a) Defenition of Hierarchy Diagram:
The Hierarchy Diagram begins at the Top Level with the Main Module. The Main Module represents a program's main routine and is the highest module that controls the overall logic of the program. The other modules in the Hierarchy Diagram may be considered as SubModules of the controlling or Main Module and they are performed when the Main Module "CALLs or PERFORMs" them and they then return control to the Main Module when their logic is complete.
That is, the Main Module is the starting point of the logic and it CALLs Sub Module 1 for logical service (The Main Module notes the Return Point in its own logic and goes to a Wait State until Sub Module 1 has completed it's function).
When Sub Module 1 has completed its task, it issues a RETURN and the logic returns to the Return Point maintained by the Main Module's logic. The Main Module then continues by CALLing Sub Module 2 in the same manner. Note that Sub Module 2 RETURNS control to the Main Module and that the logic terminates in the Main Module (NOT Sub Module 2). Each of the SubModules may in turn be composed of lower level SubModules and they in turn CALL or PERFORM SubModules in the same controlling manner as the Main Module CALLed them. This then can go on recursively until the required logic is implemented and each major processing function is reduced to a series of logically (functionally) independent subfunctions.
|Consequently each Module accomplishes a specific logical task, and together, the Modules solve the logical need of the Main Module (or program). A Hierarchy Diagram is developed in a manner similar to the procedures used to develop an outline of a report or paper.|
Note: The outline should be developed before detailing the report and so a Hierarchy Diagram should come before the program code. The Hierarchy Diagram is not a complete description of the logic of a program since it only shows "What?" are the tasks and NOT "How?" the tasks do their job.
Hierarchy Diagram for Students Registration System.
|b) Defenition of a class:|
In Object oriented programming,a category of objects is called a class. The class defines all the common properties of the different objects that belong to it.
Complete details of classes:
|Description of the classes:|
Here , this system attempts to furnish details to the students about the courses available in the institution in order to aid the students to choose their option.However the students details are collected,before a student is admitted.
There is a process called “Admission”,which takes care of the checks to be made on validity of the information provided by the students and then to see if they qualify to enter into the course they have opted for.If the conditions are satisfied, the student is taken into the institution and the batch convenient or priorly fixed is conveyed to them.
The Hierarchy diagram ,attempts to give a clear idea of WHAT is happening in the Student registration process. And the classes are explained to the last detail.