Question

Complete count_bits function. You are given an 32-bits integer stored in $t0. Count the number of 1's in the given number. For example: 1111 0000 should return 4

j main
###############################################################
# Data Section
.data
#

new_line: .asciiz "\n"
space: .asciiz " "
double_range_lbl: .asciiz "\nDouble range (Decimal Values) \nExpected output:\n1200 -690 104\nObtained output:\n"
swap_bits_lbl: .asciiz "\nSwap bits (Hexadecimal Values)\nExpected output:\n75757575 FD5775DF 064B9A83\nObtained output:\n"
count_bits_lbl: .asciiz "\nCount bits \nExpected output:\n20 24 13\nObtained output:\n"

swap_bits_test_data: .word 0xBABABABA, 0xFEABBAEF, 0x09876543
swap_bits_expected_data: .word 0x75757575, 0xFD5775DF, 0x064B9A83

double_range_test_data: .word 945, -345, 0, -3, 55
double_range_expected_data: .word 1200, -6, 104

hex_digits: .byte '0','1','2','3','4','5','6','7','8','9','A','B','C','D','E','F'

###############################################################
# Text Section
.text
# Utility function to print hexadecimal numbers
print_hex:
move $t0, $a0
li $t1, 8 # digits
lui $t2, 0xf000 # mask
mask_and_print:
# print last hex digit
and $t4, $t0, $t2
srl $t4, $t4, 28
la $t3, hex_digits
add $t3, $t3, $t4
lb $a0, 0($t3)
li $v0, 11
syscall
# shift 4 times
sll $t0, $t0, 4
addi $t1, $t1, -1
bgtz $t1, mask_and_print
exit:
jr $ra
###############################################################
###############################################################
###############################################################
# PART 1 (Count Bits)
#
# You are given an 32-bits integer stored in $t0. Count the number of 1's
#in the given number. For example: 1111 0000 should return 4
count_bits:
move $t0, $a0
############################## Part 1: your code begins here ###

############################## Part 1: your code ends here ###
move $v0, $t0
jr $ra

Answer 1

PROGRAM:

.data
   prompt: .asciiz "Enter a number: "
   output: .asciiz "Number of 1's = "
  
.text
main:
   # Prompt to the user to enter a number
   li $v0,4
   la $a0,prompt
   syscall
  
   # Reading input from user
   li $v0,5
   syscall
   move $a0,$v0
  
   # calling count_bits function  
   jal count_bits
  
   # Storing the returned value in $t0
   move $t0,$v0
  
   # Displaying the output to the user
   li $v0,4
   la $a0,output
   syscall
   li $v0,1
   move $a0,$t0
   syscall
  
   # Exiting the program
   li $v0,10
   syscall

# count_bits function
count_bits:
   move $t0,$a0       # Moving function argument to $t0
   li $t1,0       # Count variable
   li $t3,32       # Loop termination condition variable
again:  
   and $t2,$t0,1       # Comparing LSB with 1
   bne $t2,1,count       # If not equal branch to count label
   addi $t1,$t1,1       # If equal increment count variable value
count:   srl $t0,$t0,1       # Shift the input number by 1
   addi $t3,$t3,-1       # Decreasing the loop termination variable value by 1
   bnez $t3,again       # if loop termination not zero continuing the counting process
   move $v0,$t1       # Storing the count value in $v0
   jr $ra           # Returning back to the main function

Please refer to the screenshot of the program for indentation of code:

.data prompt: .asciiz "Enter a number: output: .asciiz "Number of l's = " .text main: ooco Jou WN R # Prompt to the user to enter a number li $v0,4 la $al, prompt syscall # Reading input from user li $v0,5 syscall move $a0, $v0 A oocoo in w N N N HA # calling count_bits function jal count_bits # Storing the returned value in sto move $t0,$v0 # Displaying the output to the user li $v0,4 la $al, output syscall li $v0,1 move $a0,$t0 syscall # Exiting the program li $v0,10 syscall N N N N N N N w w w w w w CO3 on UN POCO GUAWNPOUCO 3o en W w w w w # Moving function argument to sto # Count variable # Loop termination condition variable # count bits function count_bits: move $t0,$a0 li $t1,0 li $t3,32 40 again: and $t2,$t0,1 bne $t2,1,count addi $t1,$t1,1 count: srl $t0,$t0,1 addi $t3,$t3,-1 bnez $t3, again move $v0,$t1 jr fra # Comparing LSB with 1 # If not equal branch to count label # If equal increment count variable value # Shift the input number by 1 # Decreasing the loop termination variable value by 1 # if loop termination not zero continuing the counting process # Storing the count value in $v0 # Returning back to the main function

OUTPUT:

Printing 10 numbers: 12 13 45 46 78 79 31 64 97 21 -- program is finished running -- Enter a number: 5 Number of 1'3 = 2 -- program is finished running -- Reset: reset completed. Enter a number: 15 Number of 1'3 = 4 - program is finished running -- Reset: reset completed. Enter a number: 65535 Number of 1'3 = 16 -- program is finished running -- Reset: reset completed. Enter a number: 32 Number of 1'3 = 1 - program is finished running -- Reset: reset completed. Enter a number: 1 Number of 1'3 = 1 -- program is finished running -- Reset: reset completed. Enter a number: 3 Number of 1'3 = 2 -- program is finished running --