Download MULTIPLICATION AND DIVISION INSTRUCTION (1)

1
Lab Manual CSC159
1.4
MULTIPLICATION AND DIVISION INSTRUCTION
i.
MUL
The MUL instructions multiply an 8-bit or 16-bit operand by AL or AX.
If an 8-bit source operand is supplied, it is automatically multiplied by AL,
and the result is stored in AX.
If a 16-bit source operand is supplied, it is multiplied by AX , and the
result is stored in DX and AX (the high 16 bits are in DX).
Syntax:
MUL
source
The source operand may be either a register or a memory operand, bit it
may not be immediate data. The destination (either AX or DX:AX ) is
implied and may not be changed.
Example 1: 8 bit register data
Mul CL
If AX register consist value of 451416 and the content of CL register is 0516, after this
instruction is executed, the content of register AX will be 006416.
AX
45
14
AH
AL
CX
05
CH
CL
Mul CL
AX
00
DH
64
DL
2
Lab Manual CSC159
How to calculate:
AX
AH
AL
1416 =
0001 0100
0516 =
101
0001 0100
+
0 0000 000
00 0101 00
0000 0000 0110 0100
0
0
6
4
Example 2. Multiply AL by 10h:
Mov
Mov
Mul
AL , 6h
BL, 10h
BL
How to calculate:
;AX = 0060h
AX
AH
AL
1016 =
1 0000
0616 =
110
0 0000
10 000
+
100 00
110 0000
6
0
3
Lab Manual CSC159
Example 1: 16 bit register data
Mul CX
If AX register consist value of 763416 and the content of CL register is 0716, after this
instruction is executed, the content of register AX will be 3B6C16, while the content of
DX register will be 000316.
AX
76
34
AH
AL
CX
07
CH
CL
Mul CX
AX
3B
6C
AH
AL
DX
00
DH
03
DL
4
Lab Manual CSC159
How to calculate:
AH
DH
AL
DL
3
2
7
1
6
1
3
4
7
51
3
16 √51
48
3
000 3
3
43
22
28
2
1
1
16√43 16√22 16√28
32
16
16
11
6
12
B
6
C
5
Lab Manual CSC159
Example 2. Multiply AX by 10h:
Mov
Mul
.
.
.
ax, var1
var2
var1
var2
; dx = 0002h , AX = 0000h
dw
dw
2000h
0010h
How to calculate:
AH
DH
AL
DL
2
000 2
0
0
0
1
0
0
0
0
0
2
0
0
0
2
0
0
0
0
0
0
0
0
6
Lab Manual CSC159
ii.
DIV
The DIV instructions perform both 8- and 16-bit division, signed and
unsigned. A single operand is supplied (register or memory operand),
which is assumed to be the divisor.
Syntax:
DIV
source
If the divisor is 8-bits long, AX is the dividend, AL the quotient, and AH
the remainder.
If the divisor is 16 bits, DX:AX is the dividend, AX the quotient, and DX
the remainder.
Dividend /
AX
DX:AX
Divisor
Operand
Operand
=
Quotient
AL
AX
Remainder
AH
DX
7
Lab Manual CSC159
Example 1.
8-bit division (83h/2 = 41h, remainder 1
mov
mov
div
ax , 0083h
bl , 2
bl
; dividend
; divisor
; AL = 41h,
AH = 01h
Example 1: 8 bit register data
Div CL
If AX register consist value of 005616 and the content of CL register is 1116, after this
instruction is executed, the content of register AH will be 0116,while the register AL
will have the quotient value of 0516
AX
00
56
AH
AL
CX
00
11
CH
CL
Div CL
AX
01
05
AH
How to calculate:
Example 2: 16 bit register data
AL
5
11 √0056
55
1
AL
AH
8
Lab Manual CSC159
Div CX
If AX register consist the value of 0F0516 ,the content of DX register is 068A16 and CX
register is 08E916, after these instructions are executed, the content of register AX
will have the quotient value of BBE116,while the register DX will have the remainder
value of 073C16.
AX
0F
05
AH
AL
DX
06
8A
DH
DL
CX
08
E9
CH
CL
Div CX
AX
BB
E1
AH
AL
DX
07
DH
3C
DL
9
Lab Manual CSC159
How to calculate:
1. Convert all values inside the registers to decimal
numbers.
CX=08E916 =(8 x 162) +(E x 161) +(9 x 160)
=(8 x 256) +(14 x 16) +(9 x 1)
=2048 + 224 +9
=228110
DX : AX=068A16 : 0F0516 =(6 x 166) +(8 x 165) +(A x 164)
+(F x 161) +(5x 160)
=(6 x 16777216) +(8 x 1048576)
+(10 x 65536)
+(15 x 256) +(5x 1)
=100663296 + 8388608
+655360 +3840+5
=10971110910
2. Do the quotient operation.
48097
2281 √109711109
9124
18471
AX
18248
22310
20529
17819
15967
1852
3. Convert from decimal to Hexadecimal.
16 | 48097
16 | 3006
16 | 187
|11
AX=BBE116
1
14
11
E
B
B
DX
10
Lab Manual CSC159
16 | 1852
16 | 115
|7
DX=073C16
12
3
7
C