1) Fundamentals of C Lang.
2) History of C.
3) Datatypes in C.
4) Variables in C.
5) Constants in C.
6) Operators and Enums in C.
7) Decision Making of C.
8) Loop Control in C.
9) Control Flow in C.
10) Array in C.
11) String in C.
12) Function in C.
13) String Functions in C.
14) Recursion in C.
15) Pointer in C.
16) Structure in C.
17) Union in C.
18) File Input/Output
19) Dynamic Memory Allocation.
20) C Pre-processor.
21) Command Line Arguments.
And Many More....