Coupling Classification

System coupling originates from physics. In physics, coupling refers to a measure of the mutual dependence of two entities on each other. It is divided into the following categories:

indirect coupling

There is no direct relationship between the two modules, and the connection between them is completely realized through the control and invocation of the main module.

data coupling

When one module accesses another, it exchanges input and output information with each other through simple data parameters (not control parameters, public data structures, or external variables).

tag coupling

A set of modules passes record information through a parameter list. This record is a substructure of a data structure, not a simple variable.

control coupling

Control coupling occurs when a module explicitly controls the function of selecting another module by transmitting control information such as switches, logos, names, etc.

external coupling

When a group of modules all access the same global simple variable instead of the same global data structure, and do not pass the information of the global variable through the parameter table, it is called external coupling.

public coupling

If a group of modules all access the same common data environment, the coupling between them is called public coupling. The common data environment can be the communication area shared by the global data structure, the common coverage area of the memory, etc.

content coupling

Content coupling occurs between two modules if:

①A module directly accesses the internal data of another module;

②A module is not transferred to the inside of another module through the normal entrance;

③ Some of the program codes of the two modules overlap (may only appear in assembly language);

④ A module has multiple entries.