Hello I'm new to programming and new to RobotC. Can any body help me.i want to move my robot to forward direction and when it find the object like wall by sonar sensor then it take decision either turn left or right or reverse. and soo on...please help me .........thanks in advance..

You might try starting here:

http://www.robotc.net/content/lego_curr ... urric.html

Look at the link first. It covers the topics you are asking about in a series of tutorials. If you get confused or have questions, feel free to ask.

There's also a bunch of demo programs that come with robotc but since you're new to programming, I'd start with the online curriculum. It should tell you how to do exactly what you're trying to do.