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I need a concise definition of the "state of an object" in object-oriented programming (for a paper).

For about half of a day I searched for a paper that I can cite on this topic, but I couldn't find one. All the papers I found were mostly general papers on object-oriented programming and they didn't define the state of an object.

I am unsure, but my best guess is something like: The state of an object is defined by the state of the instance variables of the object.

I am searching for a definition of the state of an object and/or a reference on the topic.

(btw, could I refer to the concept as "object state" or is this uncommon?)

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3 Answers 3

You can take a look to (and cite) the book "Object-Oriented Analysis and Design" by G. Booch:

... An object is an entity that has state, behavior, and identity. The structure and behavior of similar objects are defined in their common class. The terms instance and object are interchangeable.

We will consider the concepts of state, behavior, and identity in more detail in the sections that follow. ...

And there is a whole subsection that describes the concept of state:

... From this example, we may form the following low-level definition.

The state of an object encompasses all of the (usually static) properties of the object plus the current (usually dynamic) values of each of these properties ...

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You would also want to keep in mind that the state of an object is an "abstract" entity, as determined by what is observable by the methods. For instance, an object that implements a hash table has as its state, the collection of values stored in the hash table, not all the internal representation details.

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An object-oriented system integrates the terms of code and data using the concept of an "object". An object has state (data) and behavior (code). Hence, the states of object are the instances(variables) inside the object that contains the data.

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This is true but it doesn't sseem to add a lot to the existing answers. –  David Richerby Dec 31 '14 at 18:30
Maybe It'll be easy to understand for someone :) –  Syed MEhran Hussain Dec 31 '14 at 18:57

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