DOCUMENT:Q133740  15-FEB-2000  [foxpro]
TITLE   :Null Value (.NULL.) Is a Marker - Not a Data Type
PRODUCT :Microsoft FoxPro
PROD/VER:WINDOWS:3.0
OPER/SYS:
KEYWORDS:

======================================================================
-------------------------------------------------------------------------------
The information in this article applies to:

 - Microsoft Visual FoxPro for Windows, version 3.0 
-------------------------------------------------------------------------------

SUMMARY
=======

The null value (.NULL.) is not an actual value, it is a marker that denotes that
a memory variable or a field value is missing or unknown. If .NULL. is assigned
to a field or a variable, the field or variable's data type is not changed, but
the value is changed to NULL.

MORE INFORMATION
================

Steps to Demonstration Behavior
-------------------------------

The .NULL. value can be assigned to variables that are numeric or character as
demonstrated by these steps:

1. From the Command window, issue these commands:

      nMyvariable=200        && and press ENTER
      ? TYPE("nMyvariable")  && and press ENTER
      ? nMyvariable

   The N is displayed for nMyvariable denoting a variable of numeric type.

2. To assign a null value (.NULL.) to nMyvariable, issue the following commands
   in the Command window:

      store .NULL. to nMyvariable        && and press ENTER
      ? TYPE("nMyvariable")              && and press ENTER
      ? nMyvariable                      && and press ENTER

   The value N is displayed followed by .NULL.; the type of the variable did not
   change but the value did.

3. To assign a character string to the variable and check the variable type,
   issue the following commands in the Command window:

      cMyvariable="This is a String"     && and press ENTER
      ? cMyvariable                      && and press ENTER

   The screen displays the string "This is a String."

4. Issue the following command in the Command window:

      ? TYPE("cMyvariable")              && and press ENTER

   The screen displays C denoting a character type.

5. Issue the following commands in the Command window:

      STORE .NULL. TO cMyvariable        && and press ENTER
      ?TYPE("cMyvariable")               && and press ENTER

   The screen displays C to show that the type has not been changed.

Additional query words: VFoxWin

======================================================================
Keywords          :  
Technology        : kbVFPsearch kbAudDeveloper kbVFP300
Version           : WINDOWS:3.0

=============================================================================

THE INFORMATION PROVIDED IN THE MICROSOFT KNOWLEDGE BASE IS
PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND.  MICROSOFT DISCLAIMS
ALL WARRANTIES, EITHER EXPRESS OR IMPLIED, INCLUDING THE WARRANTIES
OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.  IN NO
EVENT SHALL MICROSOFT CORPORATION OR ITS SUPPLIERS BE LIABLE FOR
ANY DAMAGES WHATSOEVER INCLUDING DIRECT, INDIRECT, INCIDENTAL,
CONSEQUENTIAL, LOSS OF BUSINESS PROFITS OR SPECIAL DAMAGES, EVEN IF
MICROSOFT CORPORATION OR ITS SUPPLIERS HAVE BEEN ADVISED OF THE
POSSIBILITY OF SUCH DAMAGES.  SOME STATES DO NOT ALLOW THE EXCLUSION
OR LIMITATION OF LIABILITY FOR CONSEQUENTIAL OR INCIDENTAL DAMAGES
SO THE FOREGOING LIMITATION MAY NOT APPLY.

Copyright Microsoft Corporation 2000.