Function Oriented Design

Function Oriented models show how the incoming data combined with the stored and static data can be transformed to the output data which is required by the system. This transformation is performed by a set of functions. 

In late 1960, there was the rapid development of hardware and ad-hoc software development. Because of that many problems start to come up when software development. difficult to design, difficult to write and test, virtually impossible to understand and also difficult to maintain, also no corresponding development for methodologies for software development. with those disadvantages, software development fell into the crisis. as a solution this crisis start to develop programming methods using some designs. we are going to talk about those three methods.

                                        Structure Charts

                                        N-S charts 

                                        Data Flow Diagram

Structured Programming 

Using some structuring method to carry out program design and other steps. Using this methodology order provide us verification of algorithm correction to ensure program reliability, systemic program process, relating the programming task to the program design structure. when we test modular programs basically we use standard control constructs. 

1. sequence structure

2. Selection structure

3. Repetition structure

                                            

Module Programming

usually, module programs are hierarchically ordered. When using a module structures program there is always some rule that must follow. 

     only one unique entry point and exit point.

     it is a self-contained structure.

     At one time it will perform one logical task only.

     use of control constructs.

N-S Chart (Nassi-Shneiderman Diagram)

NS chart also is a graphical design representation for structured programming. This diagram was designed in 1972 by Isaac Nassi and Ben Shneiderman who were both graduates of Stony Brook University.

Data Flow Diagram (DFD)

DFD is known as traditional charts that represent the information flows within the system. just like other structure charts also these charts show how data enter and leaves the system. also these charts represent what change the information and where data is stored.

When we design the DFD we use some symbols to represent the process steps. also, there are some points must keep remembering when we designed a DFD.

Data can not flow between two entities directly.

Data can not flow between two data stores directly.

A process must have at least one input data flow and one output data flow.