1 International Diploma In Computer Studies (IDCS) 11th August 30th November 2008 P rogramming M ethods (PM)

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International Diploma In International Diploma In Computer Studies (IDCS)Computer Studies (IDCS)

11th August 11th August

30th November 200830th November 2008

PProgrammingrogramming

MMethodsethods

(PM)(PM)

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Programming Programming Methods (CT)Methods (CT)Programming Programming Methods (CT)Methods (CT)

Chapter 3Chapter 3

SECTION ASECTION ADDATA ANALYSIS ATA ANALYSIS AND PROBLEMSAND PROBLEMS

Chapter 3Chapter 3

SECTION ASECTION ADDATA ANALYSIS ATA ANALYSIS AND PROBLEMSAND PROBLEMS

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The software development The software development processprocess

Create structure diagrams for Create structure diagrams for structured programsstructured programs

Explain the different variables Explain the different variables typestypes

Organize InformationOrganize Information Analyze problemsAnalyze problems

Chapter OBJECTIVES:Chapter OBJECTIVES:

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The software development processThe software development process Data structures and data structures Data structures and data structures

diagramsdiagrams Organizing informationOrganizing information Fixed and Variable recordsFixed and Variable records

Chapter CONTENTS:Chapter CONTENTS:

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Chapter 3Chapter 3Data Analysis and Data Analysis and

ProblemsProblems


ProblemsProblems

PART 1PART 1ProgramProgram

Development Development ProcessProcess

PART 1PART 1ProgramProgram

Development Development ProcessProcess

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There are There are many different types of many different types of programsprograms which vary in complexity which vary in complexity from simple ones written as a hobby, from simple ones written as a hobby, to complex programs written by to complex programs written by profession programmers.profession programmers.

Which are part of a large systemWhich are part of a large system

1.1 Introduction1.1 Introduction

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ExampleExample : Hospital : Hospital Information SystemInformation System

Hospital information SystemHospital information SystemHospital information SystemHospital information System

Personnel DB

(Nurses, Doctors, etc)

Patients DB

(Emergency, OPD, etc)

Transaction DB

(Doctors + Patient,

Payments)

Inventory DB

(Drugs, Medical

Equipments)

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Some examples of Programs:Some examples of Programs: A suite in a A suite in a production control systemproduction control system A simple A simple database programdatabase program A program to perform A program to perform statistical statistical

analysisanalysis on experimental results on experimental results A program to display the contents of A program to display the contents of

database by a web processdatabase by a web process orders orders and payments. and payments. e-commerce applicationse-commerce applications On line bankingOn line banking

An An interactive multimediainteractive multimedia program program game (user interaction)game (user interaction) Encyclopedia (e-encyclopedia/ informative)Encyclopedia (e-encyclopedia/ informative)

1.2 Introduction (cont.)1.2 Introduction (cont.)

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Before writing any program we Before writing any program we need need

to know that:to know that: The The output requiredoutput required by the user from by the user from

the system the system The The processes necessaryprocesses necessary to produce to produce

this output for the userthis output for the user

The The data or inputdata or input to be processed to to be processed to create the output required create the output required

1.3 Introduction (cont.)1.3 Introduction (cont.)

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ProgrammerProgrammer Responsible for Responsible for writing computer writing computer

programsprograms

1.4 Key Terms Definition1.4 Key Terms Definition

System AnalystSystem Analyst Responsible for the Responsible for the

development of an development of an information systeminformation system

DesignsDesigns and and modifiesmodifies systems by turning user systems by turning user requirements into a set requirements into a set of of functional functional specificationsspecifications, which are , which are the blueprint of the the blueprint of the systemsystem

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1.5 Practical Analogy1.5 Practical Analogy An An Architect (system analyst)Architect (system analyst) and and

an an Engineer (programmer)Engineer (programmer)

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System System AnalysisAnalysis

The The analysis of analysis of the role of a the role of a proposed proposed systemsystem and the and the identification of identification of a set of a set of requirementsrequirements that the that the system should system should meet - the meet - the starting point starting point for systems for systems design.design.

