Function            isInvisible - is this the invisible program under
                                      Double DOS

  Syntax              boolean isInvisible(void);

  Prototype in        multihk.h

  Remarks             detects if the current program is the invisible
                      program under Double DOS.

  Return value        returns TRUE if the current program is the invisble
                      program under Double DOS, FALSE otherwise.

  See also            DoubleDOSfreeCPU(), DoubleDOSGetVirtual(),
                      DoubleDOSTaskSwitch(), isDoubleDOS()

  Example             #include <ibm.h>

                      main()
                      {
                           printf("This program is ");
                           if (! isInvisible())
                                printf("not ");
                           printf("the invisible program");
                      }