COUPLING

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Coupling is a measure that defines the level of inter dependability among the modules of a program.

It tells at what level the modules interact and communicate with each other.

The lower coupling is better for a program.

Two modules with a high coupling are strongly inter connected to each other.

Two modules with low coupling are not depended on each other.

Loosely coupled s/m makes modules relatively independent.

A good design will have low coupling.

Thus, interfaces should be carefully specified in order to make low coupling.

coupling is measured by no. of inter connections btw modules.

Eg: no.of datas shared.

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TYPES OF COUPLING

Strength of coupling varies from lowest coupling(best) to strongest coupling(worst).

Different types of coupling are as follows:

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DATA COUPLING

The dependency btw Two modules that is A and B is said to be data coupled if their dependency is based on the fact that they communicate by only passing of data.

Other than communicating data the two modules are independent.

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STAMP COUPLING

Stamp coupling occurs when complete data structure is passed from one module to another.

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CONTROL COUPLING

Two modules are said to be control coupled if one of them decides the function of another for changing its flow of execution.

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EXTERNAL COUPLING

The form of coupling in which a module has a dependency to other module,external to the s/w being developed for a particular type of h/w.

This is basically related to the communication to external tools and devices.

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COMMON COUPLING

When multiple modules have read and write access to some global data,it is said to be common coupling.

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CONTENT COUPLING

Content coupling occurs when module A changes the content of module B or a control is passed from one module to the middle of another.

Where a module can directly access,change or modify or refer to the content of another module.