cw_1.asm

.data
    buffer_for_input_string: .space 100
    buffer_for_processed_string: .space 100
    prompt_for_input: .asciiz "Please enter your string:\n"
    prompt_for_output: .asciiz "Your processed string is as follows:\n"

.text
    main:
    # prompting the user with a message for a string input:
    li $v0, 4
    la $a0, prompt_for_input
    syscall

    # reading the input string and putting it in the memory:
    # the starting address of the string is accessible as buffer_for_input_string
    # 100 is the hard-coded maximum length of the null-terminated string that is
    # going to be read from the input. So effectively, up to 99 ascii characters.
    li $v0, 8
    la $a0, buffer_for_input_string
    li $a1, 100
    syscall

    # >>>> MAKE YOUR CHANGES BELOW HERE:

    # Looping over characters of the string:
    la      $t0, buffer_for_input_string
    la      $t1, buffer_for_processed_string
    
    Loop:
    lb      $t2, 0($t0) 
    beq     $t2, ',', PUNC
    beq     $t2, '.', PUNC
    beq     $t2, '?', PUNC 
    beq     $t2, ';', PUNC
    beq     $t2, ':', PUNC
    beq     $t2, '!', PUNC
    j CONTINUE

    PUNC:
    addi, $t0, $t0, 1
    lb $t2, 0($t0)

    # potentially do some processing on the character loaded in t2
    CONTINUE:
    sb      $t2, 0($t1)
    addi    $t0, $t0, 1
    addi    $t1, $t1, 1
    bne     $t2, $zero, Loop # keep going until you reach the end of the string,
                            # which is demarcated by the null character.

    # <<<< MAKE YOUR CHANGES ABOVE HERE

    # prompting the user with a message for the processed output:
    li $v0, 4
    la $a0, prompt_for_output
    syscall

    # printing the processed output
    # note that v0 already holds 4, the syscall code for printing a string.
    la $a0, buffer_for_processed_string
    syscall

    # Finish the programme:
    li $v0, 10      # syscall code for exit
    syscall         # exit