Function, Sound, and I/O in MIPS

.data
reply:  .asciiz "The sum is:"

.text

# call function sum(a, b)
    addi    $a0, $0, 4
    addi    $a1, $0, 3
    jal sum
    add $s0, $zero,$v0  #save returned value

#print The Reply
    la  $a0, reply
    li  $v0, 4
    syscall

#print the sum
    li  $v0, 1   #v0= 1 will print $a0
    add $a0, $0, $s0  #$a0 = $s0
    syscall     #print $a0

#make a triumphant horn
    li  $a0, 32
    li  $a1, 5000
    li  $a2, 40
    li  $a3, 100

    li  $v0, 31
    syscall


    j   exit


sum:    addi $sp, $sp, -12
    sw   $ra, 0($sp)
    sw   $t0, 4($sp)

    add $v0, $a0,$a1
    jr  $ra


exit:
    li $v0, 10
    syscall