14. Additional Features and Improvements

• This is an open-ended project. The possibilities are endless when considering other useful commands and features.

• Level difficulty I (easy, 5 xtra pts awarded for each feature):

  • Add arithmetic commands SUB, MUL, DIV, and MOD (modulus, or remainder of the division).

  • Add a CMP command to compare the operand with the value on top of the stack. Compute the difference and push the result on the stack:

        cmp 0
    

• Level difficulty II (advanced, 15 xtra pts each):

  • Add a fixed number of register-like variables (e.g. EAX, EBX, ECX, EDX, ...) available to the stack machine programmer.

  • Add new commands that work with variables:

        push 123
        pop  eax
        push eax
        pop  ebx
    

  • Add program comments, for example,

        ; This is a comment
    

    The comments should be handled by the text input parser, thus not requiring any changes in the stack machine code.

• Level difficulty III (most difficult, 25 xtra pts):

  • Consider adding code labels and a jump command:

        push 10
        push 20
        push 30
      label:
        add
        jmp label
    

    The above fragment computes the sum (10+20+30) and terminates as soon as the stack becomes empty.

  • Once basic jump mechanism is in place, conditional jumps can be added, as well as the subroutine CALL and RET commands.