c语言ispunct函数

#include <stdio.h>
#include <ctype.h>
int main ()
{
int i=0;
int cx=0;
char str[]="Hello, welcome!";
while (str[i])
{
if (ispunct(str[i])) cx++;
i++;
}
printf ("Sentence contains %d punctuation characters.\n", cx);
return 0;
}