Laptop-friendly software.

LAPTOP-FRIENDLY SOFTWARE This year, according to Dataquest, sales of laptops and other small-scale machines will probably top two million units; by 1993, that number could reach 3.5 million. Clearly, laptops represent a high-growth market--but what does a good laptop application actually look like?

Browsing through "The Complete Laptop Computer Guide," we discovered some useful answers to this question. In an interview with the Guide's author, David Rothman, Ken Skier (developer of the No-Squint Cursor utility and the Eye Relief for Laptops word processor) offers several guidelines for designing laptop-friendly products:

* Deliver good performance on low-end hardware: "That's quite a demanding requirement," says Skier, "because you can buy a laptop with one drive, no hard disk, a speed of 4.77 megahertz, and only 512K of RAM. We haven't seen this class of machine on a desktop for at least five years. But this is exactly the type of machine that's continuing to emerge as lightweight, notebook, and personal computers."

* Minimize disk I/O: Spinning a disk drive to load data or program files is a big drain on battery power, Skier points out. Ideally, he says, laptop software should only require disk access when the program loads or when the user saves data.

* Test color displays carefully: "Often, a program will use screen colors that are absolutely unreadable on an LCD display. If you can't change the colors that such a program uses, then you can't run that program on your laptop. That's bad design."

* Avoid missing keys: Rather than provide a full set of standard keyboard keys, laptops occasionally rely on awkward substitute keystroke combinations. Applications that rely heavily on these "missing keys"--such as outliners, which use the plus-key from the numeric keypad--will be especially difficult to use in a laptop environment, Skier points out.

* Make the text readable: Ideally, laptop software should compensate for poor screen resolution by offering some control over text size and spacing. Skier admits this rule is almost impossible to implement in a standard character-based environment (his own Eye Relief word processor is one of the few exceptions), but he still argues that better readability is still an important design goal.

"Complete Laptop" author David Rothman suggests two other good laptop rules: The software should read and write many different text file formats, not just ASCII; and the help system should be especially good, because users often work on the road, away from easy access to support.

Ken Skier, president, SkiSoft Publishing, 1644 Mass. Ave., Lexington, Mass. 02173; 617/863-1876. "The Complete Laptop Computer Guide," by David Rothman, $18.95; copyright 1990. (To order, contact Sara Gordonson, special sales manager, St. Martin's Press, 175 Fifth Ave., New York, N.Y. 10010; 212/221-7945.)