int isgraph(int chr);

checks for any printing character except space (' ')

#include <iostream> /* including standard library */
#include <string>
#include <cctype>
 
using namespace std;
int main ( void )
{
  int i;
  string str="Test\n-!&%1";
  for (i=0; i <= 11;i++)
    {
     if ( isgraph(str[i]) != 0 )
      {
       cout << "Character " << i << " is a graph" << endl;
      }
    }
  return 0;
}

  output:
  Character 0 is a graph
  Character 1 is a graph
  Character 2 is a graph
  Character 3 is a graph
  Character 5 is a graph
  Character 6 is a graph
  Character 7 is a graph
  Character 8 is a graph
  Character 9 is a graph