ITM207 Exam Notes- Ch 9.docx

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Information Technology Management
ITM 207
Jim Tam

Chapter 9 Object-oriented Design-A problem-solving methodology that produces a solution to a problem in terms of self-contained entities called objects  Breaks up problems into collaborating objects (top-down breaks into tasks) Problems are solved by 1. isolating the object 2. abstract the object with like properties and actions into groups(class) 3. determining the responsibilities of the group in interacting with other groups Object  A thing or entity that makes sense within the context of the problem. For example, a student, a car, time, date  concrete example of class  is an instance of class Class- A description of a group of similar objects  contain fields that represent the properties(name, eye color) and behavior(responsibilities)(cook, clean) of the class Instance of Class- is a specific realization of any object. Method- A named algorithm that defines behavior (shop, cook) Decomposition Brainstorming- to locate possible classes Filtering- the classes to find duplicates or remove unnecessary ones to find core classes in solution Scenarios- are tried to be sure we understand collaborations  Assign responsibilities to each class  Knowledge Responsibilities- what a class must know about itself  Behavior Responsibilities- what a class must be able to do  Encapsulation- the bundling of data and actions in a way that the logical properties are separated from the implementation details Responsibility algorithms-are designed for all actions that classes must exhibit  Knowledge responsibilities usually just return the contents of one of an object’s variables  Action responsibilities are a little more complicated, often involving calculations High-level language- A language that provides a richer (more English-like) set of instructions Compiler- A program that translates a high-level language program into machine code Interpreter- A translating program that translates and executes the statements in sequence  Assembler or compiler produce machine code as output, which is then executed in a separate step  An interpreter translates a statement and then immediately executes the statement  Interpreters can be viewed as simulators Java(1996)  Portability(run on any machine) was the primary importance  Compiled using Bytecode(language)  JVM(Java Virtual Machine) interprets the Bytecode and executes it Programming Language Paradigms Imperative Paradigm- Program describes the processing -Procedural  Characterized by sequential instructions  A program in which statements are grouped into a hierarchy of subprograms  Fortran, C, C++ -Object-oriented model  Program consists of a set of objects and the interactions among the objects  Python, Java, Smalltalk, Simula C++ is a procedural language with some object-oriented features Java is an object-oriented language with some procedural features Declarative Paradigm- Program describes the results -Functional  Based on the mathematical concept of a function  Lisp, Scheme, and ML -Logic  Based on principl
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