sample1.txt 
   Tests the indexed load instructions.
   Prints two tables, one of A-Z, the other of 1-10.

sample2.txt
   Tests the call/ret instructions.
   Prints a face where the lines are printed using subroutine calls.

sample3.txt 
   Tests the int/iret instructions.
   The main loop is printing the letter A followed by a number
   that is being periodically incremented by the timer.
   The number will increment faster if the timer period is
   shorter.

sample4.txt
   Tests the proper operation of the user stack and system
   stack, and also tests that accessing system memory in 
   user mode gives an error and exits.

sample5.txt
   This is one you should create.  Be sure to include comments 
   so the grader knows what the program is doing.