You can also use SYS(16,0). Like this.

* Setup debugging environment.
IF ! ".EXE" $ SYS(16,0) AND FILE("D:\DebugVFP.PRG")
   DO ("D:\DebugVFP.PRG") WITH "INIT"
ENDIF

>This has come up a number of times, and I'm wondering if there is a convenient way to tell whether the application is being run from the VFP development environment of from and executable. The idea is to allow functinality for developers that is not available for customers (using the EXE).
>
>I have a work-around for this - just check for the existence of one of the .prg files that are not distributed with the executable. Still, it seems that maybe there is a better way.