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CS 111 – Nov. 22

CS 111 – Nov. 22. Chapter 7 Software engineering Systems analysis Commitment Please read Section 7.4 (only pp. 336-341), Sections 7.6-7.9 Homework #2 due Nov. 29. Software engineering. Large software systems cannot be written by 1 person Several people work together

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CS 111 – Nov. 22

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  1. CS 111 – Nov. 22 Chapter 7 • Software engineering • Systems analysis • Commitment • Please read Section 7.4 (only pp. 336-341), Sections 7.6-7.9 • Homework #2 due Nov. 29

  2. Software engineering • Large software systems cannot be written by 1 person • Several people work together • Each is responsible for portion of program • These portions interact… so must make sure your piece will fit correctly in jigsaw puzzle • Example: developing user interface for registration system: Your output (list of desired course sections) must be in format expected by next phase of program • Deadlines

  3. Tips for success • General guidelines • Don’t reinvent the wheel • Make your solution efficient, elegant, easy to understand • Build solution incrementally, test & document often • It’s easier to fix a bug the sooner it’s found! • Work in pairs, check each other’s work • Integrated development environment (IDE) • Software that simplifies job of writing code • As you type, “code” becomes color coded • Automates compiling and testing • Built-in debugger: can trace through instructions one by one, inspecting values of variables: rather than modifying code by inserting print statements!

  4. Software life cycle • Very similar to problem solving procedure • Problem specification written • Design of solution • Implementation • Testing • Maintenance

  5. Systems analysis • Distinction… • Software engineering is mainly concerned with implementation of the project • Systems analysis is mainly concerned with specification and design • Definition of systems analysis (Whitten & Bentley): • “A systems analyst facilitates the study of the problems and needs of a business to determine how the business system and IT can best solve the problems and accomplish improvements for the business.” • The finished product is eventually a new or improved computer application, implemented by software engineers.

  6. Principles • Get the owners and users involved • The program you’re designing doesn’t belong to you. It’s to help other people. Find out what they desire. • Follow problem solving procedure • Define what a suitable solution must accomplish / do. • Evaluate possible algorithms, and choose the best • After testing, evaluate new system’s impact, get feedback from stakeholders. • Establish a schedule for the software life cycle • How much time do you have • How many people can you have on your team & for how long? • What are their strengths and weaknesses?

  7. Principles (2) • Establish coding and documentation standards • Your software engineers are writing code for you. Almost like they are students in your class. • Essential to have code written in a consistent style • Encourage good documentation communication, including list of known problems. Let your people know they won’t be penalized for admitting their work is incomplete. You don’t want these to be a secret, or else risk future debugging. • Give people a list of deadlines of deliverables. • Have your team members meet with you to discuss their accomplishments. • Is the project work cost-effective? • May need to scale down, trim some functionality or put off to later version.

  8. Principles (3) • Beware the “mythical man-month” • Doubling your staff will not make project take half the time. IBM found this out the hard way in its System/360 project. • Diminishing returns • Don’t be afraid to scale down or cancel project • Project should have milestones / checkpoints to evaluate path toward success • Decide how to get back on track, or reduce scope of project. • Can final deadline be extended? • If doomed, abort project and cut losses. • But, will your superiors understand?

  9. Principles (4) • Divide and conquer • A large project can be overwhelming at first. Break into small, manageable parts. • Reminds me of studying for a final exam, or writing large essay. • Top-down design and bottom-up implementation. • Design for future growth and change • Your project may be in service for 10+ years • People who adopt and like your work may want to continue using it forever. • You will have to live with decisions you make today. (For example, choice of programming language)

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