Example of String Character Access

   // C++ strings can be used like array of characters 
   // for access and assignment ...
   string strA = "123456789";
   char a = strA[5];                // value '6'
   strA[3] = 'x';                   // value "123x56789"

   // Alternatively the at function can be used ...
   strA = "123456789";
   a = strA.at(5);                  // value '6'
   strA.at(3) = 'x';                // value "123x56789"