INF354 Advanced Programming

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INF354 Advanced Programming

• Study Unit 2 Programming Part 2

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Study objectives

• Students must be able to
• Understand structured and modular programming
• Understand and use programming standards
• Do functions and procedures
• Do decision processing
• Do repetition processing

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Delphi Roadmap

• Delphi components
• Programming in Delphi

• Structured Programming
• Modular programming
• Object-oriented programming
• Standards
• Program design

• Programming steps
• Good programming practice
• Fundamental concepts and techniques

• Basic concepts
• Types of Applications
• Program Syntax
• Programming

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Structured Programs

• Programs
• That have modular design
• That only use three types of logical structures
• Sequence
• Decisions
• Loops
• Goto statements are not allowed

5
Delphi Roadmap

• Delphi components
• Programming in Delphi

• Structured Programming
• Modular programming
• Object-oriented programming
• Standards
• Program design

• Programming steps
• Good programming practice
• Fundamental concepts and techniques

• Basic concepts
• Types of Applications
• Program Syntax
• Programming

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Object-oriented programming (OOP)

• Sees real life entities as objects e.g.
  department, salary, person, car, invoice.
• Note all of the components in the IDE are also
  objects, e.g. the form, buttons, edit boxes, etc.
• Object-orientation (OO) emphasises re-use of
  code.

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Classes and Objects

• An objects type is called its class
• Creating a new object of a specific class is
  called instantiation
• I.e. an object is an instance of a class. E.g.
  Mr Jones is an object of class Employee

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Object

• An object consists of
• A description of its attributes called properties
  (also called instance fields, member fields,
  instance variables)
• The operations the object can perform called
  methods. Note that objects react to events.

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Object

• Exercise
• Open Delphi
• Open the Object Inspector (it will default to
  Form1)
• The Object Inspector contains 5 types of
  information
• The name of the class TForm1
• The name of the object Form1
• The objects properties
• The events that the object respond to and
  corresponding methods

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Object-oriented programming

• OOP has three fundamental concepts
• Encapsulation
• Combines the data and behaviour of an object in
  one package
• This provides data-hiding and re-use
• The user can manipulate an objects properties
  only by passing messages to the object, using the
  objects methods

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Object-oriented programming

• OOP has three fundamental concepts
• Inheritence
• Supports a parent-child relationship between
  objects
• For instance, a Manager class is a type of
  Employee class and can therefore inherit from it
• Inheritance allows the Manager class to inherit
  all of the Employee class properties and methods
• Inheritance creates a is a relationship between
  classes

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Object-oriented programming

• OOP has three fundamental concepts
• Polymorphism
• Literally the ability to appear in many forms
• Allows a program to process objects differently
  depending on their class
• E.g. performs addition for numbers,
  concatenation for strings and union for sets

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Delphi Roadmap

• Delphi components
• Programming in Delphi

• Structured Programming
• Modular programming
• Object-oriented programming
• Standards
• Program design

• Programming steps
• Good programming practice
• Fundamental concepts and techniques

• Basic concepts
• Types of Applications
• Program Syntax
• Programming

• Programming standards
• Naming conventions

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Programming standards

• Comments
• Use comments to describe major sections of the
  program
• Do not describe code itself, unless it is very
  complex or non-standard

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Programming standards

• Spacing and indentation
• Leave spaces between line, where needed, to make
  it more readable
• Put the different parts of decision or repetition
  structures on different lines and indent them
  appropriately

If A 1 then A A 1 else A 10
versus
If A 1 then A A 1 else A 10
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Programming standards

• General Programming
• Avoid mixed-mode arithmetic
• To convert from a string to a real value use Val
• To convert from a real to a string value use Str
• For integer values use StrToInt and IntToStr
• Expressions with multiple operators must use
  parentheses for clarity
• Avoid global parameters

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Delphi Roadmap

• Delphi components
• Programming in Delphi

• Structured Programming
• Modular programming
• Object-oriented programming
• Standards
• Program design

• Programming steps
• Good programming practice
• Fundamental concepts and techniques

• Basic concepts
• Types of Applications
• Program Syntax
• Programming

• Programming standards
• Naming conventions

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Naming conventions

• Hungarian notation
• Few mnemonics in front of name to show type
• Followed by a descriptive name
• Rules for mnemonics
• Remove vowels (except when type start with a
  vowel)
• Suppress duplicated consonants
• Suppress duplicated mnemonics by adding vowels
  back
• Examples
• edtAdress (type address)
• tblCustomer (type table)
• grpbxEmployee (type groupbox)

