1. Top-Down Design & JSP Skill Area Part D
Materials Prepared by Dhimas Ruswanto, BMm

2. Lecture Overview Top-Down Design Modular Development JSP
Program Documentation

3. Top-down design

4. Big Problems
It is easier to solve small problems than it is to solve big ones
It’s hard to solve big problems
Computer programmers use a divide and conquer approach to problem solving:
a problem is broken into parts
those parts are solved individually
the smaller solutions are assembled into a big solution
These techniques are known as top-down design and modular development.

5. Top-down Design
Top-down design is the process of designing a solution to a problem by systematically breaking a problem into smaller, more manageable parts.

6. Top-down Design
First, start with a clear statement of the problem or concept – a single big idea.

7. Top-down Design
Next, break it down into several parts.

8. Top-down Design Next, break it down into several parts.
If any of those parts can be further broken down, then the process continues…

9. Top-down Design Next, break it down into several parts.
If any of those parts can be further broken down, then the process continues…
…and so on

10. Top-down Design
The final design might look something like this organizational chart, showing the overall structure of separate units that form a single complex entity.

11. Top-down Design
An organizational chart is like an upside down tree, with nodes representing each process.

12. Top-down Design
An organizational chart is like an upside down tree, with nodes representing each process.
The leaf nodes are those at the end of each branch of the tree.

13. Top-down Design
The leaf nodes represent modules that need to be developed and then recombined to create the overall solution to the original problem.
Top-down design leads to modular development.

14. Modular Development
Modular development is the process of developing software modules individually…

15. Modular Development
Modular development is the process of developing software modules individually…
…then combining the modules to form a solution to an overall problem.

16. Modular Development Advantages
Modular development of computer software:
makes a large project more manageable
is faster for large projects
leads to a higher quality product
makes it easier to find and correct errors
increases the reusability of solutions

17. Modular Development Advantages
… makes a large project more manageable.
Smaller and less complex tasks are easier to understand than larger ones and are less demanding of resources.

18. Modular Development Advantages
… is faster for large projects.
Different people can work on different modules, and then put their work together. This means that different modules can be developed at the same time, which speeds up the overall project.

19. Modular Development Advantages
…leads to a higher quality product.
Programmers with knowledge and skills in a specific area, such as graphics, accounting, or data communications, can be assigned to the parts of the project that require those skills.

20. Modular Development Advantages
…makes it easier to find and correct errors.
Often, the hardest part of correcting an error in computer software is finding out exactly what is causing the error. Modular development makes it easier to isolate the part of the software that is causing trouble.

21. Modular Development Advantages
… increases the reusability of solutions.
Solutions to smaller problems are more likely to be useful elsewhere than solutions to bigger problems.
They are more likely to be reusable code.

22. Jackson Structured Programming

23. Jackson Structure Diagram
Another Top-down design leads is Jackson Structure Diagram
The Jackson Structure Diagram is a notation used in JSP (Jackson Structured Programming),

24. Jackson Structured Programming
JSP was developed in the 1970’s by Michael Jackson.
A JSP is used to explain the inner workings of a program.
There are three types of “box” notations used to represent the workings of a program:

25. JSP Sequence

26. JSP Sequence (Examples)

27. JSP Selection

28. JSP Selection (Examples)

29. JSP Selection (Examples)

30. JSP Iteration

31. JSP Iteration (Examples)

32. Program Documentation

33. Program Documentation
Why is program documentation important?
To describe the design of you program.
To tell other programmers what the program does and how it works
Can help programmer who is making the modifications understand another programmer’s code

34. Essential Elements of Program Documentation
For an individual module:
Who has written the module
When the module was written or modified
Why the module was written or modified
How the module interacts with other modules
What special algorithms were used
Acknowledge outside sources for ideas and algorithms

35. Essential Elements of Program Documentation
For data structures:
What data structure is used
Why a particular structure was used
What data is contained in the structure
How the data structure is implemented

36. SUMMARY
Top-down design is the process of designing a solution to a problem by systematically breaking a problem into smaller, more manageable parts.
Modular development is the process of developing software modules individually then combining the modules to form a solution to an overall problem.
A JSP is used to explain the inner workings of a program.
Why is program documentation important?
To describe the design of you program.
To tell other programmers what the program does and how it works
Can help programmer who is making the modifications understand another programmer’s code