Organizing a C Project

It is a good practice to manage groups of C files in an organized manner. It will be much easier to design, implement and maintain :)

The key point is to separate the function declarations and definitions into multiple files (Not a single C file)

Consider the following scenario :

we have two functions, namely add_int() and multi_int(),

The best practice is to put the declarations into header files:

• int_header.h
  • Declaration of the function prototypes of add_int() and multi_int().

Then put the definitions into seperate C files:

• add_int.c
  • Definition of the function add_int() only.
• multi_int.c
  • Definition of the function multi_int() only.

Finally invoking the functions in the main function.

// main.c
#include <stdio.h>

int main(void) {
        printf("3 + 10 = %d\n", add_int(3, 10));
        printf("3 * 10 = %d\n", multi_int(3, 10));
        return 0;

To compile it using:

gcc -Wall   -c -o main.o main.c

It will show warnings:

As the OS cannot find the definition of add_int() and multi_int(). You have to add the #include:

// main.c
#include <stdio.h>
#include "int_header.h"

int main(void) {
        printf("3 + 10 = %d\n", add_int(3, 10));
        printf("3 * 10 = %d\n", multi_int(3, 10));
        return 0;

So the pre-processor (still remember?) will expand the #include.

To sum up, to compile a large C project, one of the ways is: