Menu driven program for string operations(Accept String,Display String,Length,Reverse, Palindrome ) in TASM
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Objective:
Write a
menu driven assembly language program to
accept ,display the string, find the length of string, reverse the string,
check the string is palindrome or not and scan the string to check whether a
accepted letter is present or not
Prerequisite:
TASM
assembler
Description:
There
are several string instructions, used to move large blocks of data or stings
and perform operations on strings.
·
Memory
string source - DS:SI
·
Memory
string destination - ES:DI
·
String
can be processed in forward and reverse direction.
·
If
DF=1 auto decrement for SI and DI
·
If
DF=0 auto increment for SI and DI
Algorithm:
1.
Start
2.
Initialize
data segment through AX register in the DS register.
3.
If
choice =1 then goto step no.4 (accept the string)else goto the step no.14
4.
Display
the message “Enter the string”
5.
Initialize
the SI with 1000h(source index)
6.
Initialize
the DI with 2000h(destination index)
7.
Accept
the character through keyboard(AL=52h
i.e ASCII hex value of ‘m’)
8.
Move
the AL contents to a location pointed by SI and DI.
9.
Increment
the CL register contents by 1
10. Increment SI and DI by 1
11. Repeat the step 7 to 10 till
Enter key get pressed(i.e AL=0Dh ASCII hex value for enter key used to detect
the end of the string.)
12. Decrement the CL by 1 ( to avoid
the enter key as a part of the string to obtain correct length value)
13. Preserve the length in temporary
variable say count from CL
14. If choice = 2 then goto step
no.15 (display the string)else goto step no. 21
15. Initialize SI again with 1000h
(string source)
16. Move the content of location
pointed by SI to DL
17. Display the character on the
screen
18. Increment SI by 1and decrement
the CL by 1
19. Repeat the step from 15 to 18
till Zero flag will come set (i.e CL reaches to zero).
20. Load the String length from count
to CL register back.
21. If choice=3 (display the length of string) then
goto step no. 22 else goto step no. 24
22. Move the contents of CL to AL and
add 30h to AL
23. Move the AL contents to DL and display
the length of string.
24. If choice=4 (Reverse the string) then
goto step no. 24 else goto step no.30
25. Add CX (e.g CX=0005)to SI to make
SI to point to the last letter of String.
26. Decrement to SI by 1 as SI will
start from 0 index (e.x 1000 to 10004 are the locations if string is of 5
letters)
27. Move the letter pointed by SI to
DL and display it on the screen
28. Decrement the SI by 1 and
decrement the CL by 1
29. Repeat step 25 to 29 till CL
reaches to zero if zero flag get set.
30. If choice = 5 then goto step no.
31 else goto the step no.43
31. Initialize SI with 1000h again
32. Initialize DI with 2000h again
33. Load CL with original length of
string from count
34. Add DI with CX (e.x CX=0005)so DI
will point to the last letter of string
35. Move the letter from location
pointed by SI to AL
36. Move the letter from location
pointed by DI to BL
37. Compare the AL and BL if zero
flag is not set then goto step no. 38 else goto step no 39
38. Display the string is not
palindrome.
39. Increment the SI by 1 and
Decrement DI by 1
40. Decrement CL by 1.
41. Repeat step no. 34 to 38 till CL
reaches to zero
42. If zero flag is set then display
the string is palindrome.
43. If choice=6 then goto step no. 44
else goto step no 49
44. Accept the letter to be searched
in AL.
45. Load CL with original length of
string from count
46. Initialize the DI with 2000h
47. Use REPNE SCASB instruction this
instruction scans the string for a letter stops when it finds the first
occurrence of a letter. It decrements CX also by 1 for every scan. When this
instruction stops CX will contain value as position-1 value.
48. Obtain the position of a letter by subtracting
total length-CX value and display it on the screen.
49. Stop.
TASM Program :Data Segment
chc db 0dh,0ah,"Choose Operation: $"
chc1 db 0dh,0ah," 1. Accept String $"
chc2 db 0dh,0ah," 2. Display String $"
chc3 db 0dh,0ah," 3. Display Length $"
chc4 db 0dh,0ah," 4. Display Reverse $"
chc5 db 0dh,0ah," 5. Check Palindrome $"
chc6 db 0dh,0ah," 6. Exit $"
len db ?
