toupper—translate characters to uppercase #include <ctype.h>
int toupper(int c);
int _toupper(int c);
Description
toupper is a macro which converts lowercase characters to uppercase,
leaving all other characters unchanged. It is only defined when
c is an integer in the range EOF to 255.
You can use a compiled subroutine instead of the macro definition by
undefining this macro using `#undef toupper'.
_toupper performs the same conversion as toupper, but should
only be used when c is known to be a lowercase character (a–z).
Returns
toupper returns the uppercase equivalent of c when it is a
character between a and z, and c otherwise.
_toupper returns the uppercase equivalent of c when it is a
character between a and z. If c is not one of these
characters, the behaviour of _toupper is undefined.
Portability
toupper is ANSI C. _toupper is not recommended for portable programs.
No supporting OS subroutines are required.