9.STRING COMPARISION

8/7/2019 9.STRING COMPARISION

1/7

STRING COMPARISION

Aim:

To write an ALP to compare two strings and display whether two strings are

equal or different

Apparatus:

y MASM softwarey Personal computer

Register sused: AX,CX,DX,DS,ES,SI,DI

Portsused: None

Problemanalysis:

Let us assume that string1 and string2 are available in the data

segment area. Similarly the prompt1 and prompt2 are also available in data

segment area. These prompts are useful to display the message after processing

whether the strings are same or different.

In the comparison, one character at a time from string1 is read

and compared with string2.The operation has to be repeated till all the characters

are compared. Counter may be used to check whether all the characters are

compared. After comparison, if both the strings are same then invoke routine to

display the message available in prompt1.Otherwise display the message availble

in prompt2.Even if the one character is different immediately display the message

available in prompt2.


2/7

Flow chart:

NO

yes

START

Initialize the data and extra segmet registers

Load offset address of string1 in SI and string2 In DI

clear the direction flag

Intialize the counter with no. of characters

Load the offset address of prompt2 and display

the message available in prompt2

Invoke the interrupt routine to come to DOS

prompt

STOP

Load the offset address

of prompt1 & display th

message available at

prompt1

Is

Str1!=str2


3/7

Algorithm:

1. Start2. Initialize the data and extra segment registers3. Load the offset address of string1 and string24. Clear the direction flag5. Initialize the counter with number of characters6. Compare the string and repeat,if the string is not equal goto step 87. If the string is same,load the offset address of prompt1 and display

the message available in prompt

8. Load the offset address of prompt2 and display the messageavailable in prompt

9. Invoke the interrupt routine to come to DOS prompt10.End of the program

Program:

ASSUME CS:code,DS:data,ES:data

Data segment

Str1 DB 0AH,ODH,BHARAT ISMAHAN HAI,0AH,0DH,$

Str2 DB 0AH,ODH,BHARAT ISMAHAN HAI,0AH,0DH,$

Prompt1 DB 0AH,ODH,THE STRINGS ARE EQUAL,0AH,0DH,$

Prompt2 DB 0AH,ODH,THE STRINGS ARE EQUAL,0AH,0DH,$

Data ends


4/7

Code segment

Start:Mov ax,data

Mov ds,ax

Mov es,ax

Mov ss,ax

Mov cx,0015h

CLD

Repeat:CMPS str1,str

JNE mismatch

LEA dx,prompt1

Mov ah,09h

INT 21h

JMP over

Mismatch:LEA dx,prompt2

Mov ah,09h

INT 21h

Over: mov ah,4ch

INT 21h

Code ends

End start.


5/7

Procedure:

Preparing an assembly language program for execution:

1)with the help of an editor,TYPE the program,with an extension.asm

Ex: pragati.asm

2) use an assembler (ex:MASM.exe)to create.obj file, without any error

If any error occur during the assembly , then use the editor to re-edit the user

program and correct the syntax errors and other specified errors.

Once there is no error in the assembly language program , the OBJ file is created

after assembly.

3) use the linker to create a.EXE file from the OBJ file. If there is no error in linking,

then go to next step. if there is any error go back to the step 1and make necessary

corrections in the .ASM

File and then follow the step 2&3

4)Execute the created EXE file, check the output. If the expected result is

obtained, then it means the logic of the program is correct

If the expected result is not obtained , then make use of DEBUG routine to check

the logic of the user program may be using G command

Codetable:

Effective

address

Hex code Mnemonics Operands Comments

0000 B8430B MOV AX,0B43 Store data into ax


6/7

register

0003 8ED8 MOV DS,AX Store AX value into D

register

0005 8EC0 MOV ES,AX Store AX value into E

register0007 B92000 MOV CX,0020 Store 0020 into CX

register

000A FC CLD Clear direction flag

000B 8D360000 LEA SI,[0000] Load the effective

address of str1 into S

register

000F 8D3E1500 LEA DI,[0015] Load the effective

address of str2 into D

register0013 F3 REPZ Repeat process until

count is zero

0014 A6 CMPSB Compare str1 with st

0015 750A JNZ 0021 Jump if not zero

0017 BA2900 MOV DX,0029 Set offset address of

prompt1 to DX regist

001A B409 MOV AH,09 Display prompt1 mes

001C CD21 INT 21 Interrupt

001E EB08 JMP 0028 Jump to over

0021 BA3A00 MOV DX,003A Store offset address o

prompt2

0024 B409 MOV AH,09 Display prompt2 mes

0026 CD21 INT 21 Interrupt

0028 B44C MOV AH,4C Move to DOS prompt

002A CD21 INT 21 Interrupt

Result:

Input: BHARAT ISMAHAN HAI

BHARAT ISMAHAN HAI


7/7

Output: the given strings are equal

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9.STRING COMPARISION