1. CS-401 Computer Architecture & Assembly Language Programming
Lecture-10
Bit Manipulation

2. In the Last Lecture
We discussed
-Bubble sorting

3. Signed/unsigned numbers

4. Signed / Unsigned Numbers
Number Representation
x0002
xFFFE
; two’s compliment of ; decimal 65534

5. Signed / Unsigned Numbers
Example
mov ax, -2 ; ax = 65534
mov ax, 2 ; bx = 2
cmp ax, bx
ja label1 ; true! > 2

6. Signed / Unsigned Numbers
Example
mov ax, ; ax = 0xFFFE
mov ax, ; bx = 0xFFFE
; same representation
; different interpretation

7. Signed / Unsigned Numbers
Order and Range (16 – Bit)
Unsigned Numbers:
0<1<2<3<4 <………<65535
Signed Numbers:
-32768<-32767<…..<0<……<32767

8. Multiplication
x x 5 x
x x
x x x

9. Shift Instructions shr shift logical right shl shift logical left
sar shift arithmetic right
sal shift arithmetic left

10. Rotate Instructions rol rotate left rcr rotate through carry right
ror rotate right
rol rotate left
rcr rotate through carry right
rcl rotate through carry left

11. shr CF 1 1 1 1 1

12. shl CF 1 1 1 1 1

13. sal CF 1 1 1 1 1

14. sar CF 1 1 1 1 1 1 CF 1 1 1 1 1 1

15. ror CF 1 1 1 1

16. rol CF 1 1 1 1 1

17. rcr CF 1 1 1 1

18. rcl CF 1 1 1 1 1