Maintaining code topic for SDD

1. Mo!fying So"ware Solutions
A topic in an hour

2. Please write the following comments on your syllabus
Algorithms Explicit
integrate Reverse
Changing engineer
System Meaningful
Standards Comments
Data Indentation
Outsource

3. Why did we write them
down?
Whe’re playing

4. Reasons for Maintenance Co!ng
Changing user requirements
Eg, Microsoft Word...people want to add pictures,
graphs, charts, integrate excel spreadsheets,
essentially...desktop publish
Even clip art

5. Changing user requirements

6. Upgrading the user interface

7. Changes in the data to be processed
Format from one system can be often need to be
implemented into another system.
If this data changes, you may need to change the
new system.

8. Introduction of new hardware or soft ware
Introduction of new peripherals. Eg, scanners need
scanner drivers, printers need printer drivers
USB Drives a major introduction in the past 4
years.
Introduction of new standards of saving files
Sometimes, just to be competitive

9. Changing organisational focus
A company creates an program where they hire
book-keepers to do their books
OR
A company that decides to outsource their book-
keeping and only needs to enter sales/expenses

10. Changes in government
requirements

11. Poorly implemented code

12. Social and ethical Implications
Plaigarism
You can’t reverse engineer code
You must reference any code that you use
Open source restrictions

13. Features in source code that improve it’s
maintainability
Use of variables instead of values.
Radius=3
Circumference = 2 * Pi * Radius
instead of
Circumference =2 * Pi * 3

14. Features in source code that improve it’s
maintainability
Meaningful Variable Names
Bob=3
c1 = 2 * Stuff * Bob
instead of
Circumference =2 * Pi * Radius

15. Features in source code that improve it’s
maintainability
Explaination comments in code
Circumference =2 * Pi *
Radius //radius is the distance
from the centre to one edge,
input by the user in a text box.
Declared on form 1

16. Features in source code that improve it’s
maintainability
Use of Standard Control Structures
For (i= 1 to 10)
Bob = i + 1;
Next i
OR
Bob =i + 1
Go to line 10 until i =10

17. Features in source code that improve it’s
maintainability
A clear and uncluttered program
Use of indentation!
/*Simple HelloButton()method
version 1.0 author JohnDoe*/
HelloButton(){JButton hello=new
JButton (“Hello
World”);hello.addActionListener(
new HellowBtnList) JFrame
frame=newFrame(“Hello Button”);
Container pane =
frame.getContentPane();
pane.add(hello);

19. Features in source code that improve it’s
maintainability
One logical task per subroutine!
This means that subroutines can be reused for
different things within other programs and also
If say, data changes, you don’t have to get rid of
every process, only those that have to do with
saving in that format.

20. Interpretation
Documentation of the process, and product should
be availiable for developers to interpret code.
Documentation can be:
Internal or External
External can be based around:
Development : for developers by developers
Use: for users by developers

21. Algorithms (and IPO) are the best things to look
back to to be able to understand and modify code
Sometimes, when algorithms are not stored they
need to be rewritten to understand:
Inputs
Types of Variables
Processes
Outputs

22. Use supplied documentation to
Identify how control structures have been used
Explain how variables have been used.
Documentation:
The following is a piece of code supplied to you.
You need to:
Convert the code to an algorithm

23. code
For J=0 to Last
ThisChar=textEntry.Text.Chars(J)
If IsLetter(ThisChar) or ThisChar “ ‘ “
If Not InAWord Then
WordCount +=1
End If
InAWord=True
Else
InAWord=False
End If
Next J

24. What was all this about again?
Coding so that it is easier for people to modify,
making your code explicit
Being able to modify other people’s code