User defined Header files in C

We know that built-in header files contain the prototypes for many useful functions. We can also create our own header file with custom function.

For example – Let us create one header file called mul.h which contains the function sum. This function will return the sum of 2 arguments that we pass.

Source code of Sum.h header file is given below.

int mul(int a, int b)

{

return (a*b);

}

Source code of abc.c is given below. Please note how we have included above header file in abc.c and we have called mul function which is defined in mul.h

#include <stdio.h>

#include "mul.h"

int main()

{

printf("%d", mul(3,4));

}

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