how can i intereact with os's kernel in c language

Which OS? Linux? MacOSX? Windows? Android?

What are you trying to do?
Are you writing a software application and are hindered by a specific problem?
Just getting information from a running system?
Trying to change system's behavior?

Are you sure you need to interact with the kernel? Maybe there's a high-level library call that's a simple way to do whatever you're trying to do.