You can create yourcustom header file in C; It helps you to manage user-defined methods, global variables, and structures in a separate file, which you can use in different modules.

A Process to Create Custom Header File in C

For example, in the following code, I am calling an external function namedswap in mymain.c file.

Example:

#include<stdio.h>#include"swap.h"void main(){    int a=20;    int b=30;    swap (&a,&b);    printf ("a=%d\n", a);    printf ("b=%d\n",b);}

The swap method is defined in theswap.h file is used to swap two numbers using a temporary variable.

Example:

void swap (int* a, int* b){    int tmp;    tmp = *a;    *a = *b;    *b = tmp;}