C Programming Language by Kernighan and Ritchie is the basics of C Language

I would strongly reccomend this book as well as  it is a relatively compressed book for all the knowledge it contains and was written by the creators of c. I like the practicality of the book as it presents practical 'programming' problems. A  sufficient understanding of computer systems organisation and architecture(low-level)  is as a prerequisite as the author does explain in the intro that it is not written for beginners.