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Naming Conventions

• Names must be meaningful and descriptive
• Everything that will be used must be properly
  named (Dont leave default names)
• Distinguish parts by use of capitals
• Examples
• btnClientSave
• I, J,etc. (as counters)

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Naming Conventions

• Rules
• Variable names
• Lowercase
• Except for first letter of embedded words, which
  must be uppercase
• E.g. taxRate, numberOfLetters
• Subprogam, Object classes, Object variables and
  method names
• Must begin with uppercase letter
• Component names
• Start with prefix
• E.g. btnOK, edtInputValues

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Delphi Roadmap

• Delphi components
• Programming in Delphi

• Structured Programming
• Modular programming
• Object-oriented programming
• Standards
• Program design

• Programming steps
• Good programming practice
• Fundamental concepts and techniques

• Basic concepts
• Types of Applications
• Program Syntax
• Programming

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Program design

• Fundamental structure of a program is
• Input
• Process
• Output

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Program design

• Example 1 The Wastage program must work out the
  wastage when a sheet of metal is cut into equal
  sized parts.

edtLength
edtCutLength
edtWastage
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Program design

• Example 1 solution
• var
• totlength, cutlength, wastage integer
• begin
• totlength strtoint(edtLength.text)
• cutlength strtoint(edtCutLength.text)
• wastage totlength mod cutlength
• edtWastage.text inttostr(wastage)
• end

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Program design

• Step 1 Identify inputs and outputs

inputs
output
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Program design

• Step 2 Identify and declare variables and their
  types
• Input related variables
• totlength total length of metal
• cutlength cut length of metal
• Processing related variables
• wastage stores calculated wastage
• Output related variables
• None
• var
• totlength, cutlength, wastage integer

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Program design

• Step 2 Handle inputs
• // Input
• totlength strtoint(edtLength.text)
• cutlength strtoint(edtCutLength.text)

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Program design

• Step 3 Handle processing
• // Calculate wastage
• wastage totlength mod cutlength

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Program design

• Step 4 Handle output
• // Display wastage
• edtWastage.text inttostr(wastage)

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Program design
Example 1 solution with comments var totlength,
cutlength, wastage integer begin //Input totle
ngth strtoint(edtLength.text) cutlength
strtoint(edtCutLength.text) //Calculate
wastage wastage totlength mod
cutlength //Display wastage edtWastage.text
inttostr(wastage) end
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Program design
Example 1 An alternative solution var begin //C
alculate and display wastage edtWastage.text
inttostr (strtoint(edtLength.text) mod
strtoint(edtCutLength.text)) end
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Program design
Example 2 Read the input and display the
number of capital E s
edtInput
lblDisplay
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Program design
Example 2 Solution var wordent string
lenword, ecount, letpos integer begin
ecount 0 letpos 1 wordent
edtInput.text lenword length(edtInput.text)
repeat if copy(wordent,letpos,1) 'E'
then ecount ecount 1 letpos
letpos 1 until letpos gt lenword
lblDisplay.Caption Inttostr(ecount) end
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Program design
Example 2 Solution Step 1 (Identify inputs and
outputs)
Input
Output
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Program Design

• Step 2 Identify and declare variables and their
  types
• Input related variables
• wordent to store input word
• Processing related variables
• lenword stores the length of the word
• ecount stores the number of Es
• letpos stores the position of E
• Output related variables
• None
• var
• wordent string
• lenword, ecount, letpos integer

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Program Design

• Step 3 Handle input
• // Input
• wordent edtInput.text

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Program Design

• Step 4 Handle processing
• //Initialise
• ecount 0
• letpos 1
• lenword length(edtInput.text)
• //For every letter, see if it is a E. If it is,
  add 1 to E-counter
• repeat
• if copy(wordent,letpos,1) 'E' then
• ecount ecount 1
• letpos letpos 1
• until letpos gt lenword

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Program Design

• Step 4 Handle outputs
• //Display E-counter
• lblDisplay.Caption IntToStr(ecount)

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Delphi Roadmap

• Delphi components
• Programming in Delphi

• Modules
• Decisions
• Repetition
• Object-orientation
• Database
• Files
• Reports
• Interfacing

