DiskFree()

         Returns the free space of a disk

    Syntax:

         DiskFree( nDisk ) -> nFree

         nDisk : 0 -> default disk
                 1 -> A:
                 2 -> B:
                 3 -> C:
                 ...

    Description:

         Returns the free space of a specified disk

    Return:

         The free space.

    Example:

         ? DiskSize( 0 )        // Disk Capacity
         ? DiskFree( 0 )        // Disk Free