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Let's start our decision of design patterns by looking

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at the history of patterns. As you know, I like

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to give this sort of historical perspective on how and

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when concepts were defined. In this case, we have to

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go back to 1977, when Christopher Alexander, an American professor

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of architecture at UC Berkeley, introduces the idea of patterns,

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successful solutions to problems, in his book called a Pattern

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Language. The book contains about 250 patterns. And the idea

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is that occupants of a building should be able

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to design it. And the patterns in the book provide

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a way to do that. And this idea of design

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patterns, so, a formal way of documenting successful solutions to

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problems, inspired several other disciplines. In particular, in 1987,

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Ward Cunningham and Kent Beck leveraged this idea of Alexander's

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patterns in the context of an object oriented language.

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And in this specific the language was Smalltalk.

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Some of you might know the language. So what Cunningham

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and Beck did, was to create a 5 pattern

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language for guiding novice Smalltalk programmers. So they did

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an experiment and had several developers using their patterns, and

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the experiment was extremely successful. The users were able to

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create elegant designs using the provided patterns. And in case

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you are interested in reading about it, Cunningham and Beck

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reported the results in the article, Using Pattern Languages for

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Object Oriented Programs, which was published at the

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International Conference on Object Oriented Programming, Systems, Languages, and

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Applications, also called OOPSLA, in 1987. At the

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same time, Eric Gamma was working on his dissertation,

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whose topic was the importance of patterns and

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how to capture them. Between 1987 and 1992, there

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were several workshops related to design patterns. And

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in 1992, Jim Coplien compiled a catalog of C++

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items, which are some sort of patterns, and

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he listed this catalog of patterns in his

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book, which was titled Advanced C++ Programming Styles

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and Idioms. Finally, in 1993 and 1994, there were

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several additional workshops focused on patterns. And this

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workshop brought together many patterns folks, including these

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4 guys, Erich Gamma, Richard Helm, Ralph Johnson,

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and John Vlissides. These guys are also known as

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the gang of 4. And the result of this collaboration was the

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famous book Design Patterns: Elements of

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Reusable Object Oriented Software. So this

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is basically The Book on design patterns. If you want to buy

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a book on design pattern, this is the one you should get.