msg db 0dh,0ah,"Please enter the String: $"
msg1 db 0dh,0ah,"The length of the entered String is: $"
msg2 db 0dh,0ah,"The entered String is: $"
msg3 db 0dh,0ah,"The reverse of the entered String is: $"
pal db 0dh,0ah,"The String is a Palindrome. $"
npal db 0dh,0ah,"The String is not a Palindrome. $"
newl db 0dh,0ah," $"
Data ends
Code Segment
assume DS:Data,CS:Code
Start:
mov ax,Data
mov DS,ax
call AcceptString
l: mov dx,offset chc
mov ah,09h
int 21h
mov dx,offset chc1
mov ah,09h
int 21h
mov dx,offset chc2
mov ah,09h
int 21h
mov dx,offset chc3
mov ah,09h
int 21h
mov dx,offset chc4
mov ah,09h
int 21h
mov dx,offset chc5
mov ah,09h
int 21h
mov dx,offset chc6
mov ah,09h
int 21h
mov dx,offset newl
mov ah,09h
int 21h
mov ah,01h
int 21h
sub al,30h
cmp al,06h
jz ex
cmp al,05h
jne n1
call CheckPal
n1: cmp al,04h
jne n2
call DisplayRev
n2: cmp al,03h
jne n3
call DisplayLength
n3: cmp al,02h
jne n4
call DisplayString
n4: cmp al,01h
jne l
call AcceptString
jmp l
ex: mov ah,4ch
int 21h
AcceptString proc
mov si,1000h
mov di,1000h
mov cx,0000h
mov dx,offset msg
mov ah,09h
int 21h
back:
mov ah,01h
int 21h
cmp al,0dh
je comp
inc cx
mov [si],al
mov [di],al
inc si
inc di
jmp back
comp: mov len,cl
ret
endp
DisplayString proc
mov dx,offset msg2
mov ah,09h
int 21h
mov cl,len
mov ch,00h
mov si,1000h
disp:
mov dl,[si]
mov ah,02h
int 21h
inc si
loop disp
ret
endp
DisplayLength proc
mov dx,offset msg1
mov ah,09h
int 21h
mov bl,len
call DispNum
ret
endp
DispNum proc
mov al,bl
and al,0f0h
ror al,4
mov dl,al
call HexDisp
mov ah,02h
int 21h
mov al,bl
and al,0fh
mov dl,al
call HexDisp
mov ah,02h
int 21h
endp
HexDisp proc
cmp dl,0ah
jc nothex
add dl,07h
nothex: add dl,30h
ret
endp
DisplayRev proc
mov dx,offset msg3
mov ah,09h
int 21h
mov cl,len
mov ch,00h
mov si,1000h
add si,cx
dec si
dispr:
mov dl,[si]
mov ah,02h
int 21h
dec si
loop dispr
ret
endp
CheckPal proc
mov al,len
mov ah,00h
mov bl,02h
div bl
mov cl,len
dec cl
mov ch,00h
mov di,1000h
mov si,1000h
add di,cx
mov cl,al
mov ch,00h
pchk:
mov al,[si]
cmp al,[di]
jnz np
inc si
dec di
loop pchk
mov dx,offset pal
mov ah,09h
int 21h
ret
np:
mov dx,offset npal
mov ah,09h
int 21h
ret
endp
Code ends
end StartC:\TASM\BIN>tasm string.asm Turbo Assembler Version 4.1 Copyright (c) 1988, 1996 Borland International Assembling file: string.asm Error messages: None Warning messages: None Passes: 1 Remaining memory: 453k C:\TASM\BIN>tlink string.obj Turbo Link Version 7.1.30.1. Copyright (c) 1987, 1996 Borland International Warning: No stack C:\TASM\BIN>string Please enter the String: Micro Processors Choose Operation: 1. Accept String 2. Display String 3. Display Length 4. Display Reverse 5. Check Palindrome 6. Exit 2 The entered String is: Micro Processors Choose Operation: 1. Accept String 2. Display String 3. Display Length 4. Display Reverse 5. Check Palindrome 6. Exit 3 The length of the entered String is: 10 Choose Operation: 1. Accept String 2. Display String 3. Display Length 4. Display Reverse 5. Check Palindrome 6. Exit 4 The reverse of the entered String is: srossecorP orciM Choose Operation: 1. Accept String 2. Display String 3. Display Length 4. Display Reverse 5. Check Palindrome 6. Exit 5 The String is not a Palindrome. Choose Operation: 1. Accept String 2. Display String 3. Display Length 4. Display Reverse 5. Check Palindrome 6. Exit 1 Please enter the String: abcba Choose Operation: 1. Accept String 2. Display String 3. Display Length 4. Display Reverse 5. Check Palindrome 6. Exit 5 The String is a Palindrome. Choose Operation: 1. Accept String 2. Display String 3. Display Length 4. Display Reverse 5. Check Palindrome 6. Exit 6 --------------------------------
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