3.10 isupper—uppercase character predicate

Synopsis

     #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.