            segment .data
    a       dq      100
    b       dq      200
    diff    dq      0
            segment .text
            global  main
    main:
            push    rbp
            mov     rbp, rsp
            sub     rsp, 32
            mov     rax, 10
            sub     [a], rax    ; subtract 10 from a
            sub     [b], rax    ; subtract 10 from b
            mov     rax, [b]    ; move b into rax
            sub     rax, [a]    ; set rax to b-a
            mov     [diff], rax ; move the difference to diff
            xor     rax, rax    ; was "mov   rax, 0"
            leave
            ret