C Custom Header File

You can create your custom header files in C; it helps you to manage user-defined methods, global variables, and structures in a separate file, which can be used in different modules.

A process to Create Custom Header File in C

For example, I am calling an external function named swap in my main.c file.


void main()
    int a=20;
    int b=30;
    swap (&a,&b);
    printf ("a=%d\n", a);
    printf ("b=%d\n",b);

Swap method is defined in swap.h file, which is used to swap two numbers by using a temporary variable.

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


  • header file name must have a .h file extension.
  • In this example, I have named swap.h header file.
  • Instead of writing <swap.h> use this terminology swap.h for include custom header file.
  • Both files swap.h and main.c must be in the same folder.

Scroll Back to Top