1. CS-401 Computer Architecture and Assembly Language Programming
Lecture-6
Addressing Modes

2. Lets revise the last lecture

3. Memory Access Size

4. Memory Access Forms
16-bit Move
mov ax, [num1]

5. Memory Access Forms
8-bit Move
mov al, [num1]

6. Memory Access Forms Illegal Move mov ax, bl ; size mismatch
mov [num1],[num2] ; mem to mem move

7. Memory Access Forms Ambiguous Move
mov [num1], 5 ;5 is byte or ;word? Ambiguous
mov byte[num1], 5 ;move 5 as byte
mov word[num1], 5 ;move 5 as word

8. Loop Control L1: mov ax, bx add bx,2 sub cx,1…
L1: mov ax, bx
add bx,2
sub cx,1
jnz L1 ; Jump to location L1
; if the zero flag is ; not set

9. Loop Control mov cx, 10 ; load numbers count…
mov bx, num1 ; point bx to first number
mov cx, ; load numbers count
add ax, [bx] ; add number pointed by bx to ; ax
l1: add bx, 2
sub cx, 1
jnz l1
mov [num1+20], ax ; write back result
num1: dw 5…