• Programming steps
• Good programming practice
• Fundamental concepts and techniques

• Basic concepts
• Types of Applications
• Program Syntax
• Programming

• Goto, Exit
• Procedures
• Functions
• Passing parameters
• Recursion

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Procedures and functions

• One of the ways of ensuring modular programming
  is by using procedures and functions
• They give a name to a group of statements that
  accomplish a specific task
• Difference between procedures and functions
• Function returns a value that may be used in an
  expression

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Procedures and functions

• Make programs more readable, therefore less error
  prone
• Make programs easier to debug
• Code can be reused in other programs
• May be either standard (built-in) or user-defined

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Delphi Roadmap

• Delphi components
• Programming in Delphi

• Modules
• Decisions
• Repetition
• Object-orientation
• Database
• Files
• Reports
• Interfacing

• Programming steps
• Good programming practice
• Fundamental concepts and techniques

• Basic concepts
• Types of Applications
• Program Syntax
• Programming

• Goto, Exit
• Procedures
• Functions
• Passing parameters
• Recursion

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Goto and Exit

• Not part of structured programming
• But used in real programming
• It should be avoided, everything can be done with
  structured control statements
• If used, use in a controlled manner

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Goto

• Example
• procedure xxx
• label SmallSalary, BigSalary
• begin
• if Salary lt 1000 and Salary gt 0 then
• goto SmallSalary
• if Salary gt 1000 then
• goto BigSalary
• if Salary lt 0 then
• goto 9000
• SmallSalary
• WriteLn(Poor man)
• BigSalary
• WriteLn(Rich Man)
• 9000
• WriteLn(Wrong Input)
• end

PROBLEM!
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Exit

• Example
• procedure xxx
• label SmallSalary, BigSalary
• begin
• if Salary lt 1000 and Salary gt 0 then
• goto SmallSalary
• if Salary gt 1000 then
• goto BigSalary
• if Salary lt 0 then
• goto 9000
• SmallSalary
• WriteLn(Poor man)
• Exit
• BigSalary
• WriteLn(Rich Man)
• Exit
• 9000
• WriteLn(Wrong Input)

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Goto and Exit

• Declaring labels
• label labelName1, , labelNamen
• Use a label
• labelName statement
• Unconditional branch (jump) to a label
• goto labelName
• Pass control immediately from current subprogram
  to the calling program
• Exit

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Delphi Roadmap

• Delphi components
• Programming in Delphi

• Modules
• Decisions
• Repetition
• Object-orientation
• Database
• Files
• Reports
• Interfacing

• Programming steps
• Good programming practice
• Fundamental concepts and techniques

• Basic concepts
• Types of Applications
• Program Syntax
• Programming

• Goto, Exit
• Procedures
• Functions
• Passing parameters
• Recursion

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Procedures

• May be used instead of a statement
• Structures a program to improve clarity and
  generality

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Calling Procedures

• Procedure example 1
• Begin
• NumIn 16
• SquareRoot(NumIn,NumOut)
• SquareResult NumOut
• End
• SquareRoot is the name of a procedure
• NumIn and NumOut are the arguments of the
  procedure
• These arguments are passed to the procedure
• Executing the statement will execute the
  corresponding procedure
• This requires the procedure to be defined
  beforehand

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Defining Procedures

• Procedure example 1
• procedure SquareRoot(InValue real var OutValue
  real)
• begin
• OutValue sqrt(InValue)
• end
• Invalue and OutValue are the parameters of the
  procedure
• They correspond to the arguments passed
• The names of the arguments and parameters do not
  have to be the same
• They must however agree in type
• Order is important. The first argument
  corresponds to the first parameter, the second
  argument to the second parameter, etc.
• These arguments can be any expression that is the
  same type as the parameter

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Procedure flow of data
Begin NumIn 16 SquareRoot(NumIn,NumOut) Sq
uareResult NumOut End
procedure SquareRoot(InValue real var OutValue
real) begin OutValue sqrt(InValue) end
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Procedure flow of data
Begin NumIn 16 SquareRoot(NumIn,NumOut) Sq
uareResult NumOut End
procedure SquareRoot(InValue real var OutValue
real) begin OutValue sqrt(InValue) end
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Procedures
Exercise Create a procedure called TitleCase to
capitalize the first letter of every word in an
input sentence
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Procedures

