In the scope of "Gang of Four" book patterns split up on three categories by their purpose:  *creational*, *structural*,
and *behavioral*. And also pattens split up by criterion, called scope, specifies whether the pattern applies primarily to
classes or to objects.

**Page 22.:**

    Class patterns deal with relationships between classes and their subclasses. These
    relationships are established through inheritance, so they are static—
    fixed at compile-time. Object patterns deal with object relationships, which can be
    changed at run-time and are more dynamic. Almost all patterns use inheritance to some
    extent. So the only patterns labeled "class patterns" are those that focus on class
    relationships. Note that most patterns are in the Object scope.

## Creational patterns

Creational patterns concern the process of object creation.

#### Scope: Class

   **Factory Method :: Page 107**

    Define an interface for creating an object, but let subclasses decide which class
    to instantiate. Factory Method lets a class defer instantiation to subclasses.

#### Scope: Objects

   **pattern name: Abstract Factory :: Page 87**

    Provide an interface for creating families of related or dependent objects without
    specifying their concrete classes.

   **pattern name: Builder :: Page 97**

    Separate the construction of a complex object from its representation so that the
    same construction process can create  different representations.

   **pattern name: Prototype :: Page 117**

    Specify the kinds of objects to create using a prototypical instance, and create
    new objects by copying this prototype.

   **pattern name: Singleton :: Page 127**

    Ensure a class only has one instance, and provide a global point of access to it.


## Structural patterns

Structural patterns deal with the composition of classes or objects.

#### Scope: Class
     Null

#### Scope: Objects

   **pattern name: Adapter :: Page 139**

    Convert the interface of a class into another interface clients expect.
    Adapter lets classes work together that couldn't otherwise because of incompatible interfaces.

   **pattern name: Bridge :: Page 151**

    Decouple an abstraction from its implementation so that the two can vary independently.

   **pattern name: Composite :: Page 163**

    Compose objects into tree structures to represent part-whole hierarchies.
    Composite lets clients treat individual objects and compositions of objects
    uniformly.

   **pattern name: Decorator :: Page 175**

    Attach additional responsibilities to an object dynamically. Decorators provide a
    flexible alternative to subclassing for extending functionality.

## Behavioral patterns
Behavioral patterns characterize the ways in which classes or objects interact and distribute responsibility.

#### Scope: Class

   **pattern name: Interpreter :: Page 243**

    Given a language, define a represention for its grammar along with an
    interpreter that uses the representation to interpret sentences in the language.

   **pattern name: Template Method :: Page 325**

    Define the skeleton of an algorithm in an operation, deferring some steps to
    subclasses. Template Method lets subclasses redefine certain steps of an
    algorithm without changing the algorithm's structure.

#### Scope: Objects

   **pattern name: Chain of Responsibility :: Page 223**

    Avoid coupling the sender of a request to its receiver by giving more than one object a
    chance to handle the request. Chain the receiving objects and pass the request along
    the chain until an object handles it.

   **pattern name: Command :: Page 233**

    Encapsulate a request as an object, thereby letting you parameterize clients with
    different requests, queue or log requests, and support undoable operations.

   **pattern name: Facade :: Page 185**

    Provide a unified interface to a set of interfaces in a subsystem. Facade defines a
    higher-level interface that makes the subsystem easier to use.


   **pattern name: Flyweight :: Page 195**

    Use sharing to support large numbers of fine-grained objects efficiently.

   **pattern name: Iterator :: Page 257**

    Provide a way to access the elements of an aggregate object sequentially without
    exposing its underlying representation.

   **pattern name: Mediator :: Page 273**

    Define an object that encapsulates how a set of objects interact. Mediator
    promotes loose coupling by keeping objects from referring to each other
    explicitly, and it lets you vary their interaction independently.

   **pattern name: Memento :: Page 283**

    Without violating encapsulation, capture and externalize an object's internal
    state so that the object can be restored to this state later.

   **pattern name: Observer :: Page 293**

    Define a one-to-many dependency between objects so that when one object
    changes state, all its dependents are notified and updated automatically.

   **pattern name: Proxy :: Page 207**

    Provide a surrogate or placeholder for another object to control access to it.

   **pattern name: State :: Page 305**

    Allow an object to alter its behavior when its internal state changes. The object
    will appear to change its class.

   **pattern name: Strategy :: Page 315**

    Define a family of algorithms, encapsulate each one, and make them
    interchangeable. Strategy lets the algorithm vary independently from clients that
    use it.

   **pattern name: Visitor :: Page 331**

    Represent an operation to be performed on the elements of an object structure.
    Visitor lets you define a new operation without changing the classes of the
    elements on which it operates.