int ispunct(int chr);

tests whether a character is punctuation mark

#include <stdio.h> /* including standard library */
//#include <windows.h> /* uncomment this for Windows */
 
#include <ctype.h>
 
int main ( void )
{
  int i;
  char string[11]="Test -!&%1";
  for (i=0; i <= 11;i++)
    {
     if ( ispunct(string[i]) != 0 )
      {
       printf("Character %i is a punctuation mark\n",i);
      }
    }
  return 0;
}

  output:
  user@host:~$ ./ispunct 
  Character 5 is a punctuation mark
  Character 6 is a punctuation mark
  Character 7 is a punctuation mark
  Character 8 is a punctuation mark