isupper.c

标准c库代码,可以应用于各个系统提供了大量的基本函数

/*
FUNCTION
<<isupper>>---uppercase character predicate

INDEX
isupper

ANSI_SYNOPSIS
#include <ctype.h>
int isupper(int <[c]>);

TRAD_SYNOPSIS
#include <ctype.h>
int isupper(<[c]>);

DESCRIPTION
<<isupper>> is a macro which classifies ASCII integer values by table
lookup.  It is a predicate returning non-zero for upper-case 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 upper case letter (A-Z).

PORTABILITY
<<isupper>> is ANSI C.

No supporting OS subroutines are required.
*/
#include <_ansi.h>
#include <ctype.h>

#undef isupper
int
_DEFUN(isupper,(c),int c)
{
	return((_ctype_ + 1)[c] & _U);
}