Owning a personal computer can seem like an expensive proposition, especially when you begin adding up the dollars spent on software. But that doesn't have to be the case as is shown through two new books out on public domain software and share-ware.

This software can be obtained on a try-before-buy basis as shareware. I have mentioned shareware before and will continue to do so as it still provides a steady high-quality source of programs for every imaginable purpose.This column discusses two new books that will provide you with reviews and sources of shareware and public domain software.

Public domain software, as opposed to shareware, are programs and utilities written and put into public domain for free by their authors, many of whom are close to being living legends.

Shareware is written for a profit but can be copied and shared by anyone.

The authors expect that after using and evaluating the product, you will send the requested registration fee if you continue to use it.

This system allows authors to write excellent programs, which compete very well with the commercially available software. By eliminating the distribution and advertising costs they hope to make a profit.

Now to the books.

The first is "Alfred Glossbrenner's Master Guide to Free Software for IBMs and Compatible Computers" (St. Martin's, 516 pp., $18.95).

This is 500 pages of lessons, hints, reviews, sources, and even discount coupons for software and access time to bulletin boards and on-line services.

Glossbrenner starts slowly enough so that the novice is led by hand into the world of shareware, mail order, on-line services and bulletin boards.

He gives a very good description of the commercial on-line services such as Compuserve, the Source, GEnie, BIX and several others.

Glossbrenner explains just how to get on-line with each of them and how to search for software in their respective databases.

The book is almost a primer on how to use your computer and modem to obtain software electronically.

He lists and reviews his favorite programs in accounting, word processing, database, utilities, games and even learning programs for children.

His reviews are short but excellent. He gives mini-instruction courses for many of them.

Perhaps his best, and my personal favorite, section of the book is the utilities chapter. Here he lists and reviews some of the best utilities around. These are mostly small programs used to control your computer, such as the way your screen looks.

He has compiled some of his favorite utilities into sets of programs on individual disks, which can be ordered from him at $5 per disk for 5.25-inch disks or $6 for 3.5-inch disks. These collections include many of the programs he writes about in the book.

They include such well-known programs as Procomm, the communications program; PC Write, the famous shareware word processing program; FANSI, the classy screen control utility; and PC-DeskTeam, the Sidekick clone.

The second book is similar in its purpose but a bit different in its approach.

"Public-Domain Software & Shareware, 2nd edition," (M&T Books, 489 pp., $19.95) by Rusel DeMaria and George R. Fontaine, contains basics on telecommunications and how to avoid viruses. There are also chapters on the commercial and private bulletin boards.

Where "Public-Domain" differs from Glossbrenner's work is in its program reviews - and there are almost 300 - which do not explain how to use the software.

The lists are well organized into sections on word processing, accounting, databases, utilities, telecommunications, games, DOS shells and menu programs. They also list learning programs for children.

The two books obviously discuss some of the same programs, but there are enough different ones in each to make them both worthwhile. Both also tell readers where to obtain the programs or utilities.