isupper—uppercase character predicate #include <ctype.h>
int isupper(int c);
Description
isupper is a macro which classifies ASCII integer values by table
lookup. It is a predicate returning non-zero for uppercase letters
(A–Z), and 0 for other characters. It is defined only when
isascii(c) is true or c is EOF.
You can use a compiled subroutine instead of the macro definition by
undefining the macro using `#undef isupper'.
Returns
isupper returns non-zero if c is a uppercase letter (A-Z).
Portability
isupper is ANSI C.
No supporting OS subroutines are required.