# A solution to: read and multiply problem

.text

.globl main

main:

move $s1, $ra # Keep the ra safe (stack is another good place)

li $v0,4 # output a prompt

la $a0, msg1

syscall

li $v0,5 # input a number

syscall # User input is now in $vo

move $t0, $v0 # Put the input into a $t0

li $v0,4 # output prompt again

la $a0, msg1

syscall

li $v0,5 # input a second number

syscall # User input is now in $vo

move $a1, $v0 # Put the second input in $a1

move $a0, $t0 # Retrieve the value saved in t0

jal multiply # Note that a0 and a1 contain the args

# so call to multiply is prepared

move $s0, $v0 # Need to put the product someplace safe

# (A spot in memory is a good alternative)

li $v0,4 # output a label for results

la $a0, msg2

syscall

li $v0,1 # output the answer

move $a0, $s0 # Saved answer is an argument to syscall

syscall

move $ra, $s1 # $ra was munged by the call to multiply

j $ra # return

.data

msg1: .asciiz "\nAn integer? "

msg2: .asciiz "\nThe product is: "

.text

multiply: #multiply $a0 by $a1, Bug: a0 can't be < 0

add $t0, $zero, $zero # zero a counter

add $t1, $zero, $zero # zero an accumulator

loop:

beq $t0, $a0, exit # Are we done?

addi $t0, $t0, 1 # If not, Increment counter

add $t1, $a1, $t1 # and add in a1

j loop # Back to top of loop

exit:

move $v0, $t1 # Put answer in the return value register

j $ra # return