Practical Programming COMP153-06S Lecture 3: Making Decisions.
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Transcript of Practical Programming COMP153-06S Lecture 3: Making Decisions.
![Page 1: Practical Programming COMP153-06S Lecture 3: Making Decisions.](https://reader036.fdocuments.in/reader036/viewer/2022070411/56649f4e5503460f94c6f743/html5/thumbnails/1.jpg)
Practical ProgrammingCOMP153-06S
Lecture 3: Making Decisions
![Page 2: Practical Programming COMP153-06S Lecture 3: Making Decisions.](https://reader036.fdocuments.in/reader036/viewer/2022070411/56649f4e5503460f94c6f743/html5/thumbnails/2.jpg)
Administration
• We are doing Lab 2– MSDN available from CS office– Labs and Lectures are available in the
lab and on the web– Try to finish by Friday (20th)
• You should have had Lab 1 verified by today, or at least by the end of this week
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Programming So Far
• First: Controls, Properties, Events
• Second: Types and Arithmetic
• The test tutorial had a simple calculator which would have been more useful if we could have supplied an operation as well as 2 numbers. That is today’s topic.
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Today – Making Decisions
• Computer can compare and branch
• In VB .NET– The If statement– The Select Case statement
• New type – Boolean (true or false)– Eg: enabled, visible properties
• The checkbox control allows people to make decisions – message box for popping up a window
![Page 5: Practical Programming COMP153-06S Lecture 3: Making Decisions.](https://reader036.fdocuments.in/reader036/viewer/2022070411/56649f4e5503460f94c6f743/html5/thumbnails/5.jpg)
The If statement
If condition Then
statements
ElseIf condition Then
statements
Else
statements
End If
Condition: either a Boolean property or a comparision (with and / or / not)
Statements: any VB .NET statements
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Eg: Setting background
If condition Then
statements
Else
statements
End If
If (YellowCheckBox.Checked) Then
ActiveForm.BackColor = Color.Yellow
Else
ActiveForm.BackColor = SystemColors.Control
End If
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Calculator
If (TextBox3.Text = "+") Then
Label4.Text = Str(Val(TextBox1.Text) + Val(TextBox2.Text))
ElseIf (TextBox3.Text = "-") Then
Label4.Text = Str(Val(TextBox1.Text) - Val(TextBox2.Text))
ElseIf (etc.)
End If
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Tax rates
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Tax rates (2)
• http://www.ird.govt.nz/income-tax-individual/itaxsalaryandwage-incometaxrates.html
• Up to $38,000 19.5 cents/dollar• 38,001 – 60,000 33 cents/dollar• Over 60,000 45 cents/dollar
If (IncomeTextBox.Text <= 38000) Then TaxLabel.Text = IncomeTextBox.Text * 19.5 /
100ElseIf (IncomeTextBox.Text <= 60000) Then TaxLabel.Text = 7410 + (IncomeTextBox.Text –
38000) * 33 / 100Else TaxLabel.Text = 7410 + 7260 +
(IncomeTextBox.Text - 60000) * 39 / 100End If• Comparison with strings is sort order
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The Select Case statement
Select Case expression
Case value
statements
Case value
statements
Case Else
statements
End Select
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Fruit prices
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Fruit prices (2)
Select Case ItemTextBox.Text Case 1 PriceLabel.Text = WeightTextBox.Text * 3.99 Case 2 PriceLabel.Text = WeightTextBox.Text * 5.5 Case 3 PriceLabel.Text = WeightTextBox.Text * 6.0 Case Else
MessageBox.Show(“Please Enter 1, 2 or 3”)End Select
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Calculator (2)
Select Case (TextBox3.Text)
Case "+"
Label4.Text = Str(Val(TextBox1.Text) + Val(TextBox2.Text))
Case "-"
Label4.Text = Str(Val(TextBox1.Text) - Val(TextBox2.Text))
Case “*”
Label4.Text = Str(Val(TextBox1.Text) * Val(TextBox2.Text))
Case “/”
Label4.Text = Str(Val(TextBox1.Text) / Val(TextBox2.Text))
Case “^”
Label4.Text = Str(Val(TextBox1.Text) ^ Val(TextBox2.Text))
Case Else
Label4.Text = “You must use on of (*,+,-,/,^)”
End Select
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Case is clever (first variable)
• Case 1, 3, 5• Case 1 To 10• Case 1 To 4, 7 To 9, 11, 13
Dim Number As Integer = 8
Select Number ' Evaluate Number. Case 1 To 5 ' Number between 1 and 5, inclusive. MessageBox.Show("Between 1 and 5") Case 6, 7, 8 ' Number between 6 and 8. MessageBox.Show("Between 6 and 8") Case 9 To 10 ' Number is 9 or 10. MessageBox.Show("Greater than 8") Case Else ' Other values. MessageBox.Show("Not between 1 and 10")End Select
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THE END
of the lecture