I am a newbee to RobotC, and I would like to ask how to let the robot perform 2 actions at the same time?
For example: While the robot is moving, the grabber will keep open and close.

RobotC on NXT can run more tasks concurrently.
Within RobotC click on the "TASKS" item on help bar.

Help file on your computer:

C:\Program Files\Robotics Academy\ROBOTC for Mindstorms\RobotC Documentation\NXT\Task Control.htm

Example program with simple task control:

C:\Program Files\Robotics Academy\ROBOTC for Mindstorms\Sample Programs\NXT\NXT Task Test.c

More real-life examples are listed among the bluetooth sample programs.

This is really useful for me, thx very much~~