Function IsPrime(TestNumber As Long) As Boolean
     Dim Count As Long
     Dim HalfNumber As Long
     HalfNumber = TestNumber / 2 + 1
     For Count = 2 To HalfNumber
         If (TestNumber Mod Count) = 0 Then
            IsPrime = False
            Exit Function
         End If
     Next
     IsPrime = True
 End Function
 
 Private Sub Command1_Click()
 Dim Number As Long
 Dim MyTime As Variant
 Dim Count As Long
 Count = Val(Text1.Text)
 MyTime = Timer
 For Number = 1 To Count
     IsPrime (Number)
 Next Number
 MsgBox (Timer - MyTime) & "seconds"
 End Sub

Figure 2   IsPrime Ported to C

 #include <STDIO.H>
 #include <WINDOWS.H>
 
 unsigned char IsPrime(unsigned long TestNumber);
 unsigned long NextNumber, StartTime, CurrTime, NoPrime;
 
 void main(int argc, char **argv)
    {
    StartTime = GetTickCount();
    for(NextNumber = 1; NextNumber <= 50000; NextNumber++)
       IsPrime(NextNumber);
    CurrTime = (GetTickCount() - StartTime) / 1000;
    printf("Time = %l seconds\n", CurrTime);
    }
 /* Tests for prime numbers */
 unsigned char IsPrime(unsigned long TestNumber)
    {
    unsigned long count;
    unsigned long HalfNumber = TestNumber / 2 + 1;
    for(count = 2; count < HalfNumber; count++)
        if(TestNumber % count == 0)
            return FALSE;
    return TRUE;
    }

Figure 3   Code Execution Times

Code Type	Elapsed time (in seconds)	Percentage of p-code speed
Within the Visual Basic environment	134.63	79%
Compiled p-code	106.72	100%
Compiled native code	40.15	265%
C program	35.12	305%

Figure 4   UserControl Properties

Property	Description
AccessKeys	String containing all mnemonics for this control
Alignable	Determines whether the UserControl can be aligned in its container
Ambient	Returns the container object that has ambient property values
CanGetFocus	Determines whether the UserControl can have the focus
ContainedControls	Returns the set of controls contained within the UserControl
ControlContainer	Determines whether the UserControl can act as a container for other controls at design time
DefaultCancel	Determines whether the UserControl behaves like a button
EditAtDesignTime	Determines if the UserControl will have an Edit verb on the menu
EventsFrozen	Returns whether events on the control are frozen
Extender	Returns the container object that has extended properties or methods for the control
ForwardFocus	Determines whether the UserControl behaves like a label
Hyperlink	Returns a Hyperlink object used for browser-style navigation
InvisibleAtRuntime	Determines whether the UserControl is invisible at runtime
ParentControls	Returns the set of controls contained by the UserControl's parent
PropertyPages	Determines the names of property pages for the UserControl
Public	Determines whether the control is accessible to other clients
ToolboxBitmap	References a graphic that represents the UserControl in the toolbox

Figure 5   UserControl Methods

Method	Description
AsyncRead	Asynchronously read data from a URL
CancelAsyncRead	Cancel an asynchronous read
CanPropertyChange	Asks the container of the UserControl if a control property may be changed
PropertyChanged	Signals that a property of the UserControl changed

Figure 6   UserControl Events

Event	Description
AccessKeyPress	Occurs when the user hits a mnemonic that the UserControl exposes
AmbientChanged	Occurs when an ambient value was changed by the container of a UserControl
AsyncReadComplete	Occurs when the specified property is done loading
EnterFocus, ExitFocus	Occurs when the UserControl is UIActivated or UIDeactivated (tabbed into or tabbed away from)
Show, Hide	Occurs when the UserControl is shown/hidden.
InitProperties	Occurs the first time a UserControl is created
ReadProperties	Occurs when a UserControl is asked to read its data from a file
WriteProperties	Occurs when a UserControl is asked to write its data to a file

Figure 7   Ambient Properties

Ambient Property	Description
DisplayAsDefault	Tells you whether your control is the default button for the container. If your control is the default, then pressing the Enter key is equivalent to clicking on your control. Controls that are the default (DisplayAsDefault = True) should draw an extra-heavy border that identifies the default button to the user.
DisplayName	The name of the particular instance of the control. It should be used when raising errors at design time so the developer who receives the error can identify the control instance causing the error.
ForeColor, BackColor, and Font	Hints your control can use to make its appearance match that of the container. For example, in the InitProperties event fired whenever an instance of your control is first placed in a container, it is highly recommended to set your control's ForeColor, BackColor, and Font properties to the values supplied by the ambient properties.
TextAlign	Tells the control how the client site would like the control to arrange the text it displays. If the value of the property is 0, the control should obey "general" alignment principles: text aligned to left, numbers to right. A value of 1 means left alignment, 2 means center alignment, 3 means right alignment, and 4 means justification.
LocaleID	Lets the container tell the control in which locale the control should consider itself to be running.
Palette	Provides the current palette of the container.
UserMode	Allows an instance of your control to determine whether it is executing at design time (UserMode = False) or at runtime (UserMode = True).