1.6 Key Terms Definition 1.6 Key Terms Definition (cont.)(cont.)

Final Design Final Design Expected Expected

OutputOutput

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1.7 Program Specification1.7 Program Specification A A formal descriptionformal description of a system, or a of a system, or a

component or module of a system, component or module of a system, intended as a intended as a basis for further basis for further developmentdevelopment

CharacteristicsCharacteristics of a good specification of a good specification unambiguous, complete, verifiable, unambiguous, complete, verifiable,

consistent, modifiable, traceable, and usable consistent, modifiable, traceable, and usable after development after development

Details of the specification will be Details of the specification will be discovered during the discovered during the analysis analysis and and design stagesdesign stages of software of software development development

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1.7 Program Specification Example 1.7 Program Specification Example (cont.)(cont.)

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1.7 Practical Analogy: 1.7 Practical Analogy: Morning RoutineMorning Routine

PROCEDURES:PROCEDURES:

Step 1.Step 1. Get out of bed Get out of bed

Step 2.Step 2. Take a shower/bath Take a shower/bath

Step 3.Step 3. Dress yourself Dress yourself

Step 4:Step 4: Drink coffee/tea Drink coffee/tea

Step 5:Step 5: Take breakfast Take breakfast

Step 6:Step 6: Drive to work Drive to work

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1.7 Example: Actual Computer 1.7 Example: Actual Computer Program (Salary Computation)Program (Salary Computation)

Logical Program:Logical Program:

Step 1:Step 1: Identify all variables Identify all variables

Actual Program Code: Actual Program Code: VBVB

No. of hours worked, Rate per No. of hours worked, Rate per hourhour

Basic pay, Deductions, Net payBasic pay, Deductions, Net pay

Step 2:Step 2: Initialize all variables Initialize all variables

identify data typeidentify data typeDim no_hours_worked, Dim no_hours_worked,

rate_per_hour, basic_pay rate_per_hour, basic_pay

deductions, net_pay as deductions, net_pay as IntegerInteger

Step 3:Step 3: Assign variables Assign variables

(temporary storage)(temporary storage)Let a = no_hours_workedLet a = no_hours_worked

Let b = rate_per_hourLet b = rate_per_hour

Let c = basic_payLet c = basic_pay

Let d = deductionLet d = deduction

Let e = net_payLet e = net_pay

Step 4:Step 4: Compute basic pay Compute basic pay c = a * bc = a * b

Step 5:Step 5: Compute net pay Compute net pay e = c – de = c – d

Step 6:Step 6: Store value of net Store value of net paypay

lblPay.Caption = elblPay.Caption = e

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1.8 Definitions of Key 1.8 Definitions of Key TermsTerms

SpecificationSpecification A A formal descriptionformal description of a system or a of a system or a

component module of a system, component module of a system, intended as a basis for further intended as a basis for further developmentdevelopment

Specification LanguageSpecification Language A A languagelanguage that is used in expressing a that is used in expressing a

specification (e.g. Rational Rose UML)specification (e.g. Rational Rose UML)

Diagrammatic TechniqueDiagrammatic Technique A style of analysis that relies primarily A style of analysis that relies primarily

on the on the use of diagramsuse of diagrams (as opposed to (as opposed to text)text) DFD, flowcharts, MS ProjectDFD, flowcharts, MS Project

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1.9 Software Life Cycle1.9 Software Life Cycle The The program developmentprogram development process is process is

part of the software lifecycle, part of the software lifecycle, characterized by the following stages:characterized by the following stages:

Requirements Requirements analysis analysis

Design Design CodingCoding TestingTesting ImplementatioImplementatio

n and supportn and support

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1.10 Requirements 1.10 Requirements Analysis StageAnalysis Stage

An An accurate accurate and and complete set complete set of client and of client and user user requirementrequirementss is is produced to produced to determine determine the the characteristicharacteristics of an cs of an acceptable acceptable solutionsolution

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Practical Analogy: Practical Analogy: Building a Building a HouseHouse

House Owner House Owner RequirementsRequirements

Building Building RequirementsRequirements

(Site, Access)(Site, Access)Draft PlanDraft Plan Purpose/Purpose/

ObjectivesObjectives

Develop Initial Layout

Add further design considerations

(Porch, Parking, Pool)

Evaluate Improve Design

Building Objectives Cost, Season

Contractor, Materials

Building Objectives Design

Objectives

Final Design

Iterate

Initial Logical Modules

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1.10 Requirements 1.10 Requirements Analysis Stage (cont.)Analysis Stage (cont.)

