Dividing a C program into multiple files demonstration.

main.c

#include <stdio.h>

/* Extra files headers */
#include "types.h"
#include "special_functions.h"


void helper_function();

/* Main program */
int main() {
  struct struct_type my_struct = { .val1 = 1 , .val2 = 1};
  union union_type my_union = { .n = 1 };

  special_function(my_struct, my_union);
  helper_function();
  printf("Success!\n");
  return 0;
}


void helper_function() {
  printf("helper function: I'm called from main!\n");
}

main_single_file.c

#include <stdio.h>

/* Type definitions */
typedef int my_type;

struct struct_type {
  my_type val1;
  int val2;
};

union union_type {
  my_type n;
  char c;
};


/* Extra function prototypes */
void special_function(struct struct_type my_struct, union union_type my_union);
void helper_function();


/* Main program */
int main() {
  struct struct_type my_struct = { .val1 = 1 , .val2 = 1};
  union union_type my_union = { .n = 1 };

  special_function(my_struct, my_union);

  printf("Success!\n");
  return 0;
}


/* Extra function definitions */
void special_function(struct struct_type my_struct, union union_type my_union) {
  helper_function();
}


void helper_function() {
  printf("helper function: I'm called by special_function!\n");
}

makefile

all: main.c special_functions.c types.h
	gcc main.c special_functions.c -o main

Multiple file C program.md

Dividing a C program into multiple files

Example initial file: main_single_file.c.

Divided into several files:

• main.c
• types.h
• special_functions.c
• special_functions.h

Tutorial instructions here.

special_functions.c

#include <stdio.h>

#include "types.h"

static void helper_function();

/* Extra function definitions */
void special_function(struct struct_type my_struct, union union_type my_union) {
  helper_function();
}


static void helper_function() {
  printf("helper function: I'm called by special_function!\n");
}

special_functions.h

#ifndef SPECIAL_FUNCTIONS_H
#define SPECIAL_FUNCTIONS_H

/* Extra function prototypes */
void special_function(struct struct_type my_struct, union union_type my_union);

#endif

types.h

#ifndef TYPES_H
#define TYPES_H

/* Type definitions */
typedef int my_type;

struct struct_type {
  my_type val1;
  int val2;
};

union union_type {
  my_type n;
  char c;
};

#endif