CompSci 105 SS 2005 Principles of Computer Science Lecture 4 Lecturer: Santokh Singh

Parity Abstraction Modular Design Procedural Abstraction Data Abstraction Abstract Data Types Information Hiding Software Life Cycle Basic Stages Specification and Design Verification via Loop Invariants Costs Associated with Software

Hacking Type in a heap of code

Hacking Type in a heap of code Battle compilation errors

Hacking Type in a heap of code Battle compilation errors Run the code

Hacking Type in a heap of code Battle compilation errors Run the code If doesn’t work, change a random thing

Software Engineering Large Projects Team Development Guaranteed Results Easy Modification

Abstractions Complex Object Idealised Model Ignore Inessential Details

Class Reps Namelogin First meeting today/tomorrow (..)..time Place (CompSci …)

Parity Abstraction Modular Design Procedural Abstraction Data Abstraction Abstract Data Types Information Hiding Software Life Cycle Basic Stages Specification and Design Verification via Loop Invariants Costs Associated with Software

Modular (Class) Design System SecretCodes String Random

Procedural (Method) Design Encode SecretCodes Main Decode

Information Hiding Program that uses the String Class Implementation of the String Class API for the String Class

Data Abstraction int x = 14;

Software Life Cycle Specification Design Verify Code Test Refine Produce Maintain

Software Life Cycle Specification Design Verify Code Test Refine Produce Maintain

Agreeing on a method Suppose we want a method that adds two integers uses the add method implements the add method

What needs to be specified? Suppose we want a method that adds two integers public int add ( int x, int y )

What needs to be specified? Suppose we want a method that adds two integers // General Description: // Precondition: // Postcondition: public int add ( int x, int y )

Course Book We have been referring to the Course Book during lectures:- Pages : Numbers in the Computer Pages : Data Representations Please attend ALL classes for better understanding & for your own good.