FAQ: Visual Basic Programming in Visual Basic 4.0

• Microsoft Visual Basic Standard, Professional, and Enterprise Editions, 16-bit and 32-bit, for Windows, version 4.0

SUMMARY

This article covers some of the most Frequently Asked Questions (FAQs) about technical issues for Microsoft Visual Basic for Windows. You can find this and other FAQ articles by querying on the keyword "FAQ." You can find additional general references in the Microsoft Knowledge Base by searching on "article list."

MORE INFORMATION

1. Q. I'm getting error #6 "Overflow." What's wrong?
   
   A. The most common cause of an overflow error is exceeding the upper or lower bounds of either the type of a data variable or the limits of the property for an object.
   
   Query on "Data Types" in the Visual Basic Online Help to determine the upper and lower bounds for various data types, such as integer or long.
   
   Other causes of this error are documented in the following Knowledge Base articles.
   
   Q129803 : Variable Coercion Rules in Visual Basic Version 4.0
   
   Q129709 : PRB: Overflow Error at Run Time w/Byte Type Counter in For Loop



2. Q. How can you determine if a file exists on a drive?
   
   A. Use the Dir function. The Dir function returns the name of a file or directory that matches a specified pattern or file attribute or the volume label of a drive. For more information on the Dir function, query on "Dir" in the Visual Basic Online Help, or see the following article in the Microsoft Knowledge Base:
   
   Q112674 : How to Determine If a File Exists by Using DIR$



3. Q. Now that I found the file, how do I delete it?
   
   A. Use the Kill statement. The Kill statement deletes the specified pathname and file from a disk. If you try to use the Kill statement to delete an open file, an error occurs. To delete directories, use the RmDir statement.
   
   For more information on the Kill statement, query on "Kill" in the Visual Basic Online Help.



4. Q. I'm getting "Illegal Function Call." What's wrong?
   
   A. The following are some situations that can generate an Illegal

   
         Function call:
   
         CAUSE:      Function does not exist in the program.
         RESOLUTION: Make sure that the function exists in the program and
                     that the function is accessible to the form or procedure
                     calling the function. Place the function in a module to
                     allow access by any part of your program. Make sure that
                     the function name in the calling procedure matches the
                     name of the function.
   
         CAUSE:      Wrong number of parameters passed to the function.
         RESOLUTION: Check that the correct number of parameters is passed to
                     the function.
   
         CAUSE:      Wrong parameter type is passed to the function.
         RESOLUTION: Check that the parameter being passed to the function is
                     the type that the function expects. For example, passing
                     an integer parameter to a function expecting a string
                     results in this error.
   
         CAUSE:      Byte range for a character exceeded.
         RESOLUTION: Check that the byte value of a character is between 0 and
                     255. For example, if you add 50 to the extended-ASCII
                     character CHR(230) and assign it to a string in Visual
                     Basic, the result is an "Illegal function call" error.
    

   Another cause of this error is documented in the following Knowledge Base article:
   
   Q142937 : How to Prevent Multiple Instances of a VB Application



5. Q. How can I be sure that all my forms are unloaded correctly?
   
   A. Use the following code in the Unload event of the form that has triggered your applications exit:

   
         Dim i as integer
         While forms.Count > 1
   
            ' Find first form besides "me" to unload
            i = 0
            While forms(i).Caption = Me.Caption
               i = i + 1
            Wend
            Unload forms(i)
         Wend
   
         ' Last thing to be done...
         Unload Me
         End
    




6. Q. Where are the corrections to the manuals listed?
   
   A. Get out your red pen and query the Knowledge Base using the "vb4win" and "kbdocerr" keywords for a list of documentation errors.



7. Q. How do I make my Visual Basic program Windows 95 logo compliant?
   
   A. Request a pre-testing kit from the Windows Logo Department from the following sources:

   
         E-mail:   winlogo@microsoft.com
         Fax:      (206) 936-7329, Attn: Windows Logo Department
         Phone:    (206) 936-2880
         Mail:     Microsoft Corporation
                   Attn: Windows Logo Department
                   Bldg. 20
                   Redmond, WA 98052- 6399
    

   This kit provides all the information about requirements to display the Windows 95 logo on your program. For more information on the Windows Logo Program, see the following web site:
   
   http://www.microsoft.com/windows/winlogo/

Additional query words: 4.00 vb4win vb4all faq fax back

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Last Reviewed: June 3, 1999