What is a class in the system design?

Class diagrams are the blueprints of your system or subsystem . You can use class diagrams to model the objects that make up the system, to display the relationships between the objects, and to describe what those objects do and the services that they provide. Class diagrams are useful in many stages of system design.

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What defines the design of all classes?

There are three ways to design classes: by composition, via inheritance, and via interface . Composition (or aggregation) is achieved by using existing class as a part of a new class. For example, the ArrayStack class includes an array of objects. Inheritance allows you to define a new class in terms of an old class.

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