1. The Software Development Process
Analysis
Design
Implementation
Testing
Documentation
Evaluation
Maintenance

2. Fact Finding
Analysis is a fact-finding process, and there are five key questions that need to be asked, often repeatedly.
These key questions are:
WHO?
WHAT?
WHERE?
WHEN?
WHY?

3. An Iterative process
It is important to realise that the software development process is iterative in nature. This means that the problem will be revisited a number of times getting closer and closer to the required solution on each time round.

4. Systems Analysis What is a systems analyst?
A systems analyst observes, clarifies and models an existing system to assess its suitability for computerisation. In the process, the analyst could also find ways of improving the system.
The systems analyst must have a sound technical background. They may once have been programmers.

5. Skills and techniques of the Systems Analyst
The systems analyst must
extract the clients needs
document these needs in a formal way
communicate these to the designers

6. Extracting the Clients Needs
Extracting the clients needs is known as requirements elicitation.
This is done by:
interviewing the client’s management personnel
making observation notes of the client’s business
The analyst will also inspect information sources used by the client to keep track of their business.

7. The Requirements Specification
is the end result of the requirements elicitation
is a written statement of what the design team must go on to make
It is extremely important to get this document right. Mistakes made later can be very costly.

8. Documentation (analysis stage)
The systems analyst must document the clients needs by drafting formal reports:
requirements specification
system specification

9. Design Representations
There are a number of commonly used forms of design representation in common use.
Examples include:
structure diagrams
pseudocode

10. Structure Diagram
A commonly used syntax for structure diagrams is as follows:
A procedure
A loop
A decision
A single task

11. An example:
A structure diagram allows the design of a program to be drawn out in diagrammatic form. Here is an example:

12. Pseudocode
Pseudocode is another example of a method of describing a program.
Simple English words are used to describe the steps of the algorithm and any refinements made.

13. Pseudocode - Example Top level design Simple English
1. Display information
2. Get details
3. Do calculation
4. Display answer
Refine step 2
2.1 display prompt
2.2 get value
2.3 while value out of range
2.4 display error message
2.5 get value
2.6 loop
Top level design
Simple English
words in a familiar
program form
Notice the numbering system

14. Designing the Solution
Once the needs of the user are clearly understood and documented, software development can move onto the next stage, involving the DESIGN of the system.
Design of the User Interface
Design of the structure of the software
Design of the detailed logic of the software

15. Implementation
The next stage involves turning the carefully structured design into a working solution.

16. Choosing an Environment
Before we can implement a solution we must decide on the programming environment which is most suitable.
Languages are generally designed for a specific purpose.

17. Programming Languages

18. Things to Remember...
The code should be modular, - procedures and functions should be used. Library modules should be ‘closed’ so that the variables used in them cannot disturb the code of the rest of the program.
Meaningful variable names should be used.
There should be internal commentary, explaining what each section of the code does. Where a complex algorithm has been implemented, it is helpful to comment on several lines of the code, in addition to a general description of what the module does.

19. Things to Remember (2)
Where parameters are being used in a module, they should be described in the commentary of the module. This is particularly important in library modules.
Parameter lists should be small and manageable. If a procedure or function requires a set of parameters which is very big, then it is likely that it is performing more than one program function. The original design needs to be revisited, and functionally decomposed.

20. Debugging the Solution
A common technique in trying to debug a piece of software is to conduct a structured walkthrough (step through each line of logic in the code) using a structured listing,
which is simply a formatted display or printout of the code. It is important that the code is written in such a way that helps the above activities.

21. Dry Runs
To complete a dry run the programmer works through a section of program code by hand. This is very useful for locating errors in both syntax and semantics.
A trace table will normally be used in this activity.

22. Trace Tables
A trace table is constructed with a column to identify the instruction executed and a column for each variable.
The programmer works through each line of the listing changing the appropriate variables.

23. Test Data
The expected results from a test data set must be known in advance, so that they can be checked against the actual results. You should include test data to demonstrate the following:
1. “normal” operation of the software, to make sure that there are no unexpected results in ordinary work.
2. the operation limits of the software, to make sure that the boundary conditions identified in the design stage are being handled properly.
3. “exceptions” to the normal operating conditions. This set will show whether or not the software can react to unexpected inputs in an effective way, without crashing.

24. Documentation - The User Guide
This document should describe how to use the software.
Ideally there should also be tutorial files which can take the user through examples of a piece of work, and allow them to become familiar with the commands, and the various sections of the software.

25. Documentation - The Technical Guide
This document should provide information on
how to install the software
hardware requirements
software requirements

26. Evaluation Does the solution meet the user requirements?
Judge this against a set of criteria
screen layout
help required
user prompts
fitness for purpose
maintainability
robustness
reliability
portability

27. Some Definitions (1) Correctness Maintainability
A program is correct if it matches the users requirements
Maintainability
A program will be easily maintained if it has been written in a way which will make it easy to change. This will include
internal commentary
meaningful variable and procedure names
parameter passing

28. Some Definitions (2) Reliability Readability
A program is reliable if it is free from bugs, ie it must meet the requirements repeatedly under severe testing
Readability
A program is readable if it is easily understandable by people other than the original programmer, ie good internal documentation, use of white space, etc.

29. Some Definitions (3) Portability Efficiency
A program is said to be portable if it can be transferred from one system to another with minimal adaptation
Efficiency
A program is efficient if it uses the most appropriate structures for the job. It should run as fast as possible and not use up more system resources than are necessary.

30. Some Definitions (4) Robustness Fitness for Purpose
A program is said to be robust if it does not crash when invalid data is input or unexpected results are generated.
Fitness for Purpose
Does the program meet the requirements?

31. Maintenance Activities identified as part of maintenance:
corrective (17%)
adaptive (18%)
Perfective (65%)

32. Maintenance Costs
Maintenance is very costly. It is vital that errors are detected at as early a stage as possible.