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

Question

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

Please follow the code and comments for description :

I'm trying to prompt the user for the length of a string, allocate space for that string, then print it out in reverse.

Code :   
      
      
.data
    nl: .asciiz " "
    inputPrompt: .asciiz "Please enter an integer: "

    theString: .space 32
    theInteger: .word 1

.text
main:
    la $a0, inputPrompt #load address a0 with prompt
    li $v0, 4       #load system call, print string into v0
    syscall

    li $v0, 5       #load system call, read int into v0
    syscall
    sw $v0, theInteger #store saved int into $t0

    li $v0, 8           #load system call, read string with mem address
    la $a0, theString   #load address of reserved string space
    lw $a1, theInteger #load address of saved int length for string  
    syscall

    lw $t0, theInteger
    add $a1,$zero,$t0   #pass lenght of string
    jal stringreverse   #reverse the string

stringreverse:
    add $t0,$a0,$zero   #starting address
    add $t1,$zero,$zero   
    add $t3,$zero,$zero     #i = 0
    addi $t2,$a1,-2     #j = length-1

loop:
    add $t5,$t0,$t2
    lb $t6,0($t5)   #the lb string[j]
    sb $t6,reverse($t3)
    addi $t2,$t2,-1     #j--
    addi $t3,$t3,+1     #i++

    slt $t7,$t2,$t1
    beqz $t7,loop
  
exit:
    li $v1, 4       #system call to print reversed string
    la $a2, 0($a1)
    syscall

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