system calls and library functions

Hi all
I am new to CUDA and just started learning it. I know that CUDA is an extension for C language. So I would like to know that, can we use system calls as well as C library functions such as fopen() with cuda.

Thanks

yes, you can.

Well, you can use system calls in host code, but not within kernels (i.e. the part that actually runs on the GPU).