Benefits and Principles of Modular Programming

Modularity

A well-defined segmentation of the project effort ensures system modularity. Each task forms a separate, distinct program module. At implementation time each module and its inputs and outputs are well-defined, there is no confusion in the intended interface with other system modules. At checkout time the integrity of the module is tested independently; there are few scheduling problems in synchronizing the completion of several tasks before checkout can begin. Finally, the system is maintained in modular fashion; system errors and deficiencies can be traced to specific system modules, thus limiting the scope of detailed error searching.

The benefits expected of modular programming are: (1) managerial–development time should be shortened because separate groups would work on each module with little need for communication: (2) product flexibility-it should be possible to make drastic changes to one module without a need to change others; (3) comprehensibility-it should be possible to study the system one module at a time. The whole system can therefore be better designed because it is better understood.

In some context “module” is considered to be a responsibility assignment rather than a subprogram. The modularizations include the design decisions which must be made before the work on independent modules can begin. Quite different decisions are included for each alternative, but in all cases the intention is to describe all “system level” decisions (i.e. decisions which affect more than one module)

Information hiding

The purpose of information hiding is to obtain a modularization of the code of a system that isolates changes into single modules.

References

On the Criteria To Be Used in Decomposing Systems into Modules [D.L. Parnas]