Call by constant reference isn't really a different argument passing method.

It is just call by reference

It combines the const qualifier with the parameter type declaration and has the usual meaning.

A parameter that is declared to have values passed by constant reference

• do get initialized at the call
• are passed by reference (so the parameter is an alias for the argument)
• but the function is not allowed to assign to or otherwise change the parameter's value.

Syntax Example

Call by constant reference:

     int findMax(const int& a, const int& b, const int& c);

We could instead declare findMax to use call by value:

     int findMax(int a, int b, int c);

What is the difference between call by value and call by constant reference?