Software Engineering

1. Software Engineering CSC 180 Lecture 10 Dr. Adam Anthony

2. A VERY Brief Overview CSC 180 Part I CSC 180 Part II • Where big software comes from (today’s lecture) • Operating Systems • Web Applications • Networking • Selected Topics • The softer side of computing • How computers work • Bits and Bytes • Math • Algorithms • Hardcore Computer Science

3. Overview • Software Engineering Discipline • Software Life Cycle • Development Methodologies • Structuring Projects • Basic design diagrams • Testing • Documentation • Ethical Concerns • Jobs/Majors that support the software life cycle

4. What is Software Engineering? • First, what is traditional engineering? • Skilled, specialized development and management of a large physical project (automobile, skyscraper, power plant) • Software engineering is the same thing, but for programming projects instead of physical systems • Except: • Fewer standardized components • Hard to define measures (metrics) of success • Costs are intangible • Quality is hard to assess

5. The Software Life Cycle • Development: software created here • Use: software distributed to users, bugs revealed • Maintenance: • Fix bugs • Add improvements • Compared to physical systems: • maintenance typically involves repairs, not improvements • Maintenance of software takes longer, costs more

6. The Development Phase

7. Development: Requirements Specification • Specify what services the system will provide • Identify any special conditions (security, speed, availability) on those services • Define how the outside world will interact with the system • Always keep the customer in mind • They are the ones who buy/use it! • Companies frequently hire systems analysts for this type of work • Need to be a ‘people person’ who also has strong technical knowledge

8. Use-Case Diagrams • Inside box: • Interactions: features of the software that the user will see/use • Outside box: • Stick figures that represent actors: • People • Other comptuers • Special Devices

9. Your Turn! • Teams of 3-4: • Brainstorm a use-case diagram for a smart phone application • May be an application that already exists, or something made up • Factors to consider: • Make sure every action is considered (e.g. ‘start game’) • Can other devices be involved (printer, computer, TV, other phones…)? • It’s not graded, so relax and have fun!

10. Next step in Development: Design • Requirements specification: • More of a contract about what a program will do • Design is an analysis and specification of how the system will do each task • It’s a plan • Companies hire Project Managers for this task • Need strong organization and Leadership skills • Need to build strong relationships in a team based environment • Lots of diagrams and flow charts • Less hands-on with the actual software, but the job is critical to success

11. Development: Implementation • Finally, the software is going to be made! • This is where programmers live • Need knowledge of design charts, terminology • Need strong programming skills • Problem Solving is key • More creative than you think! • Though you must follow directions, a programmer essentially starts with nothing and finishes with a complete product • Much like contractors who follow a blueprint and erect a building from a vacant lot

12. Development: Testing • Does the software work correctly? • Requires efforts from several levels: • Analysts check to make sure the specification is satisfied • Program managers check to make sure the design is fulfilled • Programmers check to make sure the code is accurate • Best practices in testing don’t wait until the end: • Each phase should be tested and re-tested frequently over the entire life of the product

13. Software Engineering Methodology • Classic approach to Software Engineering: The waterfall method • One task after the other • Need to get specification right on the first try, or the whole thing is a bust!

14. Modern Methodologies • Prototyping Methods • Open-source method • Extreme Programming

15. Prototyping • Prototype: initial invention/proof of concept that is meant to lead to a more refined product • Incremental Model: • Develop simplified version, perfect it, then • Add more complex features via program updates • Iterative Model • Develop simplified version, perfect it, then • ‘Throw it out’ and start over with a version 2.0 • Sometimes you get both: • Incremental versions 1.1,1.2, 1.3 • Iterative versions 1.X, 2.X • Example products for each model?

16. Open-Source Methodology • Write some code for ‘version 1’ • Publish it online, give it away for free • Community-based development: • People who appreciate the software will contribute so that it won’t ‘go out of business’ • Money • Time/effort/knowledge • Most people will take the software without paying for it • How do companies make money this way?

17. Extreme Programming • Referred to as an agile method • Form small teams ( < 12 ) • Program in pairs • Hold daily ‘mini-waterfalls’ to reevaluate progress and make changes quickly before they become big problems • Less formal, more flexible • Problems with this?

18. Testing • We’ll learn later that guaranteeing that a program always does what it is supposed to is impossible in complex projects • Glass-box testing • Creating tests with full knowledge of the source code and how it is supposed to work • Black-box testing • Creating tests with no knowledge of how the code works, but only knowing what the program is supposed to do • Good testing efforts use both types • Beta Testing: release the software to a small group initially, with no guarantees of quality • Just wait for the program to screw up!

19. Documentation • Nobody likes doing it, but it’s important • Large disconnect between the designer/ implementer and the standard computer user • Users WILL try things you never thought of! • Not their fault! • User documentation: your standard ‘how to use it’ manual • Technical documentation: installation guide • System documentation: description of system implementation; used by developers for maintenance • RTFM!!!!!

20. Your Niche in the Development Cycle • Computer Information Systems Analyst: • Systems analyst • Project Manager • Networking Systems Analyst: • Multi-level support to help all levels work together efficiently • Computer Science: • Programming • Research/Development • Digital Media & Design • Requirements Specification and Design (esp. interfaces)