Note:
   Output is worth 40 points.
   Each of these is worth 8 points of output.

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
   Calculates sum from i=1 to i=n of n, where n is the value stored
   at address 500.