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Correct way to declare and define a function in C

By: IncludeHelp, on 01 MAR 2017

Learn: How to declare and define the functions in C language, what is the correct and incorrect way to declare and define functions?

A function should be declared before the main() function (in the global section), so that we can use it within the main() or other user define function.

It is a wrong practice to declare and define the function together, like this:

#include <stdio.h>

/*Declaration & Definition*/
int add(int a,int b){
	return (a+b);
}
int main()
{
	/*function calling*/
	printf("%d\n",add(10,20));
	return 0;
}

Correct method

You should declare a function before the main() separately and define the function after the main(), like this:

#include <stdio.h>

/*Function declaration*/
int add(int a,int b);

int main()
{
	/*function calling*/
	printf("%d\n",add(10,20));
	return 0;
}

/*Function definition*/
int add(int a,int b){
	return (a+b);
}