Clipping occurs when audio signals represented as integers exceed the maximum or minimum possible value for an integer. 24 bit integers can store a much larger range of numbers than 16 bit integers, but can still get maxed out.
Your audio interface works with integers, both going in and coming out of the DAW. However, internally a DAW works with floating point numbers. The conversion happens when importing/recording or exporting audio. This includes reading/writing wav files stored in the audio folder. wav files are stored in integer format.
Floating point numbers can represent a MUCH larger range of values. Once audio data is within the DAW software, it is extremely difficult (effectively impossible) to get clipping.
However, as others have noted, some plugins may react badly to large floating point numbers. I'm not sure why - maybe they make some assumptions about the size of the incoming signal. The meters in Sonar must make similar assumptions. So best to keep the signal amplitude in the sane range, but behind the scene, insanity is tolerated!
Cheers, Peter.
p.s. It just occurred to me, why don't audio interfaces convert analog audio input to floating point numbers? Probably because the typical analog/digital conversion chips produce integers (16/24/32 bit).