Calculator Processing
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This document provides instructions for adding additional functionality to a calculator application. It begins by describing how to start a new project and import starter code files. It then provides code snippets to add square root, percentage, and decimal point buttons. Global variables and logic are added to track decimal points and prevent multiple entries. Finally, it describes modifying existing code to support multiple math operations by tracking the selected operation, and provides instructions to add minus, multiply, and divide buttons, handling divide by zero errors.
Calculator Processing
- 2. Start freshStart VS 2005 and Create a new project: Calculator_IT1C_xxChoose appropriate directory and remember its pathExit VS 2005Unzip start_cal.zip: Form1.vb and Form1.Designer.vbUse File explorer to replace the two newly created project files in Calculator_IT1C_xx
- 3. ButtonSqrt_ClickDouble click on the button for Sqrt to generate the ButtonSqrt_Click subroutineCopy the codes from ButtonEqual_ClickModify the following line to use Math.Sqrt total = total + x total = Math.Sqrt(x)
- 4. ButtonPercent_ClickDouble click on the button for % to generate the ButtonPercent_Click subroutineCopy the codes from ButtonEqual_ClickModify the following line to use Math.Sqrt total = total + x total = x / 100
- 5. DotPrivate Sub ButtonDot_Click‘ Copy the codes from Button0‘ Replace “0” with “.” Dim existingString As String = TextBox1.Text If existingString <> "" Then TextBox1.Text = existingString & "0" End IfEnd Sub“.”
- 6. Testing1.5 OK0.5 NG => How?
- 7. DotPrivate Sub ButtonDot_Click‘ Add else condition‘ to add “0.” Dim existingString As String = TextBox1.Text If existingString <> "" Then TextBox1.Text = existingString & “.” End IfEnd Sub ElseTextBox1.Text = existingString & “0.” End IfEnd Sub
- 8. Testing1.5 OK0.5 OK1.5.5. => should not allow – How?
- 9. How to stop “1.5.5.”?We need to use a global variable to track if “.” has been set Then add additional codes in ButtonDot to check this variable
- 10. DotGlobal variable:Public Class Form1Dim isDotted As Boolean = False
- 11. DotPrivate Sub ButtonDot_Click‘ Add Condition to check for isDottedDim existingString As String = TextBox1.TextIf existingString <> "" ThenTextBox1.Text = existingString & “.” ElseTextBox1.Text = existingString & “0.” End IfEnd SubIf isDotted = False ThenisDotted= True ‘ Set isDotted to True End IfEnd Sub
- 12. Testing1.5 OK0.5 OK1.5.5. OK1.5 Clear 1.5 => NG - How?
- 13. DotPrivate Sub ButtonClear_Click : : ‘ Reset isDotted to FalseisDotted = FalseEnd Sub
- 14. Testing1.5 OK0.5 OK1.5.5. OK1.5 Clear 1.5 OK1.5 + 1.5 => NG – How?
- 15. DotPrivate Sub ButtonPlus_Click : : ‘ Reset isDotted to FalseisDotted = FalseEnd Sub
- 16. Testing1.5 OK0.5 OK1.5.5. OK1.5 Clear 1.5 OK1.5 + 1.5 OKAnymore cases?
- 17. Minus, Multiply and DivideBefore we proceed to add the processing for Minus, Multiply and Divide,we need to modify the current processing for Plus and Equal
- 18. Modify Plus and EqualPrivate Sub ButtonPlus_Click : : total = total + x :End Subtotal = x ‘ Now, Plus can only be ‘ pressed once.
- 19. Modify Plus and EqualGlobal variable:Public Class Form1 Dim whatFunction As String = “None”
- 20. Modify Plus and EqualPrivate Sub ButtonPlus_Click : :whatFunction = “Plus”End Sub
- 21. Modify Plus and EqualPrivate Sub ButtonEqual_Click : : total = total + x :End SubSelect Case whatFunctionCase “Plus” total = total + xEnd SelectCase “Minus”
- 22. Add Minus, Multiply and DivideComplete the processing for minus, multiply and divide.Take care of divide by zero error with if then else statementDo testingand debugging to take care of other errors