.text
        .globl  __start
__start:
        li      $v0, 4           # mesg1 asking for a number
        la      $a0, msg1
        syscall
        li      $v0,5           # system call that reads an integer
        syscall 
        move    $a0, $v0
        jal     countbits

        move    $t2, $v0
exit:   li      $v0, 4          # print mesg2
        la      $a0, msg2
        syscall

li      $v0,1                   # print countbits
        move    $a0, $t2
        syscall
        li      $v0,4           # print an end of line
        la      $a0, cr
        syscall
        li      $v0,10          # exit
        syscall

countbits: addi $v0, $zero, 0
           beq  $a0, $zero, done
           bge  $a0, $zero, rec
           addi $v0, $v0, 1
    rec:   addi $sp, $sp, -8
           sw   $ra, 4($sp)
           sw   $v0, ($sp)
           sll  $a0, $a0, 1
           jal  countbits
           lw   $ra, 4($sp)
           lw   $s0, ($sp)
           addi $sp, $sp, 8
           add  $v0, $v0, $s0
    done:  jr   $ra

.data

msg1:   .asciiz "Enter a integer number:  "
msg2:   .asciiz "Number of 1's in the number  =   "
cr:     .asciiz "\n"