fact:  sub   $sp, $sp, 8          # Make room for 2 items on stack
       sw    $ra, 4( $sp )        # Return address
       sw    $a0, 0( $sp )        # Input argument, saved for multiplication

       slt   $t0, $a0, 1          # n < 1?
       beq   $t0, $zero, L1       # Prepare to call function again

       add   $v0, $zero, 1        # Return 1
       add   $sp, $sp, 8          # Pop two items; you don't restore them (why?)
       jr    $ra                  # Return to caller

L1:    sub   $a0, $a0, 1          # Perform recursion
       jal   fact

       # Return point from recursion

       lw    $a0, 0 ( $sp )       # Restore n to value before recursive call
       lw    $ra, 4 ( $sp )       # Return address before recursive call
       add   $sp, $sp, 8          # Restore stack pointer

       mul   $v0, $a0, $v0        # return ( n * fact ( n - 1 ) )
       jr    $ra                  # Return to caller

main:
       sub   $sp, $sp, 4
       sw    $ra, 0($sp)
       add   $a0, $zero, 5
       jal   fact
       lw    $ra, 0($sp)
       add   $sp, $sp, 4