A solution manual to
Assembly language
Programming
and the organization of
the IBM PC
Chapter 7
Logic, shift and rotate instructions
BY:- Ytha Yu & Charles Marut
prepared by :
Warda Aziz
Wardaaziz555@gmail.com

Question 1:
Perform the following logic operations:
A) 10101111 AND 10001011
B) 10110001 OR 01001001
C) 01111100 XOR 11011010
D) NOT 01011110
10101111 AND 10001011
10101111
AND10001011
10001011
10110001 OR 01001001
10110001
OR 01001001
11111001
01111100 XOR 11011010
01111100
XOR11011010
10100110
NOT 01011110
NOT 01011110
10100001
Question 2:
Give a logic instruction to do each of the following
A) Clear the even numbered bits of AX. Leaving the other bits unchanged
B) Set the MSB & LSB of BL, leaving other bits unchanged
C) Compliment the MSB of DX , leaving the other bits unchanged
D) Replace the value of the word variable WORD1 by its one’s compliment
Clear the even numbered bits of AX. Leaving the other bits unchanged
AND AX, 0AAAAh
;bits start from 0 not 1, so AAAA
Set the MSB & LSB of BL, leaving other bits unchanged
OR BL,81h
Compliment the MSB of DX , leaving the other bits unchanged
XOR DX,8000h
Replace the value of the word variable WORD1 by its one’s compliment
NOT WORD1
Question 3:
use the test instruction to do each of the following.
A. Set ZF if AX is zero
B. Clear ZF if BX contains an odd number
C. Set SF if DX contains a negative number
D. Set ZF if DX contains a zero or positive number
E. Set PF if BL contains an even number of 1 bits.
Solution :

;as we know TEST instruction deals with AND operation so,
Set ZF if AX is zero
TEST AX, FFFFh
Clear ZF if BX contains an odd number
TEST BX, 0001h
Set SF if DX contains a negative number
TEST DX, 8000h ;8=1000
Set ZF if DX contains a zero or positive number
TEST DX,8000H
Set PF if BL contains an even number of 1 bits.
TEST BL, FFh
Question 4:
Suppose AL contains 11001011b and CF=1. give the new contents of AL after each of
the following instruction is executed. Assume the preceding initial conditions for each
part of this question.
a. SHL AL,1
b. SHR AL,1
c. ROL AL,CL ; CL=2
d. ROR AL,CL ;CL=3
e. SAR AL,CL ;CL=2
f. RCL AL,1
g. RCR AL,CL ;CL=3
Question 5:
Write instructions to do each of the following. Assume that no overflow occurred.
a) Double the value of byte variable B5.
b) Multiply the value AL by 8.
c) Divide 32142 by 4 and put the quotient in AX.
d) Divide -2145 by 16 and put the quotient in BX.
Double the value of byte variable B5.
SHL B5,1
Multiply the value AL by 8.
Instruction Processing AL(before) AL(after) CF
SHL AL,1 10010110 11001011 10010110 1
SHR AL,1 01100101 11001011 01100101 1
ROL AL,CL ; CL=2 10010111
00101111
11001011 00101111 1
ROR AL,CL ;CL=3 11100101
11110010
01111001
11001011 01111001 0
SAR AL,CL ;CL=2 11100101
11110010
11001011 11110010 1
RCL AL,1 10010111 11001011 10010111 1
RCR AL,CL ;CL=3 11100101
11110010
11111001
11001011 11111001 0

MOV CL,3
SHL AL,CL
Divide 32142 by 4 and put the quotient in AX.
MOV AX, 32142
MOV CL,4
SHR AX,CL
Divide -2145 by 16 and put the quotient in BX.
MOV CL,4
MOV BX,-2145
SAR BX,CL
Question 6:
Write instructions to do each of the following:
a. Assuming AL has a value less than 10 , convert it to a decimal equivalent.
b. Assuming DL contains ASCII of upper case, convert it to lower case .
Assuming AL has a value less than 10 , convert it to a decimal equivalent.
MOV AH, 1
INT 21h
MOV AH,2
OR Al, 30h
MOV DL,AL
INT 21h
Assuming DL contains ASCII of upper case, convert it to lower case .
MOV AH, 1
INT 21h
MOV AH,2
OR Al, 20h
MOV DL,AL
INT 21h
Question 8:
Write a program that
 prompts the user to enter a character
 on subsequent lines prints its ASCII code in binary
 the number of 1 bits in its ASCII code
Solution:
.STACK 100h
.MODEL small
.DATA
m1 DB 'Type a character ','$'
m2 DB 0ah , 0dh, 'The ASCII code of '
c1 DB ?, 'in binary is:','$'
m3 DB 0ah, 0dh, 'The number of 1 bits is'
c2 DB ?, '$'
C3 DB ?
.CODE
MAIN PROC
;Data segment initialization
MOV AX, @DATA
MOV DS, AX

