The back-of-chapter problems in Jeyapoovan’s book are excellent for testing your retention.
Breaking down code into reusable modules.
Mastering one of C’s most powerful (and challenging) features. Structures and Unions: Creating custom data types.
While the temptation to find a free PDF online is high, please keep a few things in mind:
Setting up your environment and understanding the basic syntax.
Managing collections of data efficiently.