// This is the header file for the maths module
// example. The header file will contain: 
// - any #defines
// - function prototypes and any comments

#define PI 3.14

// Function prototype for a function that 
// calculate the square of a number:
int square(int number);

// Function prototype that calculates the sum of 
// of two numbers
int sum(int number_one, int number_two);