• Answer

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Delphi Roadmap

• Delphi components
• Programming in Delphi

• Modules
• Decisions
• Repetition
• Object-orientation
• Database
• Files
• Reports
• Interfacing

• Programming steps
• Good programming practice
• Fundamental concepts and techniques

• Basic concepts
• Types of Applications
• Program Syntax
• Programming

• Goto, Exit
• Procedures
• Functions
• Passing parameters
• Recursion

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Functions

• A function may be used instead of a variable

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Calling Functions

• Function example 1
• Begin
• NumIn 16
• SquareResult SquareRoot(NumIn,NumOut)
• End
• SquareRoot is the name of a function
• NumIn and NumOut are the arguments of the
  function
• These arguments are passed to the function
• Executing the statement will execute the
  corresponding function
• This requires the function to be defined
  beforehand

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Defining Functions

• Function example 1
• function SquareRoot(InValue real) real
• begin
• SquareRoot sqrt(InValue)
• end
• A function results in a value being assigned to
  its name upon execution of that function
• The value of the result of the function will be
  of type real
• The function identifier SquareRoot must be
  assigned a value within the function block
• The function identifier
• May not be used like a variable
• It may only be assigned a value
• It cannot be tested or accessed
• Invalue is the parameter of the function

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Function - flow of data
Begin NumIn 16 SquareResult
SquareRoot(NumIn) End
procedure SquareRoot(InValue real)
real begin SquareRoot sqrt(InValue) end
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Function - flow of data
Begin NumIn 16 SquareResult
SquareRoot(NumIn) End
procedure SquareRoot(InValue real)
real begin SquareRoot sqrt(InValue) end
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Functions

• Exercise
• Create a function to calculate the maximum value
  of 5 integer values entered

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Functions

• Answer

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Delphi Roadmap

• Delphi components
• Programming in Delphi

• Modules
• Decisions
• Repetition
• Object-orientation
• Database
• Files
• Reports
• Interfacing

• Programming steps
• Good programming practice
• Fundamental concepts and techniques

• Basic concepts
• Types of Applications
• Program Syntax
• Programming

• Goto, Exit
• Procedures
• Functions
• Passing parameters
• Recursion

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Passing parameters

• Parameters can be passed either
• By reference
• Actually passes address of argument, not
  arguments value
• Thus, subprogram can change argument variables
  value
• By value
• Passes value of argument to the subprogram
• Subprogram access copy of the argument variable
• Thus, subprogram cannot change value of variable
• Delphis default

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Passing parameters Pass by value
var value Integer begin value 5
WriteLn(Start Test value
IntToStr(value) TimesProcedure(value)
WriteLn(Start Test value
IntToStr(value) End
Output Start Test value
5 Start TimesProcedure number 5 End
TimesProcedure number 10 End Test
value 5
procedure TimesProcedure(number Integer) begin
WriteLn(Start TimesProcedure number
IntToStr(number) number number 2
WriteLn(End TimesProcedure number
IntToStr(number) end
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Passing parameters Pass by reference
Output Start Test value
5 Start TimesProcedure number 5 End
TimesProcedure number 10 End Test
value 10
var value Integer begin value 5
WriteLn(Start Test value
IntToStr(value) TimesProcedure(value)
WriteLn(Start Test value
IntToStr(value) End
procedure TimesProcedure(var number
Integer) begin WriteLn(Start TimesProcedure
number IntToStr(number) number
number 2 WriteLn(End TimesProcedure
number IntToStr(number) end
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Delphi Roadmap

• Delphi components
• Programming in Delphi

• Modules
• Decisions
• Repetition
• Object-orientation
• Database
• Files
• Reports
• Interfacing

• Programming steps
• Good programming practice
• Fundamental concepts and techniques

• Basic concepts
• Types of Applications
• Program Syntax
• Programming

• If
• Case

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Decisions

• Two types of decisions
• Binary choice if
• Multiple choice case

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Delphi Roadmap

• Delphi components
• Programming in Delphi

• Modules
• Decisions
• Repetition
• Object-orientation
• Database
• Files
• Reports
• Interfacing

• Programming steps
• Good programming practice
• Fundamental concepts and techniques

