1. Assistanship Assistant : Denny, TE 2002
Type : not compulsary, only when necessary
Duration : once a week, not more than hours.
Time,place : ask assistant
Registration : send to:

2. Web address for course material

3. Modularisation
Lecture 8

4. Motivation
Complexity of programming problem  more difficult to consider the solution as a whole  clue: dividing the problem into small parts (module)
Each module represent single task, free of error
Modularisation : is the process of dividing a problem into separate tasks, each with a single purpose.

5. Benefits of modular design
Ease of understandingeach module has only one function
Reusable code
Elimination of redundancy  avoid the repetition of writing
Efficiency of maintenance

6. Modular name convention
Describe the work to be done as a single specific function
Use a verb, followed by a two-word object.
Example:
Print_page_heading
Calculate_sales_tax
Validate_input_date

7. Example 8.1
Design a solution algorithm that will prompt a terminal operator for three characters, accept those characters as input, sort them into ascending sequence and output them to the screen. The algorithm is to continue to read characters until ´XXX´is entered.

8. Defining diagram Input Processing Output Char_1 Char_2 Char_3
Prompt for characters
Accept three characters
Sort three characters
Ouput three characters

9. Original Solution algorithm
Process_three_characters
Prompt the operator for char_1, char_2, char_3
Get char_1, char_2, char_3
DOWHILE NOT (char_1=´X`AND char_2=´X´AND char_3=´X´)
IF char_1>char_2 THEN
temp = char_1
char_1 = char_2
char_2 = temp
ENDIF
IF char_2>char_3 THEN
temp = char_2
char_2 = char_3
char_3 = temp
Output to the screen char_1, char_2, char_3
Prompt operator for char_1, char_2, char_3
ENDDO
END

10. Solution Algorithm using a module
Process_three_characters
Prompt the operator for char_1,char_2,char_3
Get char_1, char_2, char_3
DOWHILE NOT (char_1=´X`AND char_2=´X´AND char_3=´X´)
Sort_three_characters
Output to the screen char_1,char_2,char_3
Prompt operator for char_1, char_2, char_3
Get char_1,char_2,char_3
ENDDO
END
IF char_1>char_2 THEN
temp = char_1
char_1 = char_2
char_2 = temp
ENDIF
IF char_2>char_3 THEN
temp = char_2
char_2 = char_3
char_3 = temp
´Controlling module´or
´Calling module´or
´Mainline“
`Subordinate module` or `Called
Module`

11. Hierarchy charts or structure charts or visual table of content
President
Vice_president
Sales
Vice_president
Finance
Vice_president
Personnel
Manager A
Manager B
Manager C
Manager D
Manager E
Manager F

12. Hierarchy Chart Example 8.1
Process_three_
characters
Calling module
Sort_three_
characters
Called module

13. Example 8.2 Process three characters
Design a solution algorithm that will prompt a terminal operator for three characters, accept those characters as input, sort them into ascending sequence and output them to the screen. The algorithm is to continue to read characters until ´XXX´is entered.

14. Defining diagram Input Processing Output Char_1 Char_2 Char_3
Prompt for characters
Accept three characters
Sort three characters
Ouput three characters

15. Solution Algorithm Mainline 1rst Module 2nd Module 3rd Module
Process_three_characters
Read_three_characters
DOWHILE NOT (char_1=´X`AND char_2=´X´AND char_3=´X´)
Sort_three_characters
Print_three_characters
ENDDO
END
Prompt the operator for char_1,char_2,char_3
Get char_1, char_2, char_3
IF char_1>char_2 THEN
temp = char_1
char_1 = char_2
char_2 = temp
ENDIF
IF char_2>char_3 THEN
temp = char_2
char_2 = char_3
char_3 = temp
Output to the screen char_1, char_2, char_3
Mainline
1rst Module
2nd Module
3rd Module

16. Hierarchy charts Process_three_ characters Read_three_ characters
Sort_three_
characters
Print_three_
characters