Object (computer science)

In strictly mathematical branches of computer science the term object is used in a purely mathematical sense to refer to any "thing". While this interpretation is useful in the discussion of abstract theory, it is not concrete enough to serve as a primitive in the discussion of more concrete branches (such as programming) that are closer to actual computation and information processing. There, objects are still conceptual entities, but generally correspond directly to a contiguous block of computer memory of a specific size at a specific location. This is because computation and information processing ultimately require a form of computer memory. Objects in this sense are fundamental primitives needed to accurately define concepts such as references, variables, and name binding. This is why the rest of this article will focus on the concrete interpretation of object rather than the abstract one.

Related Topics:
Mathematical - Computer science - Programming - Information processing - Computer memory - Reference - Variable - Name binding

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Note that although a block of computer memory can appear contiguous on one level of abstraction and incontiguous on another, the important thing is that it appears contiguous to the program that treats it as an object. That is, as far as the program is concerned the object must be free of internal references, because otherwise it is no longer a primitive. In other words, object's private storage details must not be exposed to clients of the object, and must be able to change without changes to client code.

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Objects exist only within contexts that are aware of them; a piece of computer memory only holds an object if a program treats it as such (for example by reserving it for exclusive use by specific procedures and/or associating a data type with it). Thus, the lifetime of an object is the time during which it is treated as an object. This is why they are still conceptual entities, despite their physical presence in computer memory.

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In other words, abstract concepts that do not occupy memory space at runtime are, according to the definition, not objects; e.g., design patterns exhibited by a set of classes, data types in statically typed programs.

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To emphasize that an object actually contains meaningful data, a term data object is sometimes used to refer to such an object.

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