;displaying message M1
MOV AH,9
LEA DX,m1
INT 21h
;Taking character input
MOV AH,1
INT 21h
MOV C1,AL ;For ASCII conversion
MOV C3,AL ;For NO. OF 1 Bits
;ASCII conversion
MOV AH,9
LEA DX, M2
INT 21H
MOV AH,2
MOV CX,8
TOP:
SHL C1,1
JC set
MOV DL,'0'
INT 21H
JMP LABEL
SET:
MOV AH,2
MOV DL,'1'
INT 21H
JMP TOP
LABEL:
LOOP TOP
;Number of 1 bits
MOV AH,9
LEA DX,M3
INT 21H
MOV AL,0
MOV CX, 8
TOP1:
ROL C3,1
JNC NEXT
INC AL
NEXT:
LOOP TOP1
MOV AH,2
MOV DL,AL
ADD DL,30h
INT 21H
;dos exit
MOV ah,4Ch
INT 21h
main ENDP
END main
OUTPUT:

Question 9:
Write a program that prompts the user to enter a character and prints the ASCII code
of the character in hex on the next line. Repeat the process until the user types a carriage
return.
.stack 100h
.model small
.data
msg DB 0AH,0DH,'Enter a character $'
CHAR DB ?
output_msg DB 0Ah, 0Dh,'The ASCII of entered number is: $'
.code
main proc
;Data segment initialization
MOV AX, @DATA
MOV DS, AX
input_again:
;setting previous values to 0 otherwise previous values will reflect the result
MOV CHAR,0
MOV DH,0
MOV CL,0
MOV DL,0
MOV BX,0
MOV AH,9
LEA DX,msg
INT 21h
;input
MOV AH,1
INT 21H
;storing AL in char for displaying and in BX for output processing
MOV CHAR,AL
MOV BX, AL
;if entered char is 0 goto terminate2 else continue the program
CMP char, 0dh
JE terminate2
;OUTPUT
MOV AH,9
LEA DX, OUTPUT_MSG
INT 21H
;DH is used to output character upto four digits i.e., A=0041
MOV DH,4
hex_output:
;CL deals with 4 times rotation as 1 hex char is equal 4 digits i.e., 1=0001
MOV CL,4
MOV DL,BH

SHR DL,CL
;if shifted result is integer(0,1,2,...) then add 30h else if it is a character (A,B,C,...) add 37h
CMP DL,9
JG LETTER
ADD DL,30H ;integer
MOV AH,2
INT 21H
JMP LABEL
LETTER:
ADD DL,37H ;character
INT 21H
LABEL:
DEC DH
CMP DH,0
JE terminate
ROL BX, CL
JMP HEX_output
;Processing
terminate:
JMP input_again
TERMINATE2:
MOV ah,4ch
int 21h
main endp
end main
OUTPUT:
Question 10:
Write a program that prompts the user to type a hex number of four hex digits or less,
and outputs its binary on the next line. If the user enters an illegal character, he or she
should be prompted to begin again. Accept only uppercase letter.
.STACK 100h
.MODEL small
.DATA
prompt DB 0AH, 0DH,'ENTER THE HEX STRING $'
MSG DB 0AH, 0DH,"IN BINARY IT IS $"
MSG2 DB 0AH, 0DH,'INVALID INPUT$'
.CODE
main proc
;data segment initialization
MOV AX, @DATA
MOV DS, AX
input:
MOV BX,0

MOV CL,4
MOV AH,1
INT 21H
WHILE_:
;if carriage return go out of the loop
CMP AL,0DH
JE OUTPUT
;else compare if it is a hex or not i.e from 0 to 9 and A to F
;start of the loop
CMP AL,'0'
JL ERROR
CMP AL,'9'
JG LETTER
AND AL , 0FH
JMP SHIFT
LETTER:
CMP AL, 'F'
JG ERROR
CMP AL,'A'
JL ERROR
SUB AL, 37H
SHIFT:
SHL BX,CL
OR BL, AL
INT 21H
JMP WHILE_
;end of the input loop
;OUTPUT
;same trick used in question 8. shift the 16 bits and display the carry bit
output:
MOV AH,9
LEA DX, MSG
INT 21H
MOV AH,2
MOV CX,16
TOP:
SHL BX,1
JC set
MOV DL,'0'
INT 21H
JMP LABEL
SET:
MOV AH,2
MOV DL,'1'
INT 21H
LABEL:
LOOP TOP
JMP EXIT
ERROR:
MOV AH,9
LEA DX, MSG2
INT 21H

