some queries for pointers and imputs

[cable]

(1)
 void exam(int &x){
}

//call the function
exam(x);

what is the meaning of this?
shouldn't be say

 void exam(int *x){
}

//call the function
exam(&x);

(2)
if we call a function like this

(2)
void exam2(istream cin){
}
exam2(cin);

//call it
[/code]
cin use the iostream library but when we declare the function we use istream which
iostream inherit from it , what would be the different if we was declaring the function with iostream library
thanks

[tabstop]

"int &" is a type, called "reference to int". It is not the same as "pointer to int".

For the second, there is an issue related to the first: you don't want to create a new istream; you should instead pass a reference to an istream (many istreams, like cin, cannot be copied). iostream inherits from both istream and ostream; if the function was expecting an iostream&, it would not be able to accept an istream& object -- which means you wouldn't be able to pass (say) cin into it, since cin is an istream object not an iostream object. (However, if you keep the istream& parameter, you can pass in any child object, like an iostream& object.)