This article originally appeared in TidBITS on 1995-01-23 at 12:00 p.m.
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Image is Everything: ShrinkWrap 1.2

by Geoff Duncan

Anyone who's dealt with floppy disk images knows what a pain they can be. The idea behind a disk image is simple enough: instead of distributing or storing a floppy disk as a physical object, you store it as a file on a larger disk. Admittedly, back in the days of the 128K Macintosh (which came with a single 400K floppy disk drive), this wasn't much of an issue. But as hard drives became commonplace and capacities increased, the idea of storing floppy disks as images became more practical and more necessary. Floppy disks are still one of the principle ways in which software and documents are distributed - after all, nearly every Macintosh has a floppy drive, but the same can't be said of CD-ROM drives, networks, or modems. As a result, people frequently use disk images to back up application disks, to store or send exact copies of floppies online, or (with compression) to pack a few 800K disk images onto a single high-density floppy.

DiskCopy, MountImage, and MungeImage -- For years, images of floppy disks have been hard to deal with and difficult to manage. In the beginning, there was DiskCopy, a utility from Apple that let you read and write floppy images. Using DiskCopy, you could store a floppy on your hard disk as a file, then read that file back out to a floppy disk any time you wanted. (DART is another Apple utility that performs similar functions.) Although DiskCopy is a reliable, bare-bones way to handle floppy images, it leaves a lot to be desired. For instance, to look at or use the contents of an image file, you had to find a floppy disk, copy the image file to it, and then pop the floppy disk back into your drive in order to see the files on it - a major nuisance. But DiskCopy is useful, and Apple continues to distribute system software and software updates in DiskCopy format. dart-153.hqx

Later, Apple introduced MountImage, a control panel that lets you mount a DiskCopy image on your desktop as if it were a real disk. This was a nice step forward: finally the floppy disk itself had been eliminated from the equation, and you could peruse and change the contents of a floppy disk image without having to mess around with a physical floppy disk. Unfortunately, MountImage suffers from a major bug that Apple has been open about: if your original disk image file was fragmented (stored in more than one piece) on your hard disk, MountImage can lose or destroy data in that image and/or other files.

Roger Bates (author of DiskDup+) has offered a safe alternative to MountImage for years, but unfortunately it's not widely available or distributable (it's only available if you pay your shareware fee). Eventually, in mid 1994, the inimitable Peter Lewis and Quinn staged a rescue when they introduced MungeImage, a freeware replacement for MountImage. Peter and Quinn implemented MungeImage as a drag-and-drop application that didn't have extensions conflicts or suffer from MountImage's file fragmentation problem, but MungeImage has virtually no interface and only deals with DiskCopy (and later DART) images. Because other applications do their own flavors of disk images (DiskDup+, DropDisk, Norton's Floppier, and MacTools' FastCopy to name a few), MountImage doesn't provide a one-stop disk image utility solution. disk-dup-plus-25.hqx munge-image-120.hqx

Enter ShrinkWrap -- Now, you have to understand: Chad Magendanz lives for disk images. He has waking dreams of row upon row of 230 MB magneto-optical cartridges lining his home office, all of them filled with backup images of all-too-vulnerable floppy disks. Although pleased as punch about his MO drive, he found the disk image situation in 1994 to be intolerable. Simply speaking, it was a ton of trouble to deal with images, even with MungeImage. Not being afraid of drivers or assembly language, Chad decided to do something about the sorry state of affairs. So ShrinkWrap was born.

Chad based early versions of ShrinkWrap on Peter and Quinn's MungeImage driver and the germ of MungeImage's drag and drop application interface. However, ShrinkWrap also took a hint from Aladdin's StuffIt Expander and DropStuff utilities, adding power and flexibility to its drag and drop capabilities. To mount disk image files, just drag them to the ShrinkWrap icon: like magic, floppies appear on your desktop. To make image files from disks, drag those disks to ShrinkWrap's icon. Voila, image files materialize. ShrinkWrap is also very careful with data; it generates and confirms checksums of disk images for all formats it supports.

But there were still problems. The MungeImage driver used by ShrinkWrap mounted disk images in RAM. This meant that if you wanted to mount a dozen disk images simultaneously (say, to install a major application), you had to have enough free RAM to hold a dozen disk images. This was a big problem for owners of low-end (and even mid-range) machines.

ShrinkWrap 1.2 addresses these issues and more: stuffit-expander-352.hqx drop-stuff-with-ee-352.hqx

Okay - so not everyone deals with disk images every day. In fact, many Macintosh users may never deal with disk images at all. But if you've ever wondered what to do with system updates issued by Apple or if there are reliable ways to back up your original floppy disks from commercial applications or other sources, ShrinkWrap makes the world much simpler. If that doesn't convince you, the ability to create instant RAM disks should appeal to anyone doing graphics work or requiring rapid file access. To be fair, ShrinkWrap has a few bugs (including a crashing problem with MODE32), but for the most part these problems are innocuous - they don't interfere with the majority of ShrinkWrap's uses. Finally, ShrinkWrap is freeware. Just download and enjoy. shrink-wrap-12.hqx