"Adressof" question "int &p" and not "int p"

[CplusplusPower]

Why do i have to use adressof operator to refer to a var in this code?( int &p and not int p?)

why does it do nothing if i use "int p" ?can i have a logic explanation
still learning the adressof thing...

  #include <iostream>
#include <cstdlib>

using namespace std;


void changer(int &p)

{
    p=rand() % 215;
}
#define vectorsize 20
int dudes[vectorsize];

int main()
{
    cout << "dudes : " << endl;
   for(int g=0; g<=vectorsize; g++)

   {
changer(dudes[g]);
       cout << "dude" << g << " is :" << dudes[g] << endl;

   }

    return 0;
}

i know that if i do

cout << &somevariable << endl;

it will give me the adress of that variable(something like 0x02348)
but what is the point of "adressof" in that other code i posted (int &p)?

[Chervil]

Function changer() is passing the parameter by reference.
See the tutorial page:
http://www.cplusplus.com/doc/tutorial/functions2/

[CplusplusPower]

thanks for your reply! sorry if i expressed myself in a confusing way