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Friday, February 21, 2014
ASSUME DS: DATA, CS: CODE
MSG1 DB 0AH, 0DH, "ENTER THE FIRST STRING : ","$"
MSG2 DB 0AH, 0DH, "ENTER THE SECOND STRING : ","$"
MSG3 DB 0AH, 0DH, "STRINGS ARE SAME","$"
MSG4 DB 0AH, 0DH, "STRINGS ARE NOT SAME","$"
MSG5 DB 0AH, 0DH, "LENGTH OF FIRST STRING IS: ","$"
MSG6 DB 0AH, 0DH, "LENGTH OF SECOND
STRING IS: ","$"
STR1 DB 100 DUP(' '),"$" ;reserve 100 bytes of blank memory
location for STR1 array
STR2 DB 100 DUP(' '),"$" ;reserve 100 bytes of blank memory
location for STR2 array
LEN1 DB ? ; variable to store the length of 1st
string.
LEN2 DB ? ; variable to store the length of 2nd string.
DATA ENDS
DISPLAY
MACRO MSG ;DISPLAY macro definition starts
here, this macro is used to display
MOV DX, OFFSET MSG ; message, whose
offset address is stored in DX using 09h
MOV AH, 09H ; with 21H DOS
interrupt.
INT 21H
ENDM ; end of macro
definition
DISP
MACRO NUM ;DISP macro definition starts here, this macro
is used to display the length
MOV DL, NUM ; of the string ( character display) using
02H. with DOS 21H interrupt.
MOV AH, 02H
INT 21H
ENDM ; end of macro definition.
CODE SEGMENT ; code
segment starts
START: MOV AX, DATA
MOV DS, AX ; initializing
data segment
MOV
ES, AX
;
initializing extra segment
DISPLAY MSG1 ; invoke DISPLAY
macro to display MSG1
MOV SI, OFFSET STR1 ; SI points to the 1st memory
location of STR1 array
CALL READ
; call READ procedure
to read the 1st string from
keyboard
MOV
LEN1,
BL ;
store
the length of the 1st string in LEN1 variable
DISPLAY MSG2 ; invoke DISPLAY
macro to display MSG2
MOV SI, OFFSET STR2 ; SI points to
the 1st memory location of STR2 array
CALL READ ; call procedure READ to read the1st string from
keyboard
MOV
LEN2,
BL ; store
the length of the 2nd string in LEN2 variable.
MOV
AL, LEN1
CMP
AL, LEN2 ; compare the length of these two strings.
JNE NOTEQUAL ; if not equal go
to label NOTEQUAL
MOV SI, OFFSET STR1 ; SI points to 1st character
of STR1 array (source string)
MOV
DI, OFFSET STR2 ; DI points to 1st character of
STR2 array (destination string).
MOV CL, LEN1 ; store the length of the string in CL ( either
string1 or string2)
CLD ; clear the
direction flag for auto increment mode
REPE CMPSB ; compare the string bytes pointed by SI
and DI
JNE NOTEQUAL ; if strings are
not equal jump to label NOTEQUAL
DISPLAY MSG3 ; otherwise invoke display macro to
display MSG3 (strings are same)
JMP
NEXT ; jump to label
NEXT, to display the length.
NOTEQUAL: DISPLAY
MSG4 ; invoke display macro to display
MSG4 (strings are not same)
NEXT : DISPLAY MSG5
; invoke display macro to display
MSG5.
MOV
AL, LEN1 ; store the
length of 1st string in AL
CALL DISP_LEN
; Call DISP_LEN
procedure to display the length of 1st string.
DISPLAY MSG6 ; invoke
display macro to display MSG6.
MOV
AL, LEN2 ; store the
length of 2nd string in AL.
CALL
DISP_LEN ; Call DISP_LEN
procedure to display the length of 2nd string.
MOV AH,4CH ; terminate the program.
INT
21H
READ PROC NEAR ; start of READ procedure (procedure
defined in the same segment)
MOV BL, 00 ; initially
BL = 00, used as counter to store the number of
characters .
BACK: MOV AH, 01H
INT 21H ; read a character from keyboard, 01h with 21H dos interrupt
CMP AL, 0DH ;
compare with enter key.
JE STOP ; if equal terminate the read process
INC BL ; after reading a character from
keyboard, increment BL by 1
MOV [SI], AL ; store the character in array pointed by SI
INC SI ; increment SI by 1 to point to the
next location of array.
JMP BACK ; jump to BACK to read the next
character
STOP: RET ; return to main
READ ENDP ; end of READ procedure
DISP_LEN PROC NEAR ; start of DISP_LEN procedure
AAM ;convert the 2 digit binary (hex) length in AL
to unpacked BCD
ADD AX, 3030H ;add
AX with 3030H to get the ASCII value of that 2 digit no.
