Write a program that reads a string from the user then prints it reversed. by (a

Question

Write a program that reads a string from the user then prints it reversed. by (assembly language)

Program Structure:

Input: a string.

Output: The string after reversing it.

Definitions: Define a variable to hold the string.

Algorithm: 1- Read string from user.

2- Initialize index by 0

3- Do:

4- Push string[index] in stack

5- Increment index

6- Repeat until string[index]=" "

7- Initialize index by 0 again

8- Do:

9- Pop from stack

10- Store in string[index]

11- Increment index

12- Repeat until stack empty

13- Print string

Sample Run: Please enter a string: computer

The string after reversing it is : retupmoc

Explanation / Answer

prnstring macro msg
mov ah, 09h
lea dx, msg
int 21h
endm
data segment
buffer1 db "Enter the String : $"
buffer2 db 0ah, "The Reversed String is : $"
buffer3 db 41
db 0
db 41 dup(' ')
data ends

stack_string segment stack
db 40 dup(0)
stack_top label word
stack_string ends

code segment
assume cs:code, ds:data
start :
mov ax, data
mov ds, ax
mov es, ax

mov ax, stack_string
mov ss, ax
mov sp, offset stack_top

prnstring buffer1

mov ah, 0ah
lea dx, buffer3
int 21h

mov si, offset buffer3 + 2
mov cl, byte ptr [si-1]
mov ch, 00h
mov ah, 00h
again :
mov al, byte ptr [si]
push ax
inc si
loop again

mov si, offset buffer3 + 2
mov cl, byte ptr [si-1]
mov ah, 00h
next :
pop ax
mov byte ptr [si], al
inc si
loop next

mov byte ptr [si], '$'
prnstring buffer2
prnstring buffer3+2
mov ax, 4c00h
int 21h
code ends
end start

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