Answer : Header files allow you to share common information among various source files.
For a function, we define the function declaration as the return type, the name of the function, and the list of arguments. The function definition is the function declaration followed by the function body. For example:
// function declaration double compute_root[ double a, double b, double c ];
// function definition double compute_root[ double a, double b, double c ] { double delta = b * b - 4 * a * c;
if[ delta < 0 ] { cout