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Programs Put More Chunks on a Chip

IN ancient Babylon, information overload was measured in pounds. Clay tablets were heavy and bulky.

Humans have since improved on the idea: papyrus-based scrolls, bound books, newspapers, microfilm. The computer age has its own technology for squeezing bigger chunks of information into smaller packages. It's called compression.

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The hottest area of compression research right now is high-definition television. Several companies are competing to have their standard accepted by the federal government. It's really a test of whose math formulas do the best job of squeezing information so that it flows through the broadcast channel and unsqueezing it at the other end. The big gains come from techniques known as lossy compression, which approximates data. Viewers won't see high-definition TV for another few years.

But computer users are already taking advantage of another information-squeezing technology called loss-less compression. Unlike lossy techniques, it stores data intact. Chances are, you've already encountered it.

If you've loaded new software, the installation program probably used some kind of compression. Maybe you've downloaded a file from an electronic bulletin board and "unzipped" it - the popular decompression method from Pkware Inc. Maybe you have a program to back up your data. The two backup programs on my computer use compression technology licensed from Stac Electronics.

From these peripheral areas, compression programs are ready to take center stage and compress your entire hard disk. Microsoft may include the technology on its next version of DOS (although Stac has filed suit for patent infringement).

DR DOS, the DOS alternative, already incorporates a compression program. Other companies are vying to convince PC and Macintosh users to squeeze the information that resides on their hard disks.

I have to admit I've been leery of compression. Sure, it worked to back up files. But my crucial, everyday data? Stored on the electronic cousin of a trash compactor? I gingerly loaded Stac Electronic's Stacker onto my computer.

The installation took a long time. But the results were worth it. As promised, Stacker doubled the size of my disks. My 90-megabyte removable Bernoulli drive grew to 180 megabytes.

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Stacker looks at each group of 2,048 characters and finds the repetitions. In the sentence: "So the thing that counts is theology," the program spots four instances of the three-character string "(space)-t-h." It stores the first instance, then uses pointers to recall the location for the other three. Pointers save space because they can be as small as 11 bits, while a three-character string takes 24 bits.

Save a file and Stacker automatically compresses it. Open it, and Stacker returns it to its original format. On my machine, I found no noticeable delay. I'm a compression convert.

Loss-less compression will become even more powerful as users move to more advanced operating environments, such as OS/2 or the promised Windows NT and machines with more memory, predicts Phil Katz, president of Pkware. The Brown Deer, Wis., company has just come out with a new version (2.04) of PKZip and is working to put its software into a chip that would speed up the process.

Stac, which already has a hardware-software product, is creating new hardware versions. The company is creating a compression chip that would allow two local-area networks to communicate much faster over phone lines. Stac is also working on a version for a VESA local bus. VESA local buses are newly popular gizmos that accelerate a computer's video performance. By hardwiring Stacker into the board, the company is finding that programs stored on the disk speed up too. Bob Monsour, Stac's vice president of product development, says a product would likely appear later this year.

Try compression, if you haven't already. It's one of the few oases in an age when information is as burdensome as ever, clay tablets notwithstanding.

* Send your comments on this column to CompuServe (70541,3654) or Prodigy (BXGN44A).

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