Alyce Brady, Kalamazoo College Software Engineering Friday, Week 4

Alyce Brady, Kalamazoo College Evolution of Software Engineering Single-person projects: “Back of the envelope” design followed by coding, debugging Multiple-person projects: More formal design, identify modules, code modules, group debugging of whole project

Alyce Brady, Kalamazoo College Engineering = cost-effective solutions to practical problems by applying scientific knowledge in building things in service of mankind Science Production Engineering Commercial Craft Mary Shaw, Carnegie Mellon University

Alyce Brady, Kalamazoo College Evolution of Software Engineering Improved quality: –formal design (e.g., structured or object-oriented design) –identify modules –develop a test plan based on the design –code modules –develop test plan of individual module based on code –test modules in isolation –test integrated whole

Alyce Brady, Kalamazoo College Why Are All These Steps Necessary? Writing a program is much easier than writing a programming system, which is much easier than writing a programming system product which is documented thoroughly usable in many environments robust in its operations F. Brooks estimated that each is at least 3 times more expensive than the previous.

Alyce Brady, Kalamazoo College Why Software Engineering? Barry Boehm has estimated that specification errors repaired in later stages of software development can cost as much as 100 times more to fix than if caught at specification time.

Alyce Brady, Kalamazoo College Evolution of Software Engineering  Software Lifecycle –Requirements Analysis –System Specification –Design –Implementation (programming) –Unit Testing –Integration Testing –Maintenance (fixing problems, adding enhancements)

Alyce Brady, Kalamazoo College Waterfall Lifecycle Requirements System Spec. Design Code, Unit Test Integration Test

Alyce Brady, Kalamazoo College “Over-the-Wall” Lifecycle Implementation Unit Testing Integration Requirements System Spec. Design

Alyce Brady, Kalamazoo College Modified Waterfall Lifecycle Requirements System Spec. Design Code, Unit Test Integration Test

Alyce Brady, Kalamazoo College Whirlpool Lifecycle Req. Sys. Spec. Design Code Unit Test Integration

Alyce Brady, Kalamazoo College Levels of Abstraction –Requirements Analysis –System Specification –Design –Implementation (programming)

Alyce Brady, Kalamazoo College Types of Testing “Black box” testing –based on Requirements Analysis, System Specification –test plan developed before design; run as part of integration testing “Gray box” testing –based on Detailed Design –test plan developed before implementation; run as part of integration testing (some may be part of unit testing) “White box” testing –based on Implementation (code) –unit testing

Alyce Brady, Kalamazoo College Levels of Abstraction –Requirements Analysis –System Specification –Design –Implementation (programming) –Unit Testing –Integration Testing –Maintenance (fixing problems, adding enhancements)

Alyce Brady, Kalamazoo College Object Oriented Programming Based on modeling from the real world. It’s a way of thinking about a problem abstractly using real-world concepts, rather than computer concepts. JavaScript is object-based but not completely object-oriented.

Alyce Brady, Kalamazoo College Object-Oriented Organize software as a collection of discrete objects that have both behavior and information. Objects then interact with each other to perform their tasks. Objects have values (or information) and operations (or behaviors).

Alyce Brady, Kalamazoo College Object-Oriented The object values could be name or size. The object operations could be changing or displaying the values. The values and operations are grouped together to make a class.

Alyce Brady, Kalamazoo College Object-oriented Example Class: Car Attributes (or values) –Color –Make –Model Operations: –TurnRight –TurnLeft –Accelerate –Brake –Repair Object - Mike’s car is a new blue, Mazda 626 Car. Mike’s car then has values of color (blue), a make (Mazda), a model (626). Mike’s car then can do operations like TurnLeft, Accelerate, Brake and TurnRight.

Alyce Brady, Kalamazoo College In Class Exercise Design a class that describes a fish. –What attributes would a fish have? –What operations could a fish do? Create a new fish with attributes of its own and design a short series of actions the fish might do.