A computer column in yesterday's Washington Business listed an incorrect telephone number for the Expressware software company. The correct number is (206) 481-3040. (Published 8/18/87)

A recent column dealt with "shareware," the unique marketing concept in which software for the IBM PC and compatibles is distributed "free." But shareware authors request that if you use it, please send the registration fee.

Several programmers are prospering using this concept, especially the authors of PC-File, PC-Write and the modem communication program Procomm. These three companies each have annual revenue of more than $1.5 million. While they are the most successful, their programs are not the only top-notch shareware. Here are others: QMODEM. Now in version 3, this communications program is second only to Procomm in power and popularity. It uses commands familiar to anyone who has used PC-TALK, the classic communications program that began the shareware concept. But it is faster and makes extensive use of on-screen windows.

Its author, John Friel, is moving and currently has no mailing address. But the program is available from computer bulletin boards and user groups nationwide. It is also available from PC-SIG (more about that later). Registration of Qmodem is $20. FILE EXPRESS. This menu-driven data-base program has become a favorite with those who need a filing program that is fast and easy to use. Now that PC-File has grown into a more sophisticated package, File Express seems likely to capture the loyalty of many who want a data base they can start using without plowing through a lot of documentation.

Registration is $40 and includes a nicely bound looseleaf manual, plus telephone technical support. Write Expressware, P.O. Box 230, Redmond, Wash. 98073, or call (216) 481-3040. You will be joining an estimated 5,000 other registered users. PC-DESKTEAM. This is a desk-top utility package similar to the smash hit Sidekick, but it has features Sidekick lacks. Like Sidekick, Deskteam loads into background memory, where it is available anytime at the touch of a key. Also like Sidekick, Deskteam has a calculator, calendar, phone dialer (with directory) and notepad. But unlike Sidekick, it includes an alarm clock and, best of all, a selected set of DOS commands. These allow you to get a directory, check the space on a disk or even copy a file, all without leaving whatever else you are doing.

Deskteam would be preferable to Sidekick except for one thing -- its notepad is a limited text editor, whereas Sidekick's is quite a complete one. Registration is $25. Write Alternative Decision Software, P.O. Box 307, Lancaster, N.Y. 14086. No phone listed. AS-EASY-AS. As its name suggests, this is a spreadsheet that anyone who has used Lotus 1-2-3 (or its clones) will pick up immediately. It can read Lotus files and has much of Lotus' power, except for the limited data-base functions that some Lotus devotees find indispensable. And As-Easy-As cannot handle as large a spreadsheet as Lotus can.

Still, it is all many users will need, and it is also a good way to learn Lotus without having to spend $300 to buy the original. Registration for As-Easy-As is $30. Write Trius Inc., 15 Atkinson St., Lynn, Mass. 01905. No phone listed. QUBECALC. This is another Lotus workalike, with a big difference: It is three-dimensional. It works on more than one spreadsheet at a time, allowing them to be viewed from various perspectives. Thus a table of figures showing monthly expenses from one year can be combined with similar tables going back several years. Then the "cube" can be rotated, permitting the figures to be viewed by category year-by-year, month and so on. Qubecalc will read Lotus files. Registration is $49.95, plus $5 shipping. Write FormalWare Co., P.O. Box 21726, San Jose, Calif. 95151-1726, phone (408) 226-5415. Ask Qubecalc's author, electrical engineer Bruce Busby, about his other shareware product, Instacalc, a RAM-resident spreadsheet.

Other shareware gems include Automenu, an easy-to-use program that creates customized menus to run your computer. It is ideal for helping novices avoid the agony of learning esoteric commands.

There is also Galaxy, a powerful menu-driven word processor, and New York Word, another full-featured word processor. There are disk-management programs, outline processors, drawing programs, games and more.

Fortunately, there is a central location where you can find nearly all of these. It is PC-SIG (Personal Computer Software Interest Group), a national clearinghouse that has compiled more than 700 disks and publishes a paperback directory (the PC-SIG library) and newsletter. You can get disks from PC-SIG for $6 each. The address is 1030D E. Duane Ave., Sunnyvale, Calif. 94086. Phone: (800) 245-6717.

And wherever you live, chances are there's a nearby PC user group with a software library that has a lot of the best shareware. User groups are good places to get not only shareware, but also to obtain help in using it.Brit Hume is a contributor to the Washington Post Writers Group. Hume is an ABC News Capitol Hill correspondent and the founding editor of a computer newsletter