tuxduino:
Those two constants are not a C++ keyword, but were added to Arduino a while ago:
No, that's false. The linked thread only discusses that they should be highlighted in the IDE.
I looked here:
on section 2.12
I'd say use true/false if you are returning a boolean, and use 0/1 if you are returning a number. Same for the testing --- use ! if it's a bool, ==0 if it's an int.