Q1: Why does my program go into an endless loop after the prompt to enter seat 
    assignment?



Q1: Why does my program go into an endless loop after the prompt to enter seat 
    assignment?

A1:
1) Comment out your error checking in fill_seats() to allow correct input to 
be entered.

2) Cleanup fill_seats()
   a) Allow user to enter single character
   b) Assign into tmp_seat
   c) If lowercase convert to uppercase  ( a --> A,   x --> X )
   d) Use a switch statement on j  "switch ( j ) 
                                    {  case 0:
                                            if ( tmp_seat !=  ... )
                                    }
After you do the above, you will be able to see the logic more clearly