I had tried to use inline assembly instruction to control printer port but
it doesn't work. This is because VC7 (under WinXP) doesn't support
instruction or my code wrong?
My sample code to set all data bit to zero is
__asm{
    mov al,0
    mov dx,0x378
    out   dx,al
This is inserted in main function generated by wizard (win32 console
application).
When I compiled this code ,all pass without problem but at runtime it error
at
"out dx,al" instruction.

Any help will be really appreciated!
Zart

That has nothing to do with VC7. Your problem is that no NT-based OS,
including XP, supports that kind of manipulations from user mode to ensure
the stability and memory protection of the OS. To accomplish what you want,
you'll need to use a special parallel port driver.

--
Tomas Restrepo

As Tom already replied, you just can't do that under XP (or win2k or NT),
and you'll need a special device driver to directly access the printer port.

See http://www.lvr.com/ for articles and drivers and lots more information
about direct control of ports of all kinds.

-cd