The requirements analysis The requirements analysis specification specification

will contain:will contain: the the proposed system or solutionproposed system or solution, ,

which has been which has been agreed by the client agreed by the client and and developerdeveloper

a list of a list of existing tools, new tools,existing tools, new tools, required facilitiesrequired facilities and and peoplepeople available for developing the solution available for developing the solution

a a scheduleschedule for the next stages of the for the next stages of the project, including the deliverables for project, including the deliverables for each stage each stage

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1.10 Requirements 1.10 Requirements Analysis Stage (cont.)Analysis Stage (cont.)

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1.10.1 Deliverables 1.10.1 Deliverables Deliverables Deliverables

are the are the products of the products of the different different phasesphases throughout the throughout the development development process process

Provided for the client by the developer, Provided for the client by the developer, as as evidence that progressevidence that progress is being made is being made according to requirements according to requirements may be may be written documentswritten documents and and diagramsdiagrams

produced during the analysis and design produced during the analysis and design phases, phases, sample screen layoutssample screen layouts or or sample sample reportsreports

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1.10.2 Requirements 1.10.2 Requirements Analysis - Analysis - ObjectivesObjectives

To define, in detail, To define, in detail, a solutiona solution that will that will fully fully meet the client and user meet the client and user requirementsrequirements (program specification) (program specification)

The program specification will include a The program specification will include a description of the: description of the: InputsInputs to the process to the process operations the systemoperations the system performs for each input performs for each input output obtainedoutput obtained for the corresponding input for the corresponding input

• If there is more than one program in the system, If there is more than one program in the system, the document is called a system specification the document is called a system specification

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1.11 Design Stage1.11 Design StageHow the solution will be built to How the solution will be built to

satisfy thesatisfy the

requirements requirements Complex problems are Complex problems are divided into a set divided into a set

of sub-problems of sub-problems ProgramsPrograms and and modulesmodules are defined are defined

inputs, outputs, functions and processes inputs, outputs, functions and processes

The The use of formal program design use of formal program design techniquestechniques and programming standards and programming standards are recommended are recommended

The The most appropriate programming most appropriate programming languagelanguage will have been decided upon will have been decided upon during the development of the design during the development of the design

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1.11 Design Stage (cont.)1.11 Design Stage (cont.)

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1.12 Coding Stage1.12 Coding Stage Produce the Produce the

programsprograms that will that will make up make up the system the system

Complete Complete when all when all code is code is written and written and documenteddocumented, and , and compiles compiles without any without any errorserrors

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1.12 Testing Stage1.12 Testing Stage Every Every program module needs to be program module needs to be

testedtested according to the test plan according to the test plan developed in the design phase developed in the design phase

NOTE: can be carried out while program is being developed can be carried out while program is being developed Remember, finding and fixing a fault a fault after software delivery software Remember, finding and fixing a fault a fault after software delivery software

delivery is 100 more expensive than finding and fixing it than finding and delivery is 100 more expensive than finding and fixing it than finding and fixing it during systems analysis or early designfixing it during systems analysis or early design

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1.12 Testing Stage (cont.)1.12 Testing Stage (cont.) When the When the program is completedprogram is completed and all and all

separate modules have been tested, a separate modules have been tested, a full testfull test of the program is performed of the program is performed any errorsany errors in the program in the program will be will be

correctedcorrected and the test repeated and the test repeated If testing identifies If testing identifies changes requiredchanges required to to

the program design the program design analysis, design, coding and testing analysis, design, coding and testing

phases are repeated for the changes phases are repeated for the changes

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1.12 Testing Stage (cont.)1.12 Testing Stage (cont.) Systems testSystems test

programs are programs are tested as a grouptested as a group The system must be tested The system must be tested in all in all

environments environments Alpha testAlpha test

test of the finished application completed test of the finished application completed internallyinternally

Beta testBeta test tested tested externally externally

SimulationSimulation used when used when live environmentlive environment test is not test is not

possible, e.g. (nuclear reactor control, traffic possible, e.g. (nuclear reactor control, traffic light control) light control)

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1.13 Implementation 1.13 Implementation SupportSupport

If needs If needs change change andand the amendments the amendments required required are substantial, then the software lifecycle are substantial, then the software lifecycle would be applied to the amendments would be applied to the amendments

After installation it After installation it must be maintainedmust be maintained according to the needs of the users.according to the needs of the users.

