Hello all. This past semester I took assembly programming. The programs in class were done on windwos machines and now I am trying to write some assembly on my linux machine, which has an intel 64bit processor. I am having a problem converting integers to ascii for output. I am using the same routine we used in my class which adds 30h to each digit and store it in a string but I am not getting the approptiate output. The number I am trying to output is 15 but I get D and a small black circle with a white question mark insid it. Does anyone know what is causing this? Is it an issue with using 64bit processor or is it an encoding issue in linux?

an intel 64bit processor

Do you mean an actual 64 bit CPU? Like an Itanium? Or do you mean a normal x86 CPU with the EMT64 extensions?

it is a core 2 duo so if I remember correctly it has the 64 extensions. As for the code I will have to post it tonight. I do not have it with me right now.

Here is the code I have written. All I am trying to do at this point is add two numbers and convert the result to ascci and print to screen.

section	.data

msg	db	'Hello, world! this is jason.',0xa	;our dear string
len	equ	$ - msg			;length of our dear string
MAXSTR	equ	256d

section .bss
num1:	resd	1
num2:	resd	1
resultSt:	resb	MAXSTR
strAddr: 	resd	1
strLen:		resd	1
section	.text
    global _start			;must be declared for linker (ld)

_start:					;tell linker entry point

	mov eax, 5d
	mov ebx, 10d
	add eax, ebx
	mov dword [num1], eax
	
	lea esi, [num1]
	lea edi, [resultSt]
	call int2ascii
	
	lea esi, [resultSt]
	call printString

	;mov 	edx,len	;message length
	;mov	ecx,msg	;message to write
	;mov	ebx,1	;file descriptor (stdout)
	;mov	eax,4	;system call number (sys_write)
	;int	0x80	;call kernel

	mov	eax,1	;system call number (sys_exit)
	int	0x80	;call kernel

;********************procedure to convert int to ascii********************
;integer to be converted in esi, destination string in edi
;*************************************************************************
int2ascii:
	pushad		;push registers
	pushfd		;push flags
	cld		;clear direction flag
	
	mov eax, [esi]	;load number to eax
	mov ecx, 0h	;zero ecx for digit counter
	mov ebx, 10d	;move divisor of 10 to ebx
nextOut:
	mov edx, 0h	;zero edx for high order word of division
	div ebx		;divide by 10
	push edx	;push the remainder
	inc ecx		;count digit
	cmp eax, 0h	;compare eax to 0
	jg nextOut	;if greater jump to nextOut

charOut:
	pop eax		;get number from stack
	or eax, 0030h	;or with 30h to get int
	stosb		;store in destination string
	dec ecx		;decrease chars to print by one
	jnz charOut	;if CX > 0 go to charOut
	mov al, 0d	;mov 0 to al
	stosb		;terminate string
	popfd		;restore registers and flags
	popad
	ret

;***************************printString procedure**********************
;Given	 : string to print in esi
;process : print string using linux sys_call to print to screen
;	   no registers or flags are affected
;returns : nothing
;**********************************************************************
printString:
	pushad			;save flags and registers
	pushfd
	cld			;clear direction flag to print forward
	mov dword [strAddr], esi	;save string address
	mov dword [strLen], 0		;set length to 0

whileChar:	
	cmp BYTE [esi], 0		;compare string element to 0
	jz endWhileChar		;if zero end loop
	inc dword [strLen]		;increment string length
	inc esi			;increment esi
	jmp whileChar		;jump to start of loop

endWhileChar:
	mov edx, strLen
	mov ecx, strAddr	;string address
	mov ebx, 1		;stdout
	mov eax, 4		;syscall numbedr for write
	int 0x80		;call system

	popfd			;restore flags and registers
	popad	
	ret		;return to calling procedures

well I found one problem. I have to put the size for the variable in the print routine before making the syscall to write.
mov edx, dword [strLen]
mov ecx, dword [strAddr]

However, now I am getting no output after converting the number to a string. I am using nasm by the way.

ok I made one of those boneheaded mistakes. I made the changes mentioned in my last post and I was getting no output. I looked at the code for thirty minutes before noticing that I had commented out the call to the conversion procedure. Everything is working as it should noe. Thanks for all your help.

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