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toupper
[translate characters to upper case]

SYNOPSIS
#include <ctype.h>
int toupper(int c);
int _toupper(int c);

DESCRIPTION
toupper is a macro which converts lower-case characters to upper case, 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 upper-case 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.

COMPLIANCE
toupper is ANSI C. _toupper is not recommended for portable programs.

No supporting OS subroutines are required.