;program to test SUB instruction
;on the first instruction, 1 is subtracted from the accumulator,
;making it -1 (since the accumulator starts as 0).
;on the next instruction the program halts

00 NUM 0
01 SUB 3 ;subtract the number at line 3 from the accumulator
02 STP   ;halt program
03 NUM 1 ;the number to be subtracted from the accumulator is 1