1 CC111 Lec9 : Visual Basic Visual Basic (3) Lecture 9.

1CC111 Lec9 : Visual Basic

Visual Basic (3)

Lecture 9


Controlling your Application

• Sequence

• Selection– If...Then...Else statement– Select Case statement

• Repititon – For...Next Loop statement– For Each...Next statement– Do Loops


Selection If..Then..Else

If (condition) Then (statement[s])[ElseIf (condition) Then

(statement[s])][Else (statement[s])]


Selection Application: Convert from Numerical Grade to Letter Grade

•Input: a numeric grade between 0 and 100

•Output: depends on input

Input Output

049 F

5054 D

5559 C-

6064 C

6569 C+

7074 B-

7579 B

8084 B+

8589 A-

9094 A

95100 A+


Selection Application Convert from Numerical Grade to Letter Grade (Form View)

Letter_Grade_Calculator.exe


Selection Application: Convert from Numerical Grade to Letter Grade (Code View)Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click If (ComboBox1.SelectedIndex = 0) Then Label2.Text = "F" End If If (ComboBox1.SelectedIndex = 1) Then Label2.Text = "D" End If If (ComboBox1.SelectedIndex = 2) Then Label2.Text = "C-" End If If (ComboBox1.SelectedIndex = 3) Then Label2.Text = "C" End If If (ComboBox1.SelectedIndex = 4) Then Label2.Text = "C+" End If If (ComboBox1.SelectedIndex = 5) Then Label2.Text = "B-" End If If (ComboBox1.SelectedIndex = 6) Then Label2.Text = "B" End If If (ComboBox1.SelectedIndex = 7) Then Label2.Text = "B+" End If If (ComboBox1.SelectedIndex = 8) Then Label2.Text = "A-" End If If (ComboBox1.SelectedIndex = 9) Then Label2.Text = "A" End If If (ComboBox1.SelectedIndex = 10) Then Label2.Text = "A+" End If

End Sub


Selection Application Convert from Numerical Grade to Letter Grade (Run)


For...Next Loop Structure

For counter = start To end Step incrementstatements

Next counter

WhereCounter is tested to see if less than end.

If so, repeat loop again. If not, go to statement after Next.


Loops Application: Factorial

• Factorial (N)= N*(N-1)*(N-2)……….*(1)


Factorial Flowchart (N>0)


Factorial Application: Form View

Factorial.exe


Factorial Application: Code ViewUsing For..Next Loop

Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click Dim n As Integer Dim m As Integer Dim f As Integer n = Val(TextBox1.Text) f = 1 For m = 1 To n Step 1 f = f * m Next m Label2.Text = "Factorial=" + Str(f) End Sub


Factorial Application: Run


Do While...Loop Structure

Do While conditionstatements

Loop

WhereThe condition is tested, and if true the loop isrepeated.

When the condition is false, the statements are skipped after Loop is executed.



• Factorial (N)= N*(N-1)*(N-2)……….*(1)


Factorial Application: Code ViewUsing Do..While..Loop

Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click Dim n As Integer Dim m As Integer Dim f As Integer n = Val(TextBox1.Text) f = 1 m = 1 Do While m <= n f = f * m m = m + 1 Loop Label2.Text = "Factorial=" + Str(f) End SubEnd Class


Do Until...Loop Structure

Do Until conditionstatements

Loop

WhereThe condition is tested, and if false the loop isrepeated.

When the condition is true, the statements are skipped after Loop is executed.



• Factorial (N)= N*(N-1)*(N-2)……….*(1)


Factorial Application: Code ViewUsing Do..Until..Loop

Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click

Dim n As Integer Dim m As Integer Dim f As Integer n = Val(TextBox1.Text) f = 1 m = 1 Do Until m > n f = f * m m = m + 1 Loop

Label2.Text = "Factorial=" + Str(f) End Sub


Factorial Application: Run

1 CC111 Lec9 : Visual Basic Visual Basic (3) Lecture 9.

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