Hi,
Each channel is indvidually programmable as input or output, as stated by the user manual:
http://digital.ni.com/manuals.nsf/websearch/84D33F396EA5C8A286256F51007A7078?opendocument
You can view this functionality using the C:\Program Files\National Instruments\LabVIEW 7.1\examples\daqmxbase\USB-600x Interactive Control.vi and change each line to input or output on the same port at the same time. You can view the code for this interactive utility or the examples for DIO to get started in programming it.
Have a Great Day!
George