Using Extern change the charecteristic of the PRG.  For example, using
EXTERN in a procedure turns it into a function and using EXTERN in a
function creates compiler error.

Also, what are the differences between CDECL (C calling convention)
and STDCALL (Standard for the Windows 32bit API)?

I have a DLL compiled by Studio with a function
disableMagstripeDevice().  Dependency Walker shows this function as
_disableMagstripeDevice@0().  How this function should be called?

Many thanks,

-Itai

Itai,

>Using Extern change the charecteristic of the PRG.  For example, using
>EXTERN in a procedure turns it into a function and using EXTERN in a
>function creates compiler error.

You can't use EXTERN inside a Procedure, Function, or Method. Just like the 
DLLFUNCTION command (which it basically replaces), the pre-compiler will 
convert the EXTERN command into a separate (DLL) Function.

>Also, what are the differences between CDECL (C calling convention)
>and STDCALL (Standard for the Windows 32bit API)?

Short version: With CDECL, the caller cleans up the stack, while with 
STDCALL, the function you call cleans up the stack before returning.

Long version: https://en.wikipedia.org/wiki/X86_calling_conventions

>I have a DLL compiled by Studio with a function
>disableMagstripeDevice(). Dependency Walker shows this function as
>_disableMagstripeDevice@0(). How this function should be called?

Try either way, and see which one works, but I guess the name was changed by 
"name mangling", and you probably need to use the second version.

See also: https://en.wikipedia.org/wiki/Name_mangling

Hope that helps,

Andreas

Andreas Gehrs-Pahl
Absolute Software, LLC

phone: (989) 723-9927
email: Andreas@AbsoluteSoftwareLLC.com
web:   http://www.AbsoluteSoftwareLLC.com
[F]:   https://www.facebook.com/AbsoluteSoftwareLLC

Thank you, Andreas.
I cannot use the second option because xBase++ cannot handle a
function that include the @ character.
Using the first option errs: Function is not declared.
I should find another scanner with a well written API or ActiveX.
Again, thank you for the quick response.
Yes, it helps!

-Itai

Itai,

>I cannot use the second option because xBase++ cannot handle a
>function that include the @ character.

That's not true. DLLCall() and DLLPrepareCall() can handle those kinds of 
functions just fine.

You might have to use those functions directly, instead of using the 
pre-processor to convert EXTERN or DLLFUNCTION to create a separate 
function.

One way to easily accomplish this, is to use the command version with the 
non-mangled function name and use the /p compiler option to retain the *.ppo 
file. Then you can copy the created code from the *.ppo file into your *.prg 
file, replacing the function name with the mangled one.

Hope that helps,

PS: It's Xbase++ (not xBase++) 

Andreas

Andreas Gehrs-Pahl
Absolute Software, LLC

phone: (989) 723-9927
email: Andreas@AbsoluteSoftwareLLC.com
web:   http://www.AbsoluteSoftwareLLC.com
[F]:   https://www.facebook.com/AbsoluteSoftwareLLC

Thank you, Andreas!
WORKING GREAT!!!!
-Itai