Variables are created by:

• int a=5; (we have some area in memory with value 5 and we refer it with name 'a')
• We need to ask where is this variable located in memory, we have an operator(&a) called 'address of' which stores the address of varialbe 'a'.
• address are stored with 12 characters of hexadecimal numbers. ex. 0xAEC034523823 . storing this number requires 12.4=48 bits of memory. (becuase each hexadecimal number is from 0 to 15(F), and 4 bits are sufficient to store any hexadecimal number)
• since 4 bytes (32 bits) are sufficient for storing address we can use integer data type to store address of variable.
• pointers points/stores address of varialbe so they are declared and assigned by : int * p=&a; (here p is pointer varialbe which will store address of varialbe 'a')

Reference is an alias or another name for any given variable.
The way we create an alias is:

	#include<iostream>
	int main()
	{
	int a=5;
	int & b=a;  //here b is an alias of a, now we can access the variable a by two methods, a or b.
	std::cout<<a<<'\t'<<b;
	//(int &b, int & b , int& b - all are same)	
	}

Behind the scenes references uses pointers, but we don't need to go to that level.

1. References are majorly used when we are passing large amount of data in a function, when we pass data inside a function we generally copy that data to parameter variables. Have a look below the use of references:

	#include<iostream>
	int add(int &a, int &b)
	{
	int c=a+b;
	return c;
	}
	
	int main()
	{
	int x=50;
	int y=40;
        std::cout<<add(x,y);     // in this way the data 50 and 40 is not copied in any variable, and it saves memory, it is useful when passing billions of data points in a function or passing a vector. It helps in saving memory.
        return 0;
	}

1. Like pointers any changes made to alias does not remains inside the function only, and changes will reflect outside the function as well. code:

   	#include<iostream>
   	void increment(int &a)
   	{
   	a++;
   	}
   	int main()
   	{
   	int x=5;
   	increment(x);
   	std::cout<<x; //it will print 6 
   	return 0;
   	}
   
   

2. Location we set to alias/reference is permanent, once we set an alias, we can not make it alias to something else.

   	int a=3;
   	int c=30;
   	int &b=a;
   	b=c; // this statement will store value of c in b which points to address of a, so a=30=b=c
   	return 0;
   

3. Alias and original variable has same address and it can be checked by following code:

    	#include<iostream>
   	int main()
   	{
   	int a=5;
   	int &b=a;
   	std::cout<<&a<<'\t'<<&b;
   	return 0;
   	}