Where They get Useful  Function Arguments ?

Of course, until you start using them in functions, both pointers and references usually seem to have little, er, point. The classic use of pointers is in a swap function. Suppose you want to write a function that has the potential to operate on its arguments, permanently changing their values. You will need to use pointers or references. Here’s the pointer version:void swap_with_ptrs(int *p1, int *p2) {     int temp = *p1;     *p1 = *p2;     *p2 = temp;}Here is the version that uses references:void swap_with_refs(int &aRef, int &bRef) {     int temp = aRef;     aRef = bRef;     bRef = temp;}These two functions look similar and in fact do the same thing.I’ve gotten into trouble with one or two people by saying this, but in my opinion, both of these version implement what, in other languages, you would call pass by reference; they do what in BASIC or FORTRAN you would do by specifying a reference variable, which lets the function or subroutine change the value of the argument passed to it. In C, using pointers was the only way you could “pass by reference.”Technically, what’s really going on with the pointer version is that it’s passing pointers by value, but the effect is exactly the same as passing integers by reference.Moreover—and I will go out on a limb to say this—to implement the reference version, the compiler will almost certainly use pointers and de-reference them under the cover. Why? Because there’s no other way to do it, at least no obvious way.But... if the two versions produce exactly the same effects at runtime, how do you choose between them?I’m going to come down on the side of using references, because even though the implementations are identical, there is one other difference: When you call the function at runtime, the version with references passes the variables directly, rather than making you use the additional operator needed to get the addresses (&). So, it involves slightly less syntax.int big = 100;int little = 1;swap_with_ptrs(&big, &little);  // swap big and littleswap_with_refs(big, little);    // swap again!References were originally added to the C++ language to make it easy and efficient to write copy constructors. But, in addition for functions like swap, I would recommend using references as much as possible rather than pointers.Pointers aren’t going to go away any time soon, because C++ code often contains thousands of lines of C legacy code. Furthermore, C++ programmers are just in the habit of using them.