CSC335-Chapter1

8/13/2019 CSC335-Chapter1

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Instructor:

Ahmad Reza Hadaegh

(Chapter 1Software Development)

CSC-335

Data Structures and Algorithms

The content of this power point lecture has been originallycreated by Christos Kolonis and modified by

Dr. Ahmad R Hadaegh


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Chapter Contents

1.1 Problem Analysis and Specification1.2 Design

1.3 Coding

1.4 Testing, Execution, and Debugging1.5 Maintenance


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Chapter Objectives

Introduce software development approaches Contrast software development in programming course

with real world

Study top-down, objected oriented approaches

Introduce design aspects

Select or build data types

Develop algorithms for operations on data

Investigate error types

Emphasize importance of testing

Note time and effort devoted to maintenance


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5 Phases of Software Life Cycle

Waterfall Model


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5 Phases of Software Life Cycle

Realistic Waterfall Model


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1.1 Problem Analysis and Specification

CS courses

small systems

few hundred lines ofcode

simple, straightforward

self-contained

Real world large systems

thousands of lines ofcode

complex

many components

problem initially poorlydefined

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1.1 Problem Analysis and Specification

The specification or "contract" will include Purpose

Precondition

Postcondition

Real world contracts

Must be precise

May be required to prove end product meets these

precise specifications


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1.2 Top Down Design

Original problem partitioned into simpler subproblems

Each of these sub problems likewise subdivided


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1.2 OOD: Object-OrientedDesign

Identify the objectsinthe problem'sspecification and theirtypes.

Identify the operationsor tasks to manipulatethe objects

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1.2 OOD: Object-OrientedDesign

UML class diagram

Fig. 1.7


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1.2 Data Types of the Objects

Simple Structured

arrays

structures

Class objects

Think of them

as Containers


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1.2 Algorithms

Pseudo code Must be

Definite, unambiguous

Simple

Finite

correct and efficient

well structured

Cannot separate data structures from algorithms


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1.2 Algorithms

Unstructuredgoto's

if-else's

Structured

while loop

switch stmt

Fig. 1.8(a)

Fig. 1.8(b)


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1.3 Coding

Select language of implementation Encode the design

Example Figure 1.9 Financial-aid update function

Figufre 1.10 Test-driver for Financial-aid updatefunction

Figure 1.11 Header file forFinancialAidAwardclass

Figure 1.12 Implementation file forFinancialAidAwardclass

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1.3 Coding

Verify integration combining program units into a complete

software system.

Insure quality

programs must be correct, readable, andunderstandable

well-structured, documented, formatted for

readability


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1.4 Testing, Execution, and Debugging

Validation:"Are we building the right product?"

check that documents, program modules, etc.match the customer's requirements.

Verification:"Are we building the product right?"

check that products are correct,

complete,

consistent with each other and with those of thepreceding phases.

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1.4 Different Kinds Of Tests Required

Unit tests: Each individual program unit works?

Program components tested in isolation

Integration tests :

Units combined correctly?

Component interface and information flow tested

System tests:

Overall system works correctly?

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The "V" Life Cycle Model

FIG. 1.13


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Types of Errors

Syntax errors errors in the grammar of the programming language

Ex: forgetting ; at the end of the sentence.

Run-time errors

happen during program execution

Ex: Division by zero

Logic errors

errors in algorithm design

Ex: instead of a = b + c you have written a = b - c


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Black Box or Functional Test

Outputs produced for various inputs

Checked for correctness

Do not consider structure of program component

itself. Program unit is viewed as a black box

Accepts inputs and produces outputs,

Inner workings of the box are not visible.

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White Box or Structural Test

Performance is tested examine codes internal structure.

Test data is carefully selected

specific parts of the program unit are exercised.

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Shows what

is going on


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Maintenance

Large % of

Computer center budgets

Programmer's time

Software development cost

Because

Includes modifications and enhancements

Poor structure, poor documentation, poor style

Bug finding and fixing is tougher

Delays implementation of enhancements

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