PC204. Lecture 5 Programming Methodologies. Copyright 2000 by Conrad Huang and the Regents of the University of California. All rights reserved.

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2 Programming Paradigms Software Engineering Exploratory Programming

3 Software Engineering Requirements Specification Design Coding Verification Debugging Documentation Dissemination Maintenance Enhancement

4 Why Doesn t It Work (for us)? Fuzzy requirements The most important phase is often is least well defined, especially in a research environment

5 Exploratory Programming Faster feedback loop Standard components Reusable components Rapid Application Development (RAD)

6 Methodologies Functional decomposition Structured programming Modular programming Object-oriented programming Generic programming Extreme programming Agile programming

7 What s the Difference? Methodologies may be applied for any programming language Some languages are easier (or harder) to use with some methodologies The outward appearance of a program is frequently determined by the language, but the methodology may be discerned from code organization

8 Evaluation Criteria Correctness Maintainability Flexibility Reusability

9 Functional Decomposition Divide problem into phases Flowchart diagrams Input, compute, output Algorithm for each phase Fortran Correctness - okay Maintainability - okay Flexibility - limited Reusability - limited

10 Functional Decomposition yes no yes loop no

11 Structured Programming Local organization No go to s Use functions Characterized as just indentations by unbelievers Fortran, C, Pascal Correctness - okay Maintainability - better more readable code Flexibility - okay simpler to reorganize Reusability - better reuse functions

12 Structured Programming Function yes Function no yes no loop

13 Modular Programming Group related data and functions together Module functions operate on module data Interface vs. Implementation Data abstraction and data encapsulation C, Algol, Ada Correctness - good module-based testing Maintainability - good localized changes Flexibility - better Reusability - better reuse entire modules

14 Modular Programming Module Module Module

15 Object-oriented Programming Formalize convention of always passing module data structures to module functions Class: definition of data and the functions that operate on them Object: data created from class definition Smalltalk, C++, Java Correctness - good Maintainability - better guaranteed internal consistency Flexibility - better Reusability - better reuse concepts

16 Object-oriented Programming Instance Instance Class Instance Instance Class

17 Generic Programming Back to algorithms Objects that share the same interface can be generically manipulated Toolkits of objects and algorithms

18 What Is A Good Design? Too few classes, and code is limited in flexibility and reusability lacks cohesion Too many classes, and code is more difficult to verify and maintain too much coupling Design is still an art form

19 Design vs. Coding Coding from a design is much simpler than hacking because most of the hard work has been done Sometimes you have to hack to find the right design Ouch Coding Design Evaluation Deployment Debugging

20 Object-oriented Programming Languages that support object-oriented programming have built-in concept of class In addition to design, object-oriented programming also features inheritance Base class defines behavior; derived class defines new or redefines base behavior Simplifies code reuse

21 Reference Material Object Oriented Design with Applications, Grady Booch Object-oriented Software Construction, Bertrand Meyer Software Tools, Brian Kernighan, et al.

ITC213: STRUCTURED PROGRAMMING. Bhaskar Shrestha National College of Computer Studies Tribhuvan University

ITC213: STRUCTURED PROGRAMMING Bhaskar Shrestha National College of Computer Studies Tribhuvan University Lecture 03: Program Development Life Cycle Readings: Not Covered in Textbook Program Development