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Dr Derek Peacock 2014 1

Introduction to Software Development

by Derek Peacock

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What is a Computer ?

Electronic InformationProcessingMachine

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Basic System

InputData

(CPU)Processor

Output Data

Program

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Computer Programs

A sequence of coded instructions fed into a computer to enable it to perform specified operations upon data

Program = Set of cooperating Classes

Class = Operations and Data

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Operations

Procedures for the solution to a problem in a finite number of steps

1. Get the amount in GBP2. Get the exchange rate3. Calculate the amount in Euros4. Display the result in Euros

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Data & Data Structures

ObservationsFactsMeasurementsAttributesValuesReal or imaginary

ListsQueuesStacksTablesRecordsTrees

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Program Languages

Machine CodeC/C++/C#Visual Basic JavaPascal(Delphi)COBOLSQL

AssemblerPL/1ADASmall TalkSNOBOLFORTRANLISP

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Machine Code (Low Level)

0E E8 D9 010E E8 45 02B8 3E 01 1E50 1E 50 B8

‘AssemblerLD A, 01LD B, 02Add A, B

Total FlexibilityVery FastMany InstructionsDifficult to readDifficult to Debug

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Operations in English

Work out the equivalent amount in Euros for a given amount in GBP

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English

ImpreciseAmbiguousVery Large DictionarySame word can have different meaningsRules of grammar complex and inconsistent

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C#.NET

Easier to LearnVisual DesignObject OrientedMicrosoft Support .NET supportVisual Studio IDE

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C# Operation or Method

Console.WriteLine("Starting Convert Pounds to Euros!");Console.WriteLine();

Console.Write("Enter amount in British Pounds £ >");string value = Console.ReadLine();pounds = Convert.ToDecimal(value);euros = pounds * 1.2471m;

Console.WriteLine("Euros = {0}", euros);Console.WriteLine();Console.WriteLine("Ending Convert Pounds to Euros!");

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Java

Platform IndependentNot by Microsoft (by Oracle)Object OrientedWeb integrationVisual IDEsEnterprise Level and Mobile device support

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Java Operation

private void calculate_Euros(){inputAmount = InputTextBox.getText()exchangeRate = RateTextBox.getText()

Euros = inputAmount * exchangeRate

OutputAmountTextBox.setText(euros)

}

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C++

Leading LanguageSystems LanguageFast ExecutionObject Oriented

Main()

{

scanf(“%d”, &GBP);

scanf(“%d”, &ERate);

Euros = GBP * ERate

printf(“Euros = “);

printf(“%d”, Euros);

}

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Compilation (translatation)

High LevelLanguage

Input Program

Compiler ObjectCode

Output

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Linking (using pre-built libraries)

CompiledLibraries

MachineCodeLinker

ObjectCode

Input Program Output

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Execution (Run Program)

Input Program Output

Data MachineCode Results

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Software Development Life Cycle

Terms of Reference

RequirementsAnalysis

Software Design

Implementation

Testing

What ? (Outline)

What ? (Detail)

How ?

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Terms of Reference

I need a program that I can use to calculate how many euros I will get for a given amount of British currency.

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User Requirements

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Software Design

EnterPounds

CalculateEuros

DisplayEuros

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Delphi Implementation

procedure ConvertToEuros();var

pounds : currency;euros : currency;ExchangeRate : Double;

begin

pounds := GbpTextBox.Text;ExchangeRate := ExchangeRateTextBox.text;

euros := pounds * ExchangeRate;

EurosTextBox.Text := “Euros = ” & euros;

end;

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Testing

Function Tested

Data Used Expected Result

Actual Result

Calculate GBP = 400Rate = 1.5

Euros = 600 Euros = 600

Calculate GPB = Rate =

Error Message

Error Message

Calculate GPB = -400Rate = 1.5

Error Message

Euros = -600