Int 2 Computing

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Int 2 Computing

• Software Development
• The Software Development Process

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The Software Development Process (SDP)

• To be a successful programmer takes a logical and
  reasoned approach to problem solving.
• Good practice is the result of a series of
  well-documented stages.
• Each stage makes an important contribution to the
  whole development process.

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The Seven Stages

• Analysis.
• Design.
• Implementation.
• Testing.
• Documentation.
• Evaluation.
• Maintenance.

Some stages may have to be repeated if the
software does not meet the requirements. This
mean that the process can be described as an
iterative process.
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Analysis

• This stage extracts information from the client
  and other relevant staff.
• This may take many forms
• Interviews with clients and staff.
• Observation of current system.
• Examination of current paperwork.
• It is important that the task is fully agreed
  before the design stage can begin as the
  Specification is a legal Contract.

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Design

• The design may be either a
• Pseudocode A design written in a code like
  version of English. Each line of design should
  relate to one line of code.
• Or
• Structured Diagram A graphical design that can
  describe the overall structure of the proposed
  program

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Pseudocode - Example

• 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
Simple English words in a familiar program form
Notice the numbering system
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Structure Diagram an example
A structure diagram allows the design of a
program to be drawn out in diagrammatic form.
Here is an example
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Implementation

• This stage involves coding the algorithm in a
  chosen language. To chose a language we must
  consider.
• Type of problem.
• Hardware and software compatibility.
• Datatypes available.
• Features and Constructs available.

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Testing

• To ensure that the implementation is correct the
  testing should be systematic and comprehensive.
  This is normally carried out by an Independent
  Test Group (ITG).
• Comprehensive testing should include
• Normal data Data within the expected range.
• Extreme data (Boundary data) Data at the edge of
  the expected range.
• Exceptional Data (Out of range data) Data
  outside the expected range.

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Documentation

• The programmer must also create several documents
  including
• Structured Listing A formatted printout of the
  actual code.
• Test Report A list of test data with predicted
  and actual output.
• User Guide A set of instructions on how to
  install and use the software.
• Technical Guide Descriptions of any technical
  requirements. It may also record the development
  history of previous versions.

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Evaluation

• A report is produced and given to the client that
  will state whether the software is fit for
  purpose.
• If software is to be considered fit for purpose
  then it must be able to meet all the criteria in
  the software requirements document.

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Evaluation (Cont.)

• The software should also be evaluated in terms
  of
• Robustness The ability to cope with errors when
  running. E.g.Not crashing.
• Reliability The ability to cope with expected
  data and give correct and predictable results.
• Portability The ability to run on a computer
  system other than the one the software was
  designed for. E.g. Run on both a PC and a Mac.

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Evaluation (Cont.)

• Efficiency Not using too much of the Computers
  memory or processor time.
• Maintainability The ability to be changed with
  ease in the future. E.g.
• Readability. Using meaningful variable names and
  sensible comments throughout the program.
• Modularity. Using Procedures, functions or
  Subroutines.
• Documented History. Are previous versions of the
  software documented.

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Maintenance

• Starts when the software is handed over to the
  client.
• The three types of maintenance are
• Corrective Fixing errors not found during
  testing.
• Adaptive Changing the code to cope with changes
  made to the environment.
• Perfective Adding new features or amendments
  requested by the client. This is beyond the
  original specification and will cost the client
  extra.

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Personnel

• Client The client commissions the software,
  describing the scope and boundaries of the
  problem to the analyst.
• Systems Analyst The systems analyst agrees with
  the client the detailed specification of the
  software to be written. This should be completed
  to the satisfaction of both parties before the
  design or coding is carried out.

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Personnel (Cont.)

• Project manager This individual takes sole
  responsibility for keeping the project on track,
  from the receipt of the software specification
  until the software is delivered to the client.
• Programmer The programmer is responsible,
  individually or as part of a team, for converting
  the algorithm into program code.

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Personnel (Cont.)

• Independent test group The independent test
  group (ITG) carries out testing of the software.
  This may be modular testing and/or component
  testing, looking at important subsections of the
  code. It will also entail testing of the finished
  product.