Write a MIPS program that declares a string (with .asciiz) containing a fairly s

Question

Write a MIPS program that declares a string (with .asciiz) containing a fairly short string, such as "The quick brown fox jumps over a lazy dog".    .data str: .asciiz "The quick brown fox jumps over a lazy dog"

The program will reverse the string in place; that is, without copying it to another place in RAM. The basic algorithm is as follows:

Create 2 pointers, here called s and t (use registers)

Set pointer s to the start of the string.

Set pointer t to the end of the string  

(scan for the '' terminator, then back up one place).

while( s < t )   

   swap *s and *t (here, * means "thing pointed to by" s and t)   

   increment s   

   decrement t end loop

A swap routine in a language like C needs a temporary location c, e.g.:

c = *t

*t = *s

*s = c

In C, *s means the thing pointed to by s. In assembler the registers you lb the bytes into can serve as the temporary location(s), so you don't need another location to hold a temporary value.

Explanation / Answer

Given below is the code for the question with output . Please don't forget to rate the answer if it helped. Thank you.

.data
str: .asciiz "The quick brown fox jumps over a lazy dog"
beforeMsg: .asciiz "The string before reverse is : "
afterMsg: .asciiz " The string after reverse is : "

.text

#display the string before reversing
li $v0, 4
la $a0, beforeMsg
syscall

li $v0, 4
la $a0, str
syscall

#=================
la $t0, str # t0 intially pointing to beginning of the string
la $t1, str #poiner to end of string, initially pointing to beginning

#make the end pointer reach the end of string

find_end:
lb $t2, ($t1) #get the char pointed by end pointer
beq $t2, '', found_end #if its end of string , then end pointer is indeed reached end
addi $t1, $t1, 1
b find_end

found_end:
#come back 1 location since its pointing to null terminator
sub $t1, $t1, 1

loop:
bge $t0, $t1, end_loop #if the begininng poiter is >= end pointer , we can stop
lb $t2, ($t0) #store beginning char in t2
lb $t3, ($t1) #store end char in $t3

#store the chars in exchanged positions
sb $t2, ($t1)
sb $t3, ($t0)
addi $t0, $t0, 1 #increment front pointer
sub $t1, $t1, 1 #decremetn back pointer
b loop

end_loop:
#display the string after reversing
li $v0, 4
la $a0, afterMsg
syscall

li $v0, 4
la $a0, str
syscall

#exit
li $v0, 10
syscall

outptu

The string before reverse is : The quick brown fox jumps over a lazy dog
The string after reverse is : god yzal a revo spmuj xof nworb kciuq ehT

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