Re: Variable values are lost


"NiTiN" asked:

I've got some really simple code that boots the system and displays a
string. I've looked at a couple of examples and I'm aware of the load
to 0x7c00. My jump references are fine but when I try to access
variables, I get nulls instead of the actual data.

I'd try a colon

helloMsg: db 'A'
__
wolfgang
_________________________
Here's the source code:
bits 16
org 0x7c00

jmp start

helloMsg db 'A'

start:
mov al, [helloMsg] ;copy the A
cmp al, 65
jne wrongChar

call printChar ;print the A
jmp end

wrongChar:
mov al, 66 ;print B if wrong character
call printChar

end:
jmp $

printChar:
mov ah, 0eh
;mov al, 65
mov bh, 0h
mov bl, 7h
int 10h
ret

;510 bytes plus the 2 byte signature
zero_padding: times 510 - ($ - $$) db 0

;boot signature
boot_sig: dw 0xaa55


The output I get on running this code is 'B' when it should be 'A'. I
must be missing something.

My setup is VMWare running on Windows, and an NASM compiler.

Any help is appreciated.

Regards,
Nitin


.

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