Question

Explain addresses in C++ and pointers.

What is the difference between the pointer (*) symbol, the deference operator (&) ?

Include 30 words

Answer 1

An address of a variable defines the location where the variable is stored.

For example :

int a =20;

This means a is a variable which is stored in memory with a value of 20.

To get the address of the variable, we use & operator.

Consider the following segment :

#include <iostream>

using namespace std;

int main() {

int a = 20;

cout << &a;

}

The value which is printed is the address of the variable a. This address which is displayed in the console is a logical address and not physical address. Thus, the logical address is transformed into physical address by operating system using memory management unit ( M.M.U.) and then this physical address in the memory stores the variable a with value 20.

In the above figure, the logical address 0x7ffde192689c is mapped to physical address 1012 of the main memory using MMU.

Difference between (*) symbol and ( & ) operator :

The (*) is called the dereference operator. This is used to return value stored in a particular memory location. In other words, it returns the value that the pointer pointing to a variable is holding.

For example :

int a = 20;

int *p;

p = &a;

cout << *p

This (*) operator will return the value of the variable whose address is stored in pointer p. Thus, *p will give the output 20.

(&) operator is called an address of operator as it stores the address of a variable with a particular value.

In the following segment :

int a = 20;

cout << &a;

&a will give the address of the variable a and it actually tells where in memory the variable a is located with value 20.