was. Thanks!