JMP INPUT
;END
EXIT:
MOV AH,4Ch
INT 21H
main endp
end main
OUTPUT:
Question 11:
Write a program that prompts the user to type a binary number of 16 digits or less
and outputs it in hex on the next line. If the user enters an illegal character he or she
should be prompted again.
.STACK 100h
.MODEL small
.DATA
prompt DB 0AH, 0DH,'ENTER THE BINARY STRING $'
MSG DB 0AH, 0DH,"IN HEX IT IS $"
MSG2 DB 0AH, 0DH,'INVALID INPUT ENTER THE STRING AGAIN $'
.CODE
main proc
;data segment initialization
MOV AX, @DATA
MOV DS, AX
MOV AH,9
LEA DX, PROMPT
INT 21H
input:
MOV CX,0
MOV BX,0
MOV AX,0
MOV BX,0
MOV AH,1
WHILE_:
INT 21H
CMP AL, '0'
JNE ERROR
CONTINUE:
MOV CX, 16
;if carriage return go out of the loop
SHIFT:
AND AL, 01H

SHL BX,1
OR BL,AL
LOOP WHILE_
ERROR:
CMP AL, '1'
JE CONTINUE
CMP AL,0DH
JE OUTPUT
MOV AH,9
LEA DX,MSG2
INT 21H
JMP INPUT
;OUTPUT
output:
MOV AH,9
LEA DX, MSG
INT 21H
MOV AH,2
MOV DH,4
hex_output:
;CL deals with 4 times rotation as 1 hex char is equal 4 digits i.e., 1=0001
MOV CL,4
MOV DL,BH
SHR DL,CL
;if shifted result is integer(0,1,2,...) then add 30h else if it is a character (A,B,C,...) add 37h
CMP DL,9
JG LETTER
ADD DL,30H ;integer
INT 21H
JMP LABEL
LETTER:
ADD DL,37H ;character
INT 21H
LABEL:
ROL BX, CL
DEC DH
CMP DH,0
JE EXIT
JMP HEX_output
EXIT:
MOV AH,4Ch
INT 21H
main endp
end main

OUTPUT:
Question 12:
Write a program that prompts the user to enter two binary numbers of up to 8 digits
each and prints their sum on the next line in binary . if the user enters an illegal character,
he or she should be prompted to begin again. Each input ends with a carriage return.
.STACK 100h
.MODEL small
.DATA
prompt DB 0AH, 0DH,'ENTER THE BINARY STRING $'
MSG2 DB 0AH, 0DH,'INVALID INPUT ENTER THE STRING AGAIN $'
CHAR1 DW ?
OUTPUT_MSG DB 0AH,0DH,'SUM OF THE BINARY STRINGS IS $'
.CODE
main proc
;data segment initialization
MOV AX, @DATA
MOV DS, AX
;Prompting user to enter the string
MOV AH,9
LEA DX, PROMPT
INT 21H
input:
;clearing the registers if invalid input is entered otherwise previous values will effect the result
MOV CX,0
MOV BX,0
MOV AX,0
MOV BX,0
MOV AH,1
WHILE_:
INT 21H
;in statement of comparing we are checking for :
;if entered input is equal to 0 or 1 then normal execution
;else if it is a carriage return ask for the second input
;else if it is other than 0,1,CR ask the user to enter again
CMP AL, '0'
JNE ERROR
CONTINUE:
MOV CX, 16
SHIFT:
AND AL, 01H
SHL BX,1
OR BL,AL
LOOP WHILE_

ERROR:
CMP AL, '1'
JE CONTINUE
CMP AL,0DH
JE INPUT2
MOV AH,9
LEA DX,MSG2
INT 21H
JMP INPUT
;2ND INPUT
;same as the first input
INPUT2:
MOV CHAR1,BX
MOV AH,9
LEA DX, PROMPT
INT 21H
input1:
MOV CX,0
MOV BX,0
MOV AX,0
MOV BX,0
MOV AH,1
WHILE_1:
INT 21H
CMP AL, '0'
JNE ERROR1
CONTINUE1:
MOV CX, 16
SHIFT1:
AND AL, 01H
SHL BX,1
OR BL,AL
LOOP WHILE_1
ERROR1:
CMP AL, '1'
JE CONTINUE1
CMP AL,0DH
JE OUTPUT
MOV AH,9
LEA DX,MSG2
INT 21H
JMP INPUT
;OUTPUT
OUTPUT:
MOV AH,9
LEA DX,OUTPUT_MSG
INT 21H

MOV CX,16
;we are adding the first and second strings and then shifting them left to get the binary
;this is same as question 8
;ans will store in BX convert it in binary
ADD BX,CHAR1
SHIFT_CONTINUE:
SHL BX,1
JC SET
MOV AH, 2
MOV DL,'0'
INT 21H
JMP LOOP_START
SET:MOV AH,2
MOV DL,'1'
INT 21H
LOOP_START:
LOOP SHIFT_CONTINUE
EXIT:
MOV AH,4Ch
INT 21H
main endp
end main
OUTPUT: