Important features and of C programming language

1. Function prototype declaration. Like declaring a variable in java, you can also declare a function. It is useful if you are going to call the function before the definition of the function. 
2. C has pointer operator.
3. C doesn't have a string data type. Instead we can use char array. 
4. Structure is a custom data type. It's kind of an "object".
5. "%lf" to format double
6. "%.2f" to format float with 2 digit after a comma. 
7. "%d" to format an integer. 
8.  Store only positiv integer value: unsigned int a;
9. int A[4], printf("%d\n", A); will return the base address (Address of first element)
10. int A[4]; A[0] = 3;  printf("%d\n", A*); will return the value of the first element.
11. Casting an Array to a pointer, now you can access the element without brackets

Creating own library in C

To create your own library in C please follow this steps:

1. Create two folders, name the first folder 'utils' and the second folder 'headers'
2. Write your functions in a .c file and put it in the utils folder. 
3. Create a .h file with the same name as the .c file that contains the functions. Put the header files in the headers folder. The .h file should contains following code. 
4. Open terminal and go to the utils folder and compile the .c files using this command gcc -c *.c
5. Build the library by putting all the .o files in an archive using this command ar -cvq yourlibraryname.a *.o library name starts with lib, and don't froget the .a extension at the end
6. Now you can use the library in your program by adding a file header #include "headers/yourLibraryName.h"
7. Compile your program by providing the library name gcc -o programName programSourceCode.c utils/libraryName.a
8. If youre using C-Lion IDE, you can simply add your .c and .h paths to the CMakeList.txt like this: