Default Value Functions, When declaring a function we can specify a default value for each parameter. This value will be used if that parameter is left blank when calling to the function. This is done by assigning values to the arguments in the function prototypes. If a value for that parameter is not passed when the function is called, the default value is used, but if a value is specified this default value is stepped on and the passed value is used. 

Default arguments must always be the rightmost in a function list i.e. when calling a function with two or more default arguments and an omitted argument is not the rightmost argument in the argument list then all arguments to the right of that argument must be omitted.

Example:

// default values in functions

#include 

using namespace std;

int divide  (int a, int b=2);
int divide  (int a, int b)
{

int r;
r=a/b;

return  (r);

}

int main  ()
{

cout  << divide  (12);
cout  << endl;

cout  << divide  (20,4);
cout  << endl;

return  0;

}

Output

6

5