Payback Period and Modularisation

What is Payback Period?

The time period a system takes to generate enough saving to cover development cost is known as payback period.


The process of breaking down a problem into smaller peaces(called modules) is known as modularisation. It helps us focus on a particular peace of problem without worring about the overoll problem. It also helps the developer to wright more structured and better solutions that are easy to work with and more readable.


Modules make the system not only simple and easier to understand but also easier to redesign and rebuilt. A module is represented by a box with a module name in it.


Connections between modules are represented using links between mosules. Connectors connect any two modules with the arrows drone in down ward direction.


It refers to the strength of relationship between modules in a system. It can be of two types 1- Data Couple, 2- Control Couple.

Data couple carrys data and it can have upward and downward direction. Data flows are depicated using named arrows with a small circle at one end. But control couple only carrys infromation about data couple and does not carry any data. It is always directed upwards because it show’s the module which is to be invoked control flows are depicted using named arrows with a small filled circle at one end.


It is used to denote the intra-moduler strength. It is a relationship among eliments within a module. A system designer should aim at minimising coupling and maximising cohesion to get a moduler design.

A good design is carectorized by-

  • Low coupling that is low inter dependence among module.
  • High cohesion that is high inter relationship between the elements within a single module.