Here are utilities to boost capacity of your hard disk

PERSONAL COMPUTERS

December 28, 1992|By PETER H. LEWIS

Even a couple of years ago, 40 megabytes of storage seemed like Santa's sack: a bottomless repository.

Today, thanks to color graphics, sound and byte-spewing engines like Windows and OS/2, some PC buyers consider 100 megabytes a minimum, and even 200MB does not seem greedy. Hard disks are like attics or garages; regardless of size, they soon become cluttered.

The problem becomes acute with notebook computers, which typically have smaller disk drive capacities than their desktop cousins.

The standard solution is to buy and install a new hard disk. But we all know that some bosses (or spouses) are not amused by these annual requests for more computer equipment. Also, installing a new hard disk can be an ordeal.

The easier and cheaper solution may be a file compression utility. One of the best is Stacker 3.0, the newest version for DOS and Windows computers. Versions of Stacker for Macintosh and OS/2 computers are promised for spring.

File compression software analyzes a file and looks for patterns that can be reduced to a smaller number of bits, or tokens.

Take, for example, the word "the." The sequence is usually space, t, h, e, space -- five characters, or bytes. Because a byte is 8 bits, the sequence takes 40 bits.

Stacker looks for the second occurrence of "the" and replaces it with a shorthand token, plus a pointer back to the first occurrence. Every subsequent "the" takes 11 bits, rather than 40.

The ratio of compression varies, depending on the type of application and file format, but a good compression program will effectively double the capacity of a disk. In other words, a 40-megabyte hard disk that has been filled to the brim will suddenly have about 40 megabytes of extra free space, for a total of 80 megabytes.

The best programs accomplish this compression at such speed that the user never notices the inflations and deflations going on inside the computer. Microsoft Corp. is reportedly planning a compression utility in DOS 6.0, the next release of the operating system used by most personal computers. The rumor mill says Apple Computer Inc. is planning to add compression to a future version of its Macintosh operating system.

Microsoft added file backup functions to earlier DOS versions, yet people still buy backup programs, because they do more than the DOS version does. So, the possibility that Microsoft will add compression to DOS does not necessarily put the squeeze on the many compression utilities on the market today, including Stacker, PK-Zip, XtraDrive, SuperStor, StuffIt and Auto Doubler.

Some compression utilities, like PK-Zip, are typically used to compress a single file, perhaps a graphic to be sent to another computer via modem. I have zipped and unzipped files by typing in strings of odd DOS commands that resemble the Klingon dialogue subtitles from the "Star Trek" movies, and it is a bore. But the compression pays off in shorter long-distance toll charges and in less wasted work time while waiting for the file to be transferred.

Others, like Stacker, compress the whole hard disk and decompress files when they are needed. This is called on-the-fly compression, and the user need do nothing special to take advantage of it.

The new Stacker 3.0 installs easily from either DOS or Windows. Windows users will see a "stackometer," which shows the capacity of the disk and the level of compression. It is a nice touch for people who are not technical. The techies can tweak Stacker to maximum compression, giving up a little speed in return for a few extra megabytes.

Stacker 3.0 has some other slick features, including better password protection to keep snoopers away from files and an "anywhere" feature that allows compressed floppies to be used on computers that do not have Stacker installed.

Stacker works with most disks, from floppies to the latest flopticals. It can double drives up to a total of 2 gigabytes (2,000 megabytes).

Stacker 3.0 for Windows and DOS has a list price of $149. An upgrade from a previous version is $49.95. The program requires 640 kilobytes of memory and 2 megabytes of vacant hard disk space, plus a version of DOS no older than 3.2 For information, contact Stac Electronics, 5993 Avenida Encinas, Carlsbad, Calif. call (619) 431-7474.

(Peter Lewis works out of the New York Times' Austin, Texas bureau: [512] 328-8258.)

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