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Analysis and Design
Structure of Modules
We have discussed in the previous chapter Functional
Modeling - Part I that a system may be seen as a combination of everal small
independent units. So, while designing software also, it is designed as a collection
of separately named and addressable components called modules.
This property of software is termed as modularity. Modularity is a very important
feature of any software and allows a program to be intellectually manageable.
For instance, while coding small programs in 'C' also, we make a program as a
collection of small functions.
A program for finding average of three numbers may make use of a function for
calculating the sum of the numbers. Each of these can be called as a separate
module and may be written by a different programmer. But once such modules are
created, different programs may use them. Thus modularity in software provides
several advantages apart from making the program more manageable.
While designing the modular structure of the program, several issues are to
be paid ention. The modular structure should reflect the structure of the problem.
It should have the following properties.
1. Intra-module property: Cohesion
Modules should be cohesive.
2. Inter module property: Coupling
Modules should be as loosely interconnected as possible.
- Highly coupled modules are strongly interconnected.
- Loosely coupled modules are weakly connected.
- De-coupled modules exhibit no interconnection.
3. A module should capture in it strongly related elements of the problem.
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