.data
str:
        .asciiz "Per"
        .asciiz "Per aspera, ad astra!"
        .asciiz "12"
msg:
        .asciiz "The length of string \n   \"%/a1/s\"\nis %/v1/d.\n"

        .text
        .globl __start
__start:
        la $a0, str             # Load address of string.
        jal strlen              # Call strlen procedure.
        nop
        la $a1, str             # Load address of string to $a1
        addi $v1, $v0, 0        # Move length of string to $v1
        addi $v0, $0, 11        # System call code for message.
        la $a0, msg             # Address of message.
        syscall
        addi $v0, $0, 10        # System call code for exit.
        syscall

strlen:
        ## Register Usage
        #
        # $a0: Address of first character of string.
        # $v0: Return value, the length of the string.
        #


        addi $v0, $a0, 1
        
LOOP:
        lbu $t0, 0($a0)         # Load next character in string into $t0
        bne $t0, $0, LOOP       # If it's not zero, continue
        addi $a0, $a0, 1        # Increment address. (Note: Delay slot insn.)
                
        jr $ra
        sub $v0, $a0, $v0