A **pointer** in C++ is a variable that holds the memory address of another variable.

A **reference** is an alias for an already existing variable. Once a reference is initialized to a variable, it cannot be changed to refer to another variable.



### Pointer
- It is not necessary to initialize it with a value during declaration.
  ```c++
  int a = 5;
  int *p;
  p = &a;
  ``` 

 

- It can be assigned a *NULL* value.

- It must be dereferenced with a `*` to access the variable's value.
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- Arithmetic operations can be performed on it.
- After declaration, it can be re-assigned to any other variable of the same type. 

  ```c++
  int a = 5;
  int *p;
  p = &a;
  int b = 6;
  p = &b;
  ```

### Reference
- It is necessary to initialize it with a value during declaration.
   ```c++
  int a = 5;
  int &ref = a;

  ```
- It cannot be *NULL*.

- It does not need to be dereferenced and can be used simply by name.

- Arithmetic operations can not be performed on it.
- It cannot be re-assigned to any other variable after its initialization.

Differences between pointers and references in C++

Pointers hold memory addresses and can be reassigned, dereferenced, and null. References are aliases, immutable, and non-null.