PUSH AX ; store the AX content temporarily in
Stack memory.
DISP AH ; invoke DISP macro to display the
upper digit of the length.
POP AX ; retrieve AX content from stack
DISP AL ; invoke DISP macro to display the lower
digit of the length
RET ;
return to main.
DISP_LEN ENDP ; end of DISP_LEN procedure
CODE ENDS ; end
of code segment
END START ; end of program.
Output:
D:\MASM>
Masm 6a.asm;
D:\MASM>
Link 6a.obj;
D:\MASM>
6a.exe
D:\MASM>
6a.exe
Or
D:\MASM>
TD 6a.exe
Then press F7 to trace the program (line by line execution)
ASSUME DS:DATA, CS:CODE
DATA SEGMENT ; start of data
segment
STR DB 25 DUP(' '),'$' ; reserve 25
bytes blank memory location for STR array(to store
;user entered
string)
RSTR DB 25 DUP(' '),'$' ; reserve 25
bytes blank memory location for RSTR array( to
;store the
reversed string)
COUNT DB ? ; a variable is declared to store the total no.
characters present in
;user
entered string.
MSG1 DB 0DH, 0AH, 'ENTER A STRING :', '$'
MSG2 DB 0DH, 0AH, 'REVERSE OF THE STRING IS
:', '$'
MSG3 DB 0DH, 0AH, 'ENTERED STRING IS PALINDROME', '$'
MSG4 DB 0DH, 0AH, 'ENTERED STRING IS NOT PALINDROME', '$'
DATA ENDS ; end
of data segment
DISPLAY
MACRO MSG ; DISPLAY macro
definition starts here ( used to display the
;various messages
on the screen)
MOV
DX, OFFSET MSG
MOV AH, 09H ; use service no.
09H to display the message on the screen
INT 21H ; using DOS
interrupt 21H
ENDM
CODE SEGMENT ; end of code
segment
START :
MOV AX, DATA
MOV DS,
AX ; initializing data segment.
MOV ES,
AX ; initializing
extra segment.
XOR CX, CX ; clear
CX register content
MOV SI, OFFSET
STR
; STR array’s 1st
memory location is pointed by SI (offset
addr)
DISPLAY
MSG1 ;
macro is invoked to display the 1st message MSG1
BACK: MOV AH, 01H ; using 01H service no with DOS interrupt
21H, read
INT 21H ; a character from keyboard.
CMP AL, 0DH ;compare
the user entered character with the enter
key (ascii)
JE STOP ; if it is equal to enter key, then go to STOP,
& terminate the read process.
MOV [SI], AL ; otherwise store the character in STR
array
INC SI ; after copying a character to the STR
array, memory pointer is
; incremented by
1, to point to the next memory location.
INC CL ; after
reading a character, counter value in CL is incremented by 1
; to indicate the length of the
string.
JMP BACK ; go to BACK and
read the next character from keyboard.
STOP: MOV COUNT, CL ; store the
length of the input string in COUNT variable.
DEC SI
; SI points to the last character of the input string in
STR array.
MOV DI, OFFSET
RSTR ; DI points to the
1st location of RSTR array (store the reversed string)
AGAIN: MOV AL, [SI]
MOV [DI], AL ; generates
the reverse of STR array contents and stores in RSTR
INC DI ; DI points the next position in RSTR
array.
DEC SI ; SI points to the previous character in
STR array.
LOOP AGAIN ; if count (length) in CL is not zero, then jump
to AGAIN
DISPLAY MSG2 ; macro is
invoked to display the message MSG2
DISPLAY
RSTR ;
invoke the macro to
print the reversed string, which is in RSTR
MOV CL, COUNT ;
length is again moved to CL
MOV
SI, OFFSET STR
; SI points to
the 1st character of the string in STR
MOV
DI, OFFSET RSTR ; DI points to
the 1st character of the reversed string in RSTR
CLD ;clear direction flag for auto increment
mode
REPE CMPSB ; compare the
string bytes pointed by SI and DI
JNE NEXT ; if strings are not equal jump to label
NEXT
DISPLAY MSG3 ; otherwise invoke
the macro to display the message MSG3
JMP
EXIT ; jump to label
EXIT to terminate the program
NEXT:
DISPLAY MSG4 ;
invoke the macro to display the message MSG4
EXIT: MOV AH, 4CH ; terminate the
program
INT 21H
CODE ENDS ; end of code
segment.
END
START ; end of program
Output:
D:\MASM>
Masm 5a.asm;
D:\MASM>
Link 5a.obj;
D:\MASM>
5a.exe
D:\MASM>
5a.exe
OR
D:\MASM>
TD 5a.exe
Then press F7 to trace the program (line by line execution).
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