ghostrssThe Little Book of C
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.)
And the K&R reference is useful too. It's a small book about a small language that does not have many features and maps to very basic concepts on hardware that really only does very basic things.