Another very fine online reference for someone new to C is Beej's Guide to C Programming: https://beej.us/guide/bgc/
(Here is a reference to K&R, the standard first reference to C, because I am obligated to make such a reference.)
(Here is a reference to K&R, the standard first reference to C, because I am obligated to make such a reference.)
https://progforperf.github.io/Expert_C_Programming.pdf
If you’re a C programmer, old or new, and haven’t encountered this book: Stop What You Are Doing And Go Read It! It’s amazing.