Assembly language ? converting ascii to decmial

[matt123]

hello, iam tring to figure out assembly langauge and am having a hard time. I want to write a program purely in assembly that takes in a number in base 10 and converts it to hex octal and binary. Just know how to output to the screen and take in from the keyboard, but once i get the number in I am unable to work with them. i think because they are an ascii string as opposed to integers. trying to convert so i can manipulate them for the conversions to different bases. I may be way off, but am definatley lost and would appreciate any guidance!! Here is the code i have so far, but it does not do waht i want it to:

.section .data
input:
.fill 256 #where i would like to store the converted number, if possible
prompt:
.asciz "Enter a decimal integer:"
prompt_end:
.equ promptlength, prompt_end-prompt

.section .bss
.lcomm number, 40 #number taken in from input, in ascii
.section .text
.globl _start
_start:
nop

######## display prompt string ####################
movl $4,%eax
movl $1,%ebx
movl $prompt,%ecx #string for output
movl $promptlength,%edx
int $0x80

######## get input #################################
movl $3, %eax
movl $0, %ebx
movl $number, %ecx
movl $40, %edx
int $0x80


######## convert from ascii to decmial ##############
# %edi holds current index
# %eax holds number
movl $0, %edi
movl number(,%edi,1),%eax
movl $3, %ecx
loop1:
sub $48, %eax
movl %eax, input
incl %edi
movl number(,%edi, 1), %eax
cmpl %edi, %ecx
jge loop1

########## Output converted number # ###############

movl $4, %eax
movl $1, %ebx
movl $input, %ecx
movl $4, %edx
int $0x80

movl $1,%eax
movl $0,%ebx
int $0x81
~


Thanks!!

[matt123]

Any assembly programmers out there?

[jaymann]

I have not done assem in a while.
Let the compiler help you.
Write your function in c

// test.c
#include <stdio.h>

int main(void)
{
    int i = 0;

    i++;

    return 0;
}

compile

gcc -Wall -S  -masm=att -o test.asm test.c

output

	.file	"test.c"
	.text
.globl main
	.type	main, @function
main:
	leal	4(%esp), %ecx
	andl	$-16, %esp
	pushl	-4(%ecx)
	pushl	%ebp
	movl	%esp, %ebp
	pushl	%ecx
	subl	$16, %esp
	movl	$0, -8(%ebp)
	addl	$1, -8(%ebp)
	movl	$0, %eax
	addl	$16, %esp
	popl	%ecx
	popl	%ebp
	leal	-4(%ecx), %esp
	ret
	.size	main, .-main
	.ident	"GCC: (GNU) 4.3.2 20081105 (Red Hat 4.3.2-7)"
	.section	.note.GNU-stack,"",@progbits

[matt123]

figured out the conversion from acsii to numbers that you can work with mathematically. i will post it here:

######## convert from ascii to decmial ##############
# %edi holds current index
# %eax holds number
movl $0, %edi
movl $0, %ebx
loop1:
xor %eax, %eax #set %eax==0
movb number(,%edi,1), %al #get num for conv
cmp $0xA, %eax #check for nul
je done
sub $48, %al #sub for int
push %eax #save value
movl %ebx, %eax
movl $10, %ecx #multiplier
mul %ecx #multiply current value by 10
pop %ebx #
add %eax, %ebx
incl %edi
jmp loop1
done:
movl %ebx, input
movl %edi, declength


Thanks for the help!