efficiency in passing a value to a function

[Shriramana Sharma <jamadagni@gmail.com>]

Hello.

Is providing an input to a function by constant reference more efficient 
than passing it by value? In what way.

For ex:

int addOne ( const & int inValue ) { return inValue + 1 ; }

vs:

int addOne ( int inValue ) { return inValue + 1 ; }

or:

void printThis ( const & int inValue ) { cout << inValue ; }

vs:

void printThis ( int inValue ) { cout << inValue ; }

I think passing as const & would be more efficient since passing by 
value would involve copying the value whereas passing by const & would 
skip this step. Am I right? Or is there something else?

Thanks in advance.

Shriramana Sharma.