The C Keywords must be in your information because you can not use them as a variable name.

You can't use a keyword as an identifier in your C programs, its reserved words in C library and used to perform an internal operation. The meaning and working of these keywords are already known to the compiler.

C Keywords List

A list of 32 reserved keywords in c language is given below:

auto double int struct
break else long switch
case enum register typedef
char extern return union
const float short unsigned
continue for signed void
default goto sizeof volatile
do if static while

Example Where and How Keywords are Used in the Program

Example:
#include<stdio.h>

int main()
{
    float a, b;
    printf("Showing how keywords are used.");
    return 0;
}

In the above program, float and return are keywords. The float is used to declare variables, and return is used to return an integer type value in this program.

Keywords in C - Video Tutorial

To understand C Keywords in more depth, please watch this video tutorial.