Question

A.6 [5] Using SPIM, write and test an adding machine program that repeatedly reads in integers and adds them into a running sum. The program should stop when it gets an input that is 0, printing out the sum at that point. Use the SPIM system calls described on pages A-43 and A-45.

Short answer

The required code:

.data

str: .asciiz

str2: .asciiz

.text

main:

li $a0,0

loop:

li $v0,4

la $a0,str

syscall

li,$v0,5

syscall

beq $v0,$0,done

add $v0,$0,$v0

j loop

done:

li $v0,4

la $a0,str2

syscall

li $v0,1

move $a0,$s0

syscall

.end

Step-by-step solution

Define the concept.

• The MIPS instruction “la” is used for loading the address.
• The MIPS instruction “li” is used for loading immediately.
• The “branch-on-equal (beq)” is a decision-making instruction in MIPS assembly language. The purpose of using this MIPS assembly instruction “beq reg1, reg2 Label” is going to the statement “Label” if the value of “reg1” is equal to the “reg2”.
• One of the MIPS instructions is “add $t3 $t4 $t5” for add where $t3 = $t4 + $t5.

Determine the calculation

The required code:

.data //this is the data section

str: .asciiz "Please enter the number to be added:"

str2: .asciiz "The Sum:"

.text //this is the text section

main:

li $a0,0 //Initialize the sum is equal to 0

loop:

li $v0,4 //for printing the string

la $a0,str

syscall

li,$v0,5 //for taking the user given input

syscall

beq $v0,$0,done // if zero was taken as a input then end and print the sum

add $v0,$0,$v0 //sum = sum + input

j loop // Jump to the input another number

done:

li $v0,4 // for printing the string

la $a0,str2

syscall

li $v0,1 //for printing the sum

move $a0,$s0

syscall

.end

The output of the code:

Please enter the number to be added: 2

Please enter the number to be added: 3

Please enter the number to be added: 1

Please enter the number to be added: 0

The Sum : 6