EXPT NO: DATE:

STRING MANIPULATION OPERATIONS IN 8086 MICROPROCESSOR

AIM: To write the assembly language program for performing the string manipulation operations in 8086 microprocessor

APPARATUS REQUIRED:

SL.NO

ITEM SPECIFICATION QUANTITY

1. Microprocessor kit 8086 12 Key board 13 Power Supply +5 V dc 1

ALGORITHM:

(i) COPING A STRING

1. Initialize the data segment .(DS)2. Initialize the extra data segment .(ES)3. Initialize the start of string in the DS. (SI)4. Initialize the start of string in the ES. (DI)5. Move the length of the string (FF) in CX register.6. Move the byte from DS TO ES, till CX=0.

(ii) SEARCHING A STRING

1. Initialize the extra segment .(ES)2. Initialize the start of string in the ES. (DI)3. Move the number of elements in the string in CX register. 4. Move the byte to be searched in the AL register.5. Scan for the byte in ES. If the byte is found ZF=0, move the address pointed

by ES:DIto BX.

(iii) FIND AND REPLACE

1. Initialize the extra segment .(E S)2. Initialize the start of string in the ES. (DI)3. Move the number of elements in the string in CX register. 4. Move the byte to be searched in the AL register.5. Store the ASCII code of the character that has to replace the scanned byte

in BL register.6. Scan for the byte in ES. If the byte is not found, ZF≠1 and repeat

scanning.7. If the byte is found, ZF=1.Move the content of BL register to ES:DI.

FLOWCHART

COPING A STRING

START

Initialize DS, ES, SI, DI

CX=length of string, DF=0.

Move a byte from source string (DS) to destination string (ES)

Decrement CX

Check for

ZF=1 NO

YES

STOP

SEARCHING A STRING

START

Initialize DS, ES, SI, DI

CX=length of the string, DF=0.

Scan for a particular character specified in AL Register.

NO Check for

ZF=1

YES

Move DI to BX

STOP

¿

FIND AND REPLACE

START

Initialize DS, ES, SI, DI

CX=length of the string in ES,DF=0.

Scan for a particular character specified in AL

Check NO for ZF=1

YES

Move the content ofBL to ES: DI

STOP

PROGRAM

COPYING A STRINGADDRESS OPCODE LABEL PROGRAM COMMENTS

MOV SI,1200H Initialize destination address

MOV DI,1300H Initialize starting address

MOV CX,0006H Initialize array size

CLD Clear direction flag

REP MOVSB Copy the contents of source intodestination until count reaches zero

INT 3 Stop

SEARCHING FOR A CHARACTER IN THE STRINGADDRESS OPCODE LABEL PROGRAM COMMENTS

MOV DI,1300H Initialize destination address

MOV SI, 1400H Initialize starting address

MOV CX, 0006H Initialize array size

MOV BL,00H Initialize the relative address

CLD Clear direction flag

MOV AL, 08H Store the string to be searched

LOOP2: NOP Delay

SCASB Scan until the string is found

JNZ LOOP1 Jump if the string is found

MOV [SI],BL Move the relative address to SI.

INC SI Increment the memory pointer

LOOP1: INC BL Increment the relative address

LOOP LOOP2 Repeat until the count reaches zero

INT 3 Stop

FIND AND REPLACE A CHARACTER IN THE STRINGADDRESS OPCODE LABEL PROGRAM COMMENTS

MOV DI,1300H Initialize starting address

MOV CX, 0006H Initialize array size

CLD Clear direction flag

MOV AL, 08H Store the string to be searched

MOV BH,30H Store the string to be replaced

BACK:SCASB Scan until the string is found

JNZ LOOP1 Is the string found

DEC DI Decrement the destination address

MOV [DI],BL Replace the string

LOOP1: LOOP BACK Continue until count zero.

INT 3 Stop

OUTPUT

COPYING A STRING

INPUT

MEMORYDATA

OUTPUT

MEMORY

DATA

SEARCHING FOR A CHARACTER IN THE STRING

INPUTMEMORYDATA

OUTPUTMEMORY LOCATIONDATA

FIND AND REPLACE A CHARACTER IN THE STRING

INPUTMEMORY

DATA

OUTPUT

MEMORY

DATA

RESULT