6.2. Argument Passing

As we’ve seen, each time we call a function, its parameters are created and initialized by the arguments passed in the call.

As with any other variable, the type of a parameter determines the interaction between the parameter and its argument. If the parameter is a reference (§ 2.3.1, p. 50), then the parameter is bound to its argument. Otherwise, the argument’s value is copied.

When a parameter is a reference, we say that its corresponding argument is “passed by reference” or that the function is “called by reference.” As with any other reference, a reference parameter is an alias for the object to which it is bound; that is, the parameter is an alias for its corresponding argument.

When the argument value is copied, the parameter and argument are independent objects. We say such arguments are “passed by value” or alternatively that the function is “called by value.”