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Let's start with objects. An object is a

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computing unit organized around a collection of state

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or instance variables that define the state of

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the object. In addition, each object has associated

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with it a set operations or methods that

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operate on such state. So what that means

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is that operations and methods read and write

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instance variables. And in traditional object orientation, we say

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that operations are invoked by sending a message

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to the appropriate object, which is what we call

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normally a method implication. So now that we define

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what an object is, state variables, or attributes, and

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operations or methods, let's see what a class is.

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A class is basically a template. A blueprint, if

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you wish, from which new objects, which is what

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we call instances of the class can be created.

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And notice that the fact of having a blueprint for

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objects that allows us to create as many objects as

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we want can further reuse, and also contribute to make

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the code more readable, understandable,

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and therefore ultimately more maintainable.