; Jade Yu Cheng
; ICS 312
; Assignment 6 Exercise 1
; April 9, 2009
; This program prompts the user to enter a signed 32-bit integer. The program
; prints out the binary representation of the integer.
%include "asm_io.inc"
segment .data
msg1 db "Enter an integer: ", 0 ; msg1
msg2 db "The binary representation is: ", 0 ; msg2
segment .bss
binary resb 32 ; space to store binary representation
segment .text
global asm_main
asm_main:
enter 0,0 ; setup
pusha ; setup
;;; prompt the user the enter a number and treat it as a 32 bit number.
mov eax, msg1 ; print out the prompt message.
call print_string
call read_int ; read a number and store in eax
;;; convert the number to its binary and store it in binary..
convert:
mov ebx, binary ; ebx points to binary
add ebx, 31 ; ebx points to the last bit of binary
convert_loop:
cmp ebx, binary - 1 ; terminate when all 32 bits are written
je convert_loop_end
shr eax, 1 ; right shift by 1, equavilent as divide by 2
jc write_one ; if carry flag is set wirte 1 to ebx
mov [ebx], byte 0 ; otherwise wirte 0 to ebx
dec ebx ; decrement ebx to the next spot to write
jmp convert_loop
write_one:
mov [ebx], byte 1 ; write 1 to ebx
dec ebx ; decrement ebx to the next spot to write
jmp convert_loop
convert_loop_end:
;;; print out binary
print:
mov eax, msg2 ; print out the second message
call print_string
mov ebx, binary ; let ebx points to binary
print_loop:
cmp ebx, binary + 32; terminate when it reaches the end
je print_loop_end
mov eax,0 ; clean up eax
mov al, [ebx] ; move the bit in eax
call print_int ; print it out
inc ebx ; increment the pointer to the next spot
jmp print_loop
print_loop_end:
call print_nl ; print a blank line
popa ; cleanup
mov eax, 0 ; cleanup
leave ; cleanup
ret ; cleanup
