Announcements:

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Announcements

• The blackboard vista (e-learning) site is
  available via goWMU
• I will be changing my office hours. The new
  office hours are as follows
• Wednesday 115-315 PM, Thursday 11-noon
• All assignment submissions must run using Visual
  Studio 2008
• Did someone leave their sunglasses last class?
  (If so, I might have them)
• Is someone in this class typing their lecture
  notes? If so, please see me after class - thanks!

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CS1120 C Review

• Will be this Friday (9/05/08) from noon-2 PM in
  C-224 (same as lecture)

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CS1120 Computer Science II

• Software Life Cycle

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What exactly is software?

• Possible definitions of software are
• Instructions (i.e., computer programs) executed
  to provide features, functions, and performance
• Data structures that enable the programs to
  adequately manipulate information
• Documents that describe the operation and use of
  programs

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Categories of Software

• System Software
• Compilers, editors, file management utilities
• Application Software
• Standalone programs to solve a specific need
• Engineering/Scientific Software
• Computer-aided design, simulation
• Web-applications

• Embedded Software
• Resides inside another product or system
• Product-line Software
• Inventory control, financial applications
• Artificial Intelligence Software
• Neural networks, pattern recognition, robotics,
  game playing

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What is Software Engineering?

• This is the study and use of engineering
  principles to create software that is both
  reliable and efficient on real computers

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Software Quality

• Software engineering is the production of quality
  software
• External quality
• May be detected by its users
• Internal quality
• Perceptible only to computer professionals who
  have access to the actual software text
• What matters is the external quality, but it can
  only be achieved through internal quality

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External Quality

• Correctness
• Perform the exact tasks as specified
• Robustness
• Ability to react appropriately to abnormal
  conditions
• Extendibility
• Ease of adapting program to changes of
  specification
• Reusability
• Ability of software elements to serve for the
  construction of many different applications.

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External Quality

• Other Quality
• Compatibility, Portability, Ease of Use,
  Efficiency, Timeliness, Integrity
• Tradeoffs
• Integrity v.s. Ease of Use
• Efficiency v.s. Portability
• Timeliness v.s. Extendibility

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The Waterfall Model

• This is the classic life cycle
• One of the oldest models in software engineering
• A sequential and systematic approach to software
  development
• Communication --gt Planning --gt Modeling --gt
  Construction --gt Deployment

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Software Life Cycle

• This is a more realistic look at software - as a
  continuous process

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Software Life CyclePhase 1 Specification

• Answers What do we build?
• Define clearly all aspects of the problem
• What is input (valid/invalid) data?
• What assumptions are possible?
• Are there special cases?
• What enhancements are likely in the future?

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Software Life CyclePhase 2 Design

• Divide into manageable parts - modules
• Specify each modules purpose, assumptions,
  input, and output
• Develop algorithms
• Look for existing software components

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Software Life CyclePhase 3 Risk Analysis

• Attempts to answer What can go wrong, and how
  bad can it be?
• Predict and manage what risks you can
• Risks to timetable, cost, human health, etc.
  should be taken into account
• Risks can greatly influence the direction of a
  project

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Software Life CyclePhase 4 Verification

• Answers Are the algorithms correct?
• Some algorithms can be proven correct
• assertion condition at a certain point
• invariant condition that is always true

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Software Life CyclePhase 5 Coding

• Translate the algorithms into a particular
  programming language
• Minor phase in the software life cycle

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Software Life CyclePhase 6 Testing

• Answers Did we build it correctly?
• Try to make the software fail
• Develop as many test cases as possible
• Both a science and an art

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Software Life CyclePhase 7 Refining a Solution

• Add bells and whistles
• Retest after any changes are made

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Software Life CyclePhase 8 Production

• Distribute it
• Install it

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Software Life CyclePhase 9 Maintenance

• Fix previously undiscovered bugs
• Add new features
• Enhance old features
• Generally the most costly phase (80 of total
  cost by some estimates)

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Software Life CycleDocumentation

• Performed extensively in every phase
• In modern software development, there are
  typically different people working on each phase
  of the software life cycle
• Novice programmers usually undervalue
  documentation

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Continuing Effort
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More Models

• There are many models of software development
• Incremental Process Models
• Incremental, RAD (Rapid Application Development)
• Evolutionary Process Models
• Prototyping, Spiral, Concurrent Development
• Specialized Process Models
• Component-Based, Formal Methods, Aspect-Oriented

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The IN Method

• Agile Development
• This software engineering methodology focuses on
  customer satisfaction, incrementally developing
  software using small teams, using simplicity of
  development, and heavy communication with
  customers
• There are many flavors including
• Extreme Programming (XP), Adaptive Software
  Development (ASD), Dynamic Systems Development
  Method (DSDM), Scrum, Crystal, Feature Driven
  Development (FDD), and Agile Modeling (AM)