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Design patterns
The advances of structured and O-O programming still underpin
the way in which systems are written today. However, as the software
industry grew, the task of teaching each new wave of programmers how
to program efficiently has led to a new level of abstraction. In 1995, four
software engineers - Erich Gamma, Richard Helm, Ralph Johnson, and
John Vlissides - got together and identified what they called “design pat-
terns” ( B.4.16 ). These are standard patterns in software that everybody
uses to perform a number of simple tasks.
One example is the “Observer pattern.” This ensures that when one
object changes its state, all of its dependents are notified and updated
automatically. They identified twenty-two patterns they called by easy-to-remember names. Apart from
Observer , other example patterns are Factory , Decorator , Interpreter , and Visitor . Their topic on design patterns
has become one of the best-selling and most-cited topics in computer science. It established a ixed vocab-
ulary for talking about O-O software at a level above program code, so that programs - and programmers -
became more transferable, understandable, and accurate.
B.4.16. The “Gang of Four”: Ralph
Johnson, Erich Gamma, Richard Helm,
and John Vlissides.
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