With a compression program, you can put more files on a disk


July 01, 1991|By Phillip Robinson | Phillip Robinson,Knight-Ridder News Service

One of the most vital jobs of a computer's operating system -- its basic software -- is storing and retrieving information on disks at the request of programs like word processors or spreadsheets.

Unfortunately, neither DOS (the operating system for IBM and compatible personal computers) nor Apple's Macintosh operating system offers data compression, a technique to snip blank areas out of graphics images, cut repeated spaces and characters from text and so on.

While some files can be compressed just a bit, others can be reduced to as little as one-tenth their initial size, letting you put more files on a disk. And the computer stores and retrieves smaller files more quickly.

The disadvantage of compression is that squishing or unsquishing each file takes time and requires extra work from the computer's microprocessor. If you have compression hardware -- a special chip tailored to the task -- you don't notice the delay. But if you depend on a software utility for the work, which is a less-expensive choice, you might.

The practicality of compression depends on your object and patience. If you have huge graphics files that eat up too much disk space, you'll probably be happy enough with a special program that you must call for explicitly, one that squishes them as much as possible.

But if you want to compress everything to make more effective use of your disk space, you'll want a compression program that's automatic yet unobtrusive. These "on-the-fly" programs are available for both DOS and Macintosh computers.

SuperStor (AddStor, (415) 688-0465, $129) adds to any personal computer's DOS operating system. It installs automatically, though it asks you to answer some questions about intimidating terms such as "mounting" a drive. Once it is installed, however, it runs completely automatically. Then it not only compresses and decompresses all files with no more trouble from you, but also it uses the disk more efficiently by decreasing the minimum stored chunk size from 2,048 bytes to 512. (DOS wastes some disk space by insisting on that minimum size.)

My Zenith Data Systems 486-based PC compatible seemed like the perfect candidate for SuperStor. It has a fast processor and a 180-megabyte hard-disk drive. After I installed SuperStor -- which took about 15 minutes -- I had the equivalent of a 340-megabyte hard disk.

After that, I didn't even need to know that SuperStor was in town. I started and ran programs as always, but I had more room to move.

SuperStor also will double the size of a floppy disk (or even of a random-access memory disk). However, I'm a bit less comfortable with that prospect because I want floppies that other PCs can read.

I won't be completely at ease with SuperStor until I've used it for a while and don't find conflicts with my programs. And there are some utilities that it is known not to work with, including some parts of popular packages like PC Tools. But in general, it has everything you could want for simple, automatic compression, from the ability to handle large hard disks (up to 512 megabytes) to fitting its program code into high DOS memory (to keep as much of your 640 kilobytes of main memory free as possible).

SuperDisk! (Alysis, (415) 566-2263, $89) can increase your Macintosh disk space, but it doesn't work in just the same way SuperStor does on the PC.

SuperDisk! is easier to install, largely because Mac software is easier to install than PC stuff. You copy the SuperDisk! program into the Mac's system folder and restart your Mac. Thereafter, any files you name with a ".s" at the end are automatically compressed when out of use and automatically decompressed when needed again. You may also name folders with a ".s" at the end, and then all files within the folders are compressed and decompressed.

The compression is fast. For instance, I compressed a 280K file down to 50K in just four seconds on the relatively slow Mac Portable. You can choose faster or slower compression and tighter (which takes longer) or larger (which is faster) results.

You may assign passwords to compressed files to limit who can decompress them. You can also make "auto-expanding" files, squished files that any Macintosh can decompress, even those without SuperDisk! (The decompression software is built into the squashed file.) This is very handy if you want to send files to other Mac owners (smaller files cost less to send through a modem). I even like SuperDisk!'s cute graphics (like a crushed cola can showing you the compression progress) and thorough on-line help and explanations.

My only beef with SuperDisk! is that compressed files aren't always recognized by their programs. My TouchBase program couldn't find its database file when that file was compressed, so all of my phone numbers and addresses were out of reach.

In other words, you cannot just compress your entire disk, as SuperStor allows you to do on the PC.

Both SuperStor and SuperDisk! are inexpensive ways to get a lot more disk space. They're both easy to use, too, though with a few rough spots. And they're much faster than I expected -- fast enough to prevent bothersome delays (though I didn't test SuperStor's pace on a slow PC like the PC itself or an XT).

If you've been cramped lately and have already reorganized, thinned and defragmented your disks, look to compression for some elbow room.

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