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Tech Tip: Mac/PC Hybrid CD-ROM trick
Published On: December 3, 1999

A CD-ROM is capable of storing up to 650MB of data. A "Mac/ISO Hybrid" CD is a CD-ROM that has been dynamically formatted into two distinct "volumes," a Macintosh (HFS) volume and a PC (ISO 9660) volume. A CD-ROM constructed in this way is capable of being accessed by either platform. A Mac will see and mount the HFS portion of the CD and a PC will see only the ISO portion. For most purposes, 4D Developers should find 650MB more than sufficient storage space to burn their own hybrid "Product CD."

Occasionally, developers may wish to burn and distribute a demo CD. However, what if the datafile you want to include on your demo CD is 400MB in size, or larger... for each platform? How will you fit 800MB+ of data on a 650MB disk? Rather than burning a convenient hybrid CD, it would appear that you will be forced to burn two separate demo CDs, one for each platform.

A technique often used when constructing a Mac/ISO Hybrid CD, is to place all of the cross-platform files on the Macintosh side of the CD-ROM (PDF documents, HTML documents, JPEGs, etc.), and place only aliases to these files on the PC side of the CD-ROM. A distinct advantage in doing this is the considerable potential for saving CD-ROM space (relative of course to how many cross-platform files there are). It is totally transparent to the PC user (while using the CD-ROM) that the "PC" files he's accessing are actually on the Macintosh side of the CD.

You can use this technique to solve the oversize demo database problem, and end up with a single hybrid CD after all. Here's how:

  1. Build the Macintosh side of the CD as you normally would, with one notable exception: rename the datafile exactly how it needs to appear on the PC side. i.e., with a ".4DD" appendage.
  2. On the PC side, create an alias to the Mac datafile (with the .4DD appendage). Finally add the .RSR file that would normally be associated with the .4DD datafile.

Since you are using only one 400MB datafile and simply "sharing" it across platforms, you will be well within the 650MB limit of the CD-ROM.