Need help with Printing Screen

[Zhane]

I am able to put values into AL and print using 'CALL PrintCharacter'

but I couldnt print 'msg' with 'Call PrintString'

am I missing anything here? please help


----------------------

cpu 686

use16

segment .text
%define TC_BIOS_KEY_ENTER 1ch

GLOBAL Logger
GLOBAL g_uLoggerCodeSize
GLOBAL g_uCallAskPasswordDeltaOffset

push ax
push es

push ds
pop es ; put ds into es

MOV ESI, msg
Call PrintString

.keypress:
;wait for keypress
mov ah,0
int 16h
pop es
pop ax
.exit:
pop bp
ret ; cdecl

;----------- Procedures --------------

PrintCharacter: ;Procedure to print character on screen
;Assume that ASCII value is in register AL

PUSHA
MOV AH, 0x0E ;Tell BIOS that we need to print one charater on screen.
MOV BH, 0x00 ;Page no.
MOV BL, 0x07 ;Text attribute 0x07 is lightgrey font on black background
INT 0x10 ;Call video interrupt
POPA
RET ;Return to calling procedure


; ---- Dont work ----
PrintString: ;Procedure to print string on screen
;Assume that string starting pointer is in register SI

PUSHA
next_character: ;Lable to fetch next character from string
MOV AL, 88 ; X
CALL PrintCharacter

MOV AX, [ESI] ;Get a byte from string and store in AL register
INC ESI ;Increment SI pointer
OR AX, AX ;Check if value in AL is zero (end of string)
JZ exit_function ;If end then return
CALL PrintCharacter ;Else print the character which is in AL register
JMP next_character ;Fetch next character from string

exit_function: ;End label
MOV AL, 87 ; W
CALL PrintCharacter

POPA
RET ;Return from procedure

msg dw 'Hello, world!',0xa ;our dear string

[olivthill2]

OR AX, AX	 ;Check if value in AL is zero (end of string)
JZ exit_function ;If end then return
...
msg	dw	'Hello, world!',0xa	;our dear string

I see a line feed character (0x0A) at the end of your string, but I don't see a null (binary zero) character. It's different from the C language where a null character is automatically appended to an array of characters.
But I don't know if this is the cause of your problem.
Try to see what happens with only the first character, when you remove JMP next_character.

And please, use PHPBB tags, i.e. write [code] before, and [/code] after your lines of codes when you post them here.

[Bob Walsh]

Apparently what we're "missing" is that this is supposed to be a module
linked with gcc(!). Yeah, I know it's 16-bit code. There are some kernel
services that will put us in vm86 mode - dosemu apparently does it that
way. I'm waiting for further details on what's in the "other module"
that this is linked against. See c.l.a.x.

...

>> msg dw 'Hello, world!',0xa ;our dear string

The "dear string" comment ought to have been a tipoff. I first saw this
comment in an example in the assembly "howto" by Konstantin Boldyshev.
I've copied it around a bit - I suppose other people have, too, but
that's where it "comes from", AFAIK.

> First I have no idea why you precede all characters with an "X"
> and end with "W", if the code is 16 bit, then you better use:

Just a "debugging test", I think. Apparently it works(?). There's a
"Linux Real Mode Interface" library available at SourceForge - this
*may* be what Zhane's using.

> MOV SI,msg ;why ESI ?

Apparently si gets a complaint from ld. I suspect he may want si, but
may need to "do something different" to let gcc/ld know it's "okay".
Perhaps a 16-bit section ("use16" in the section declaration, rather
than "freestanding")... Or ????



http://www.techstore.ie/Design-Print

[Alex Chadiak]

The screen consists of three negatives, one in cyan, one in magenta and the other in yellow. There is one unmasked colour print and one masked print. The image printed is a photograph of a number of objects on a table top, including a green handbag, a travel clock, a pair of white gloves and two silver sailing ship ornaments.