Structured Problem Solving

1
Structured Problem Solving

• Object- Oriented Concepts 1

2
Objectives

• After completing the work and attending this
  session you will
• Understand what is meant by an object-oriented
  approach to computing
• Understand the terms attribute, status and
  protocol

3
The idea of Objects

• An object is a piece of software that can receive
  and act on a message sent to it.
• On the right is a piece of text. This is can be
  regarded as an object
• We can send it messages.

The Quick brown fox jumps over the lazy dog.
4
Sending Messages to Objects

• Bold on
• Italic on
• Bold, Italic off
• Font Size 30
• Font Colour Red
• Font Comic Sans
• Font Colour Green Copperplate Gothic Size 36
  Italic

The Quick brown fox jumps over the lazy dog.
5
Sending Messages to Objects

• Bold on
• Italic on
• Bold, Italic off
• Font Size 30
• Font Colour Red
• Font Comic Sans
• Font Colour Green Copperplate Gothic Size 36
  Italic

The Quick brown fox jumps over the lazy dog.
6
Sending Messages to Objects

• Bold on
• Italic on
• Bold, Italic off
• Font Size 30
• Font Colour Red
• Font Comic Sans
• Font Colour Green Copperplate Gothic Size 36
  Italic

The Quick brown fox jumps over the lazy dog.
7
Sending Messages to Objects

• Bold on
• Italic on
• Bold, Italic off
• Font Size 30
• Font Colour Red
• Font Comic Sans
• Font Colour Green Copperplate Gothic Size 36
  Italic

The Quick brown fox jumps over the lazy dog.
8
Sending Messages to Objects

• Bold on
• Italic on
• Bold, Italic off
• Font Size 30
• Font Colour Red
• Font Comic Sans
• Font Colour Green Copperplate Gothic Size 36
  Italic

The Quick brown fox jumps over the lazy dog.
9
Sending Messages to Objects

• Bold on
• Italic on
• Bold, Italic off
• Font Size 30
• Font Colour Red
• Font Comic Sans
• Font Colour Green Copperplate Gothic Size 36
  Italic

The Quick brown fox jumps over the lazy dog.
10
Sending Messages to Objects

• Bold on
• Italic on
• Bold, Italic off
• Font Size 30
• Font Colour Red
• Font Comic Sans
• Font Colour Green Copperplate Gothic Size 36
  Italic

The Quick brown fox jumps over the lazy dog.
11
Sending Messages to Objects

• Bold on
• Italic on
• Bold, Italic off
• Font Size 30
• Font Colour Red
• Font Comic Sans
• Font Colour Green Copperplate Gothic Size 36
  Italic

The Quick brown fox jumps over the lazy dog.
12
Sending Messages to Objects

• Each piece of information that an object holds is
  an Attribute.
• The State of an object is the set of current
  values of its Attributes

The Quick brown fox jumps over the lazy dog.
13
Sending Messages to Objects
Text The Quick brown fox jumps over the lazy
dog. Colour Blue Justification Left Font
Type Tahoma Font Size 24 Bold Off Italic Off
The Quick brown fox jumps over the lazy dog.
This blue box describes the state of the text.
The items within it are called the attributes of
the text
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Sending Messages to Objects
MESSAGE Change Colour to Red
Text The Quick brown fox jumps over the lazy
dog. Colour Blue Justification Left Font
Type Tahoma Font Size 24 Bold Off Italic Off
The Quick brown fox jumps over the lazy dog.
The current state of the text.
15
Sending Messages to Objects
MESSAGE Change Colour to Red
Text The Quick brown fox jumps over the lazy
dog. Colour Red Justification Left Font Type
Tahoma Font Size 24 Bold Off Italic Off
The Quick brown fox jumps over the lazy dog.
Text has now changed
The new state of the text.
16
Sending Messages to Objects
The Quick brown fox jumps over the lazy dog.

• The Protocol for an object is the set of messages
  that an object understands.
• Two objects may behave very differently when
  given the same message

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Sending Messages to Objects

• Size 8

The Quick brown fox jumps over the lazy dog.
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Classes of Objects

• Picture Class
• Text Class

The Quick brown fox jumps over the lazy dog.
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Classes of Objects

• Student Class
• Furniture Class

Joanne Brett Abid
Chairs Cupboards Bookcases
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An Object Lesson

• Here is a Table in PowerPoint
• What are its attributes?

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An Object Lesson

• Rows 3
• Columns 3
• Border On
• Border Style Width 1pt
• Cell Contents
• (1,1) , (1,2) X etc.
• Background Clear

22
Modelling the Real World
Computers attempt to model the real world. In
this case, TFs cluttered desk!