How Your Data Compression Options Stack Up

If you like to buy software, especially Windows software, sooner or later you will face the problem of how to get more data storage space for your computer.

Most computers sold today are equipped with high-capacity hard disks--typically 80 to 250 megabytes--but software can eat up storage space in a hurry. Adding a fax modem and a scanner to your system places big demands on disk storage space, since these devices create such large graphics files.

Stacker 3.0 for Windows and DOS, $149, from Stac Electronics in Carlsbad, is the first disk compression program designed especially for Windows 3.1. It is the third version of Stacker, the program that originated this category of software and still the largest seller. (Stacker versions for Macintosh and OS/2 are due out shortly.)

However, firms that specialize in disk compression software for DOS face a clouded future. Microsoft plans to offer built-in disk compression software with its next version of the MS-DOS operating system.

Microsoft says it is using a public domain compression formula, but Stac Electronics has filed a lawsuit in federal court in Los Angeles, accusing the Bellevue, Wash.-based software giant of infringing its disk compression patents. Stac alleged that Microsoft discussed incorporating Stacker in MS-DOS 6.0., but wasn’t willing to pay any royalties.

Microsoft spokesman Collins Hemingway said Microsoft did “offer money” to the Carlsbad firm for Stacker, “but we couldn’t reach an agreement.” He declined further comment on the case.

Hemingway said Microsoft plans to release MS-DOS 6.0 with disk compression this spring. The compression system combines technology Microsoft licensed from other companies with its own development, he said.

If the new compression feature is as fast and efficient as Stacker, it is doubtful that people will want to buy both the Microsoft product and Stacker. But for the time being--and for as long as you use MS-DOS 5.0 or an earlier version--Stacker 3.0 for Windows and DOS is worth considering.

The technology that enables program and data files to be compressed into, typically, half their normal size is safe and well-proven. It is possible because computer files tend to contain various redundant patterns that can be summarized with absolute accuracy.

Stacker creates a single huge file on the hard disk in which it places compressed versions of all of your files. It’s quite difficult to accidentally erase the master file, so that shouldn’t be a concern.

Stacker 3.0 is compatible with disk repair utility software such as SpinRite or Norton Disk Doctor, which some people like to use to try to stave off hard disk failures.

With prior versions of Stacker, it was difficult to remove the program once you had it installed. You had to make a backup copy of all files on diskettes or tape, then reformat the hard disk and recopy the backup versions onto the hard disk. With version 3.0, Stacker now has an “unstack” procedure that restores all of your files to their original form, provided you still have room on the hard disk for all of them in uncompressed form.

Stacker takes away a small amount of computer memory that would otherwise be available for other programs to use. Normally it needs about 40 kilobytes of memory to operate, but there is a way to squeeze it to about 22 kilobytes by tuning your memory usage.

The best time to install Stacker, ironically, is not when your hard disk is nearly full, but when your computer is new and the disk is nearly empty. Ideally, you should partition your hard disk into at least two sections and leave the first one, the one containing DOS, uncompressed.

Make the uncompressed partition big enough to contain a few programs and then you’ll be able to run those programs with Stacker disabled, which gives them access to the largest possible amount of your computer’s memory. Some applications and games need virtually all the memory. Of course, while Stacker was temporarily disabled, you wouldn’t have access to the compressed portion of the disk, so it takes careful planning to determine the optimum way to set things up on your system.