If you're in HyperCard and you want to check how much space you have left
on your storage volume, type "the diskSpace" (it's not case sensitive) into
the message box. HyperCard (versions 1.x through 2.1x) will display the
total amount of disk space free (in kilobytes) on the active volume.
This script works in all versions of HyperCard up through 2.1.
This article is adapted from the Claris Tech Info database.