When When all the all the previous stages previous stages have been have been completed completed satisfactorilysatisfactorily, the , the system is system is ready for ready for implementationimplementation

User User documentationdocumentation or or operating operating instructions may be instructions may be required required

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LifecycleLifecycle The The complete complete

lifetime of a lifetime of a software software systemsystem from from initial initial conception conception through to through to final final obsolescence obsolescence

The term is most commonly used in The term is most commonly used in contexts where programs are contexts where programs are expected to have a expected to have a fairly long useful fairly long useful lifelife

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1.14 Lifecycle Definition 1.14 Lifecycle Definition (cont.)(cont.)

LifecycleLifecycle Traditionally, a lifecycle is modeled Traditionally, a lifecycle is modeled

as a number of successive phases:as a number of successive phases: user requirements user requirements system requirementssystem requirements software requirementssoftware requirements overall design overall design detailed design detailed design component productioncomponent production component testing component testing integration and system testingintegration and system testing acceptance testing and releaseacceptance testing and release operation and maintenance operation and maintenance

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ProblemsProblems


ProblemsProblems

PART 2PART 2STRUCTURE DIAGRAMSSTRUCTURE DIAGRAMS

PART 2PART 2STRUCTURE DIAGRAMSSTRUCTURE DIAGRAMS

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Data StructureData Structure A way of describing the A way of describing the relationship of the relationship of the

componentcomponent parts to the whole parts to the whole

TechniqueTechnique A rectangle A rectangle containing a * means an iterationcontaining a * means an iteration

of all lower level boxes of all lower level boxes A box containing a A box containing a small circle represents a small circle represents a

choicechoice between alternative sets of data (a between alternative sets of data (a selection) selection)

*

IterationIteration

(Repetition)(Repetition)

SelectionSelection

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2.2 Structured Diagram 12.2 Structured Diagram 1

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2.4 Organizing Information 2.4 Organizing Information A A file file is composed of records is composed of records Each record Each record contains data organisedcontains data organised

in a defined structure in a defined structure The components of this structure are The components of this structure are

called called fieldsfields

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2.4 Data Structure Diagram 2.4 Data Structure Diagram (cont.)(cont.)

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2.5 Record Structure2.5 Record Structure The The fieldsfields in a record in a record must be must be

carefully designedcarefully designed to contain all the to contain all the data that may need to be referenced data that may need to be referenced for producing for producing information information this task would be this task would be performed in conjunction performed in conjunction

with the clientwith the client (e.g. name length, date (e.g. name length, date formats)formats) and the result would form part of and the result would form part of the program specification the program specification

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2.6 General File Structure2.6 General File Structure

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2.7 Fixed Length Records2.7 Fixed Length Records Number of characters allowed in each Number of characters allowed in each

record can be record can be predetermined predetermined (size (size specific)specific)

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2.8 Variable Length 2.8 Variable Length RecordsRecords

Sometimes records in a file store Sometimes records in a file store variable variable amounts of data amounts of data

It is It is not sensiblenot sensible to allow spare to allow spare capacity in the field lengths capacity in the field lengths this would be this would be highly inefficienthighly inefficient use of the use of the

backing store backing store the more complex processing requirements the more complex processing requirements

needed to deal with variable length records needed to deal with variable length records may be justified may be justified

it is the it is the responsibility of the design responsibility of the design teamteam to ensure that the to ensure that the processing/storage trade-offprocessing/storage trade-off is is sensibly chosen sensibly chosen

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Chapter SUMMARYChapter SUMMARY Program development process Program development process Structure diagrams Structure diagrams Organizing information Organizing information Fixed and variable length records Fixed and variable length records

1 International Diploma In Computer Studies (IDCS) 11th August 30th November 2008 P rogramming M ethods (PM)

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