VCL Examples: Operations

This fundamental application illustrates the use of radio buttons to perform simple arithmetic operations such as the addition, the subtraction, the multiplication and the division.

Practical Learning: Creating Radio Buttons

1. Start a new project with the default form
2. To save it, on the Standard toolbar, click the Save All button
3. Click the Create New Folder button. Type Operations and press Enter twice
4. Click Unit1 to select it. Type Main and press Enter
5. Type Operations as the name of the project and press Enter
6. On the Standard tab of the Component Palette, click the Panel control
7. On the form, click and drag from the top left section to the middle center section
8. On the Object Inspector, click Caption and press Delete to delete the caption of the panel
9. On the Component Palette, double-click the RadioButton control
10. On the Object Inspector, click Caption and type &Addition
11. Click Name and type rdoAddition
12. Move the new radio button to the top section of and inside the panel
13. On the Component Palette, click the Radio Button
14. Click inside the panel
15. Click Name and type rdoSubtraction
16. Click Caption and type &Subtraction
17. In the same way, add another RadioButton control to the panel. Set its Caption to &Multiplication and its Name to rdoMultiplication
18. Add one more RadioButton to the panel
19. Set its Name to rdoDivision and its Caption to &Division
     
    
20. Move the panel to the right section of the form
21. Notice that it moves with its “children”. You will redesign the form as follows:
     
    
22. Add another panel with four labels captioned
    Number &1:
    Number &2:
    ------------------
    Result:
23. Add three Edit controls inside the panel and on the right side of the corresponding labels. These edit boxes will be named edtNumber1, edtNumber2, and edtResult
24. Add another panel to an empty area of the form
25. While the new and last panel is selected, click the Align field. Click its arrow and select alBottom
26. On the form double-click the Addition radio button to access its OnClick event
27. Implement it as follows:
     

    //--------------------------------------------------------------------------- void __fastcall TfrmOperations::rdoAdditionClick(TObject *Sender) { double Num1; double Num2; double Result; if( edtNumber1->Text == "" ) Num1 = 0; else Num1 = StrToFloat(edtNumber1->Text); if( edtNumber2->Text == "" ) Num2 = 0; else Num2 = StrToFloat(edtNumber2->Text); Result = Num1 + Num2; edtResult->Text = Result; } //---------------------------------------------------------------------------

28. Click the arrow on the top section of the Object Inspector and select rdoSubtraction
29. Click the Events tab
30. Double-click the empty box on the right side of OnClick
31. Implement the function just like the Click event of the addition but change the operation as follows:
    Result = Num1 - Num2;
32. On the top combo box of the Object Inspector, select rdoMultiplication
33. Double-click the box of the OnClick field
34. Implement the Click event like the previous two but change the operation as follows:
    Result = Num1 * Num2;
35. In the same way, access the OnClick event for the rdoDivision control and implement it as follows:
     

    //--------------------------------------------------------------------------- void __fastcall TfrmOperations::rdoDivisionClick(TObject *Sender) { double Num1; double Num2; double Result; if( edtNumber1->Text == "" ) Num1 = 0; else Num1 = StrToFloat(edtNumber1->Text); if( edtNumber2->Text == "" ) { MessageBox(NULL, "The Number 2 Edit Box should not be empty", "Algebraic Operations", MB_OK); edtNumber2->SetFocus(); } else if( edtNumber2->Text == 0 ) { MessageBox(0, "Cannot divide by zero", "Algebraic Operations", MB_OK); edtNumber2->SetFocus(); } else { Num2 = StrToFloat(edtNumber2->Text); Result = Num1 / Num2; edtResult->Text = Result; } } //---------------------------------------------------------------------------

36. To display the form, press F12
37. Double-click the panel on the bottom section of the form to access its OnClick event and implement it as follows:
     

    //--------------------------------------------------------------------------- void __fastcall TfrmOperations::Panel3Click(Tobject *Sender) { Close(); } //---------------------------------------------------------------------------

38. To test the form, press F9
39. After using it, close the form and save your project