pointer in c++

1. shared_ptr 1.1 when last use goes out of scope, object on free store is deleted 1.2 make_shared improves performance

2. unique_ptr 2.1 less overhead than shared_ptr 2.2 Not copyable(but movable)

use a pointer 1. Member variable, lifetime tied to the class 2. A way to observe/access something without impact on its lifetime - a pointer back to your owner or container - a list of the resources your’re using 3. Shared access to an object on the free store - with no single owner