10. Stack Machine Example

• Each command needs to print detailed information about its particular execution step. For example, the source program

      push 123
      push 456
      add
      add
      hlt
      start
  

  should generate the following (or similar) output as a result of the execution:

      1.  PUSH 123
      2.  PUSH 456
      3.  ADD  456 + 123 = 579
      4.  ADD  579 + *** ERROR: THE STACK IS EMPTY
  

• The first column displays an imaginary program counter. This can be either a sequential number or an actual address of the command in memory.