in 00
sub al, 30
mov [b0], al    ;put n1 into [20]

in 00
mov [b1], al    ;put op into [21]

in 00
sub al, 30
mov [b2], al    ;put n2 into [22]

mov al, [b1]    ;mov op into al

cmp al, 2b  ;is op plus
jz plus

cmp al, 2d
jz minus

cmp al, 78
jz mult

cmp al, 2f
jz div

jmp fin

plus:
    mov al, [b0]    ;mov n1 into al
    mov bl, [b2]    ;mov n2 into bl
    add al, bl
    add al, 30
    mov [c0], al    ;mov sum into vdu
    jmp fin
minus:
    mov al, [b0]    ;mov n1 into al
    mov bl, [b2]    ;mov n2 into bl
    sub al, bl
    add al, 30
    mov [c0], al
    jmp fin

mult:
    mov al, [b0]    ;mov n1 into al
    mov bl, [b2]    ;mov n2 into bl
    mul al, bl
    add al, 30
    mov [c0], al
    jmp fin
div:
    mov al, [b0]    ;mov n1 into al
    mov bl, [b2]    ;mov n2 into bl
    div al, bl
    add al, 30
    mov [c0], al
    jmp fin


fin:
end