Saturday, January 01, 2005

Macs and disks-on-key

A couple of people told me about problems transferring files between two Macs using a disk-on-key. It being a longtime article of faith of mine that only Microsoft would be capable of making a computer incompatible with itself, I checked this out myself. It turns out to be a pre-OS X relic.

In Apple's file systems (HFS and HFS+), files can have both a "data fork" and a "resource fork". The data fork speaks for itself: the resource fork could hold virtually any number of "resources", each with its own type (ie., icon, PICT, CODE, menu,...). Non-Mac-centric file systems such as FAT32 and ufs don't know the first thing about resource forks, so only the data fork gets preserved upon copying a file to them.

This is no problem for multiplatform file formats such as Micros**t Word, Excel, Powerpoint, GIF, JPEG, PDF,... --- these formats do not have resource forks so they can be copied over as is. However, the Mac-centric file formats of some older Mac-only applications (e.g., Nisus or Kaleidagraph) almost invariably exploited the capabilities of the resource fork.

The answer for such files is: make an archive of them (using DropStuff or the "Make Archive" command in the Finder), copy the resulting .sit or .zip archive via the disk-on-key, and then unpack the archive.