• Basic concepts
• Types of Applications
• Program Syntax
• Programming

• If
• Case

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If
Example 1 (If without an else) Graphical
representation
False
True
gender M
Display Male
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If
Example 1 (If without an else) Delphi
if gender M then Display Male
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If
Example 2 (If without an else) Graphical
representation
True
False
gender M
Display Male
Display Female
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If
Example 2 (If without an else) Delphi
if gender M then Display Male else Display
Female
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If
Example 3 (Multiple lines) Graphical
representation
True
False
gender M
Display Male Inc(maleCount)
Display Female Inc(femaleCount)
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If
Example 3 (Multiple lines) Delphi
if gender M then begin Display(Male) maleC
ount maleCount 1 end else
begin Display(Female) femaleCount
femaleCount 1 end
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If
Example 4 (else if) Graphical representation
True
sal lt 100
Display Small
False
sal gt 100 and sal lt 1000
True
Display Medium
False
True
sal gt 1000
Display Big
False
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If
Example 4 (else if) Delphi
if sal lt 100 then Display(Small) else if sal
gt 100 and sal lt 1000 Display(Medium) else if
sal gt 1000 Display(Big)
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If
Example 5 (nested if) Graphical representation
False
True
gender M
True
True
False
age lt 65
age lt 65
Display Mom
Display Grandma
Display Dad
Display Granddad
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If
Example 5 (nested if) Delphi
if gender M then if age lt 65
then Display(Dad) else
Display(Granddad) else if age lt 65
then Display(Mom) else
Display(Grandma)
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If

• Nested ifs
• The following code has two possible
  interpretations
• Rule each else is associated with the nearest
  available if.

if exp1 then if exp2 then statement1 else
statement2
if exp1 then if exp2 then statement1
else statement2
if exp1 then if exp2 then statement1
else statement2
?
?
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If

• Hint
• Always use compound statements within your if
  statement, even if you only have one statement in
  it

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Delphi Roadmap

• Delphi components
• Programming in Delphi

• Modules
• Decisions
• Repetition
• Object-orientation
• Database
• Files
• Reports
• Interfacing

• Programming steps
• Good programming practice
• Fundamental concepts and techniques

• Basic concepts
• Types of Applications
• Program Syntax
• Programming

• Goto
• If
• Case

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Case
Example 1 Graphical representation
True
1..99
Display Small
False
True
Display Medium
100..999
sal
False
True
else
Display Big
False
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Case
Example 1 Delphi
case sal of 1..99
Display(Small) 100..999
Display(Medium) else
Display(Big) end
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Delphi Roadmap

• Delphi components
• Programming in Delphi

• Modules
• Decisions
• Repetition
• Object-orientation
• Database
• Files
• Reports
• Interfacing

• Programming steps
• Good programming practice
• Fundamental concepts and techniques

• Basic concepts
• Types of Applications
• Program Syntax
• Programming

86
Repetition

• Example 1 Compute the sum of integers 1 - 10

Sum ? 0 Number ? 1
Sum ?Sum Number Number ?Number 1
NO
Number gt10?
YES
Display Sum
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Walkthroughs
Sum ? 0 Number ? 1
Sum ?Sum Number Number ?Number 1
NO
Number gt10?
YES
Display Sum
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Repetition

• Always involves
• Initialisation of values
• Incrementing of a counter or
• moving forward (e.g. next record in file)
• Testing of values

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Repetition
Sum ? 0 Number ? 1
Initialising values
Sum ?Sum Number Number ?Number 1
Incrementing values
NO
Testing values
Number gt10?
YES
Display Sum
90
Repetition

• Delphi program of example 1
• var Sum, Number Integer
• begin
• Sum 0
• Number 1
• repeat
• Sum Sum Number
• Number Number 1
• until number gt 10
• writeln (Sum)
• end

91
Repetition
Delphi program of example 1 var Sum, Number
Integer begin Sum 0 Number
1 repeat Sum Sum Number Number
Number 1 until number gt 10 writeln
(Sum) end
92
Repetition

• Notes
• Number is the loop control variable or counter
  variable in example 1
• The counter variable controls the number of times
  the loop will execute
• Always check the initial and end value of a
  counter variable
• Many times programmers make a mistake of one too
  many or one too little times through the loop

93
Exercise 1

• Make example 1 more general by allowing n (not
  just 10) times through the loop and a variable
  increment (not just 1)

94
Exercise 1

• Flowchart and walkthrough (Yours)

95
Exercise 1
Flowchart and walkthrough (Given)
96
Exercise 1
Program