Declaring Variables in FoxPro

ID: Q122907

2.5x 2.60 2.60a 3.00 WINDOWS kbprg

The information in this article applies to:

Microsoft Visual FoxPro for Windows, version 3.0
Microsoft FoxPro for Windows, versions 2.5, 2.5a, 2.5b, 2.6, 2.6a

SUMMARY

Ths article describes how variables are defined (declared) in FoxPro. A variable in FoxPro can have one of three attributes: Public, Private, or Hidden.

MORE INFORMATION

Public Variables

Public variables, also known as global variables, are variables that may be used and modified by any FoxPro program and any of its sub-programs for the duration of the FoxPro session or until the variable is cleared from memory.

Public variables are declared in one of two ways:

1. Create a variable in the Command window. Any variable created in the

   Command window is automatically declared public. For example, from the
   Command window, type X=1000. The variable X is now public to all
   applications.

2. Within a program, declare a variable as public by using the PUBLIC

   command. In all programs, you must declare the variable as public before
   assigning it a value, as in this example code:

   PUBLIC var1
   var1=1000

Private Variables

Private variables are declared within programs or procedures and can be used and manipulated within that program or procedure and any of its sub-programs.

Private variables are declared one of three ways:

1. Create a variable inside a program or procedure without declaring is as

   public. The variable then becomes private to the program or procedure in
   which it is declared.

   For example, in the program MYPRG.PRG, declare var2 as private with
   this command:

      var2=2500

   Now var2 is declared as private to MYPRG.PRG. It is available to all
   procedures called by MYPRG.PRG.

2. Include the variable on a PARAMETERS statement. This automatically

   causes the variable to become private to that program or procedure.

3. Use the PRIVATE command on variables declared previously. This makes

   the previously declared variable and its contents hidden. The new
   private variable becomes private to the current program or procedure.
   The PRIVATE command does not initially declare anything, a variable must
   already exist before PRIVATE can be used on it successfully.

Hidden Variables

Variables may not be declared hidden, but variables that were previously declared as Public or Private may become hidden. By hiding variables created in higher programs, you can enable variables of the same name to be manipulated in the current program without affecting the values of the hidden variables.

Once the program or procedure containing the private variables completes execution, all memory variables and arrays that were subsequently hidden are again available.

Variables are hidden in one of two ways:

1. If a variable has already been declared, use the PRIVATE command

   followed by the variable name to hide the existing variable and create
   a new PRIVATE variable.

2. Use a variable of the same name in a PARAMETERS statement. If a newly

   declared variable shares the same name as a variable previously
   declared, the previously declared variable becomes hidden and a new
   private variable is created for the current program or procedure.

To check the status of a variable, use the DISPLAY MEMORY command. DISPLAY MEMORY provides information about user-defined variables -- whether they are public, private, or hidden, and where (which program or procedure) they were declared.

REFERENCES

Language Reference, version 2.5 pages L3-751, L3-764

Additional reference words: VFoxWin 3.00 FoxWin 2.50 2.50a 2.50b 2.60 2.60a KBCategory: kbprg KBSubcategory: FxprgGeneral

Keywords          : FxprgGeneral 
Version           : 2.5x 2.60 2.60a 3.00
Platform          : WINDOWS