C++98 Prep - Address / Pointer

Learn how C++ accesses objects through memory addresses.

After this lesson, you should understand:

1. What an address is.
2. What a pointer is.
3. How dereferencing works.
4. Common pointer mistakes.
5. Why pointers are fundamental in C++.

Every object occupies memory.

A pointer allows a program to store and manipulate the address of an object instead of directly storing the object itself.

Main idea:

Object -> lives in memory
Address -> location of the object
Pointer -> stores the address

Take an address:

&object

Store an address:

type* ptr

Access the object through a pointer:

*ptr

Access members through a pointer:

ptr->member

Conceptually:

object ---> memory location

A pointer stores that location.

Example idea:

x contains 10
ptr contains address of x

Dereferencing:

*ptr

means:

go to the stored address
access the object there

5.1 Null Pointer Dereference

A null pointer does not point to a valid object.

Dereferencing it causes undefined behavior.

5.2 Uninitialized Pointer

A pointer that was never initialized contains an unpredictable address.

Always initialize pointers.

5.3 Dangling Pointer

A pointer may outlive the object it points to.

The address remains but the object no longer exists.

This creates dangerous bugs.

5.4 Confusing Pointer with Object

A pointer stores an address.

The object is accessed through dereferencing.

Remember:

ptr   -> address
*ptr  -> object

Pointers are heavily used in:

order management
market data handlers
order books
memory pools
network buffers

Why?

Because copying large objects is expensive.

Passing addresses is usually much cheaper.

You should be able to answer:

1. What is an address?
2. What is a pointer?
3. What does '&' mean?
4. What does '*' mean?
5. What is dereferencing?
6. What is a dangling pointer?
7. Why are pointers useful?

Pointers are variables that store addresses.

The key idea:

Address identifies an object.
Pointer stores the address.
Dereferencing accesses the object.