3. General State Handling Logic

• 
  #include <iostream>
  using std::stream;
  int main()
  {
      int value = 0;
      cin >> value;
      if ( !cin ) {
          // cin is not good, more checks required:
          if ( cin.bad() ) {
              // cin is corrupted
              return 1; // signal error back to the operating system
          }
          if ( cin.eof() ) {
              // nothing to do: we want all inputs to end like this!
              return 0; // signal success to the operating system
          }
          if ( cin.fail() ) {
              cin.clear(); // prepare for more input...
              // do something to recover...
          }
      }
      // use value, everything is ok
      return 0;
  }