Question

Here is my code fragment:

    .data
Num1    equ     40h
Num2    equ     41h
Var1    dword   0
Var2    dword   0
;----------------------------------------------------------------------
    align   4
    .code       ;insert executable instructions below
main    PROC        ;program execution begins here
    mov Var1, Num1
    mov Var2, Num2

    add Var1, Var2

I am trying to use the ADD instruction but I get the following error:

error A2070: invalid instruction operands

This error is related to the ADD line.
If I omit that line the program runs fine.

Answer 1

You can’t add two memory location to each other, you should use one of the registers as a second operand

 .data
Num1    equ     40h
Num2    equ     41h
;----------------------------------------------------------------------
    align   4
    .code       ;insert executable instructions below
    main    PROC        ;program execution begins here

    mov ax, Num2

    add ax, Num1