int main()
{
  int j = 0;
  cout << "Please enter a number to calculate: ";
  if(!(cin >> j))
    cout << "You must enter a number!" << endl << endl;

  else
    cout << "You entered " << j << endl << endl;
}

// declare function prototype
void InputChecker();

int main()
{
  InputChecker();
} // end main


void InputChecker()
{
   // collect input
   if(!(cin >> j)) // test input
  {
    // do something
    InputChecker();        // recursive function call
  }
    else
    // do something else

} // end InputChecker

/*
   Project Software Engineer
      Mr Gregory Hicks BIT
        Sydney Australia
           (C) 2006
        
   This code may be used provided
   credit is given for the source
*/

#include <cstdlib>
#include <iostream>

using namespace std;

int  getUserInput ( const char* msg , const int  min , const int  max , const int  quit );
char getUserInput ( const char* msg , const char min , const char max , const char quit );

int main(int argc, char *argv[])
{
    int t =  getUserInput ( "Enter an integer" , 0 , 10 , -1 );
    if ( t != -1 )
      cout << " Integer entered is: " << t << endl;
      
    char c = getUserInput ( "Enter a letter" , 'A' , 'z' , '0' );
    if ( c!= '0' )
      cout << "Letter entered is: " << c << endl;
      
    system("PAUSE");
    return EXIT_SUCCESS;
}

/*
   Purpose: To get an integer input from the user
   Accepts: msg - display message
        Min - smallest acceptable value
        Max - largest acceptable value
        quit - vaue to force quit on return
*/
int getUserInput (  const char* msg , const int  min , const int  max , const int quit  )
{
    int input;
    
    do {
        cout << msg << " (Range: " << min << " to " << max << " , quit= " << quit << "): ";
        cin >> input;
    } while ( input != quit && ( input < min || input > max ) );
    return input;
}

/*
   Purpose: To get a char input from the user
   Accepts: msg - display message
        Min - smallest acceptable value
        Max - largest acceptable value
        quit - vaue to force quit on return
*/
char getUserInput ( const char* msg , const char min , const char max , const char quit )
{
    char input;
    
    do {
        cout << msg << " (Range: " << min << " to " << max << " , quit= " << quit << "): ";
        cin >> input;
    } while ( input != quit && ( input < min || input > max ) );
    return input;
}