Answer:

        .text
        .globl  main
main:  
        # input the string

        # push each character onto the stack

        # pop chars from stack back into the buffer

        # print the reversed string

        .data
str:    .space  128     # character buffer

First Section

The first section of the program reads a line from the terminal in the usual way. To shorten the program, there is no user prompt.

Next, the stack is initialized. Null is pushed onto the stack. Later on, the stack will be popped until this null is encountered.

# Reverse and output a user-supplied string
#
# Settings: Load delays OFF; Branch delays OFF,
#           Trap file    ON; Pseudoinstructions ON   
#
# $t0 --- character pushed or popped
# $t1 --- index into string buffer str

        .text
        .globl  main

main:   #input the string
        li      $v0,8          # service code
        la      $a0,str        # address of buffer
        li      $a1,128        # buffer length 
        syscall       
                               # initialize the stack:        
        li      $t0,      # push a null
         
             $sp,$sp,4    # onto the stack
        
        sw      $t0,( )   # to signal its bottom
        li      $t1,0          # index of first char in str buffer

        # push each character onto the stack

        # pop chars from stack back into the buffer

        # print the reversed string

        .data
str:    .space  128            # character buffer

Answer:

First Section

QUESTION 12: