$SOURCEDIR$ is assigned the value of the drive and the directory on which the installation occurs. Usually the root directory of the floppy disk drive, which has your installation disk in it. This value includes both the disk drive and the directory path.

Common uses include:

  • Passing the location of the original installation disk to an external program invoked with the RunAtExit command.
  • Using variable to remove a file from the installation disk (using the DELETE command) to prevent a second installation.