Hello donatap,
Take a look at the example folder of NI-DAQ:
C:\Program Files\National Instruments\NI-DAQ\Examples\VisualC\Do
In this folder all kinds of examples are listed on how to do Digital Output. Maybe this can help you understand the driver better.
Hope this helps.
Best Regards,
RikP
Application Engineering
National Instruments
Rik Prins, CLA, CLED
Software Development Engineer