How VB  Can Determine If a Specific Windows Program Is Running

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This article is reprinted from the Microsoft Knowledge Base.  To view the article, maximize your help window.  This information applies to Visual Basic for Windows, versions 2.0 and 3.0.

To determine if a specific program is running, call the Windows API

function FindWindow. FindWindow returns the handle of the window whose

class is given by the lpClassname parameter and whose window name, or

caption, is given by the lpCaption parameter. If the returned value is

zero, the application is not running.

More Information:

By calling FindWindow with a combination of a specific program's class

name and/or the title bar caption, your program can determine whether

that specific program is running.

When an application is started from the Program Manager, it registers

the class name of the form. The window class provides information

about the name, attributes, and resources required by your form. All

Visual Basic forms have a class name of "ThunderForm." You can

determine the class name of an application by using SPY.EXE that comes

with the Microsoft Windows Software Development Kit (SDK) version 3.0 or 3.1.

If the window has a caption bar title, you can also use the title to

locate the instance of the running application. This caption text is

valid even when the application is minimized to an icon.

Because another instance of your Visual Basic program will have the

same class name and may have the same title bar caption, you must use

dynamic data exchange (DDE) to determine if another instance of your

Visual Basic program is running. (This DDE technique is not shown in

this article).

The following example shows three ways to determine if the Windows

Calculator is running. To create the program, do the following:

1. Run Visual Basic, or from the File menu, select New Project

   (ALT, F, N) if Visual Basic is already running.  Form1 will be

   created by default.

2. Declare the Windows API function FindWindow in the Global-

   Declarations section of Form1. The variables are declared

   as "Any" because you can pass either a pointer to a string, or a NULL

   (or 0&) value. You are responsible for passing the correct

   variable type. Note that the Declare statement should be entered on

   just one line:

   Declare Function FindWindow% Lib "user" (ByVal lpClassName As Any,

                                            ByVal lpCaption As Any)

3. Add the following code to the form's Click event. This example

   demonstrates how you can find the instance of the application with a

   combination of the class name and/or the window's caption. In this

   example, the application will find an instance of the Windows

   calculator (CALC.EXE).

Sub Form_Click ()

   lpClassName$ = "SciCalc"

   lpCaption$ = "Calculator"

   Print "Handle = ";FindWindow(lpClassName$, 0&)

   Print "Handle = ";FindWindow(0&, lpCaption$)

   Print "Handle = ";FindWindow(lpClassName$,lpCaption$)

End Sub

4. Run this program with CALC.EXE running and without CALC.EXE

   running. If CALC.EXE is running, your application will print an

   arbitrary handle. If CALC.EXE is not running, your application will

   print zero as the handle.

Below are some class names of applications that are shipped with

Windows:

Class Name         Application

-----------        -----------

SciCalc            CALC.EXE

CalWndMain         CALENDAR.EXE

Cardfile           CARDFILE.EXE

Clipboard          CLIPBOARD.EXE

Clock              CLOCK.EXE

CtlPanelClass      CONTROL.EXE

XLMain             EXCEL.EXE

Session            MS-DOS.EXE

Notepad            NOTEPAD.EXE

pbParent           PBRUSH.EXE

Pif                PIFEDIT.EXE

PrintManager       PRINTMAN.EXE

Progman            PROGMAN.EXE   (Windows Program manager)

Recorder           RECORDER.EXE

Reversi            REVERSI.EXE

#32770             SETUP.EXE

Solitaire          SOL.EXE

Terminal           TERMINAL.EXE

WFS_Frame          WINFILE.EXE

MW_WINHELP         WINHELP.EXE

#32770             WINVER.EXE

OpusApp            WINWORD.EXE

MSWRITE_MENU       WRITE.EXE