WORD processing, which used to be called writing, is what most of us think of first when we are adding a personal computer to our lives. Selecting the right program can be a puzzle, though.

The popular, brand-name programs are expensive, and aren't they difficult to learn? But can the cheaper, easier-to-learn packages do enough? And what about this new thing: desktop publishing?

The top-of-the-line word-processing programs do carry hefty list prices, although substantial discounts are available. Their popularity and their reputations for difficulty are both deserved; they are popular, and tough, because they can do so much.

But there is a secret known to the experienced: You do not have to learn all of a program before starting to use it, and you will probably never have to learn the whole thing. To use a word processor you have to know how to get it going, how to move around within whatever it is you are writing, how to correct mistakes, how to save a document on or fetch it from a disk and how to print it out.

Later, you can learn about conveniences and shortcuts: how to move around paragraphs, change the margin settings and spacing, or dress up the printing. Your new toy probably does mailing labels, but you may never need to learn that.

Ray Mussato, a senior vice president of MicroPro International, publisher of WordStar, divides the world of computerized words into three categories. First comes word processing, the production of memorandums, letters and other documents. Second is word publishing, which marries word processing to the ability to mix type styles and graphics. (An example would be a memorandum with a heading in a type face different from the body of the document, and incorporating a bar chart.) ''Word publishing is the most rapidly growing market segment,'' Mr. Mussato writes, ''and will eventually replace traditional word processing as the product of choice for most home and office use.''

Third is desktop publishing proper. Here the focus is not on what is written, but on how it is presented, the actual appearance of the printed page. This category is fairly difficult to use. You will not want to be stuck with a desktop publishing program when you need a vital report in an hour.

Better Working Word Publisher is a hybrid that fits into the second niche, word publishing. Judged simply as a word processor, it offers an enormous value at $59.95, with features that would have been hard to match for hundreds of dollars just a few years ago.

It has all the capabilities that make writing on a computer, as opposed to a typewriter, such a pleasure. You can write, correct and rearrange words with great alacrity, selecting from a series of menus with either the arrow keys or a mouse. This is one program you can go back to after a month away from it and get back up to speed almost immediately.

The program comes with other conveniences that used to mean high prices or require add-on programs, including a spelling checker with an expandable dictionary of more than 100,000 words, a thesaurus and an outliner.

All this would be more than most of us require. But Word Publisher has still other features to justify its name. With a little more fuss, and a lot more time waiting for the printout, you can choose from up to nine different typefaces in a variety of styles and sizes (but if you want some good advice, please only one or two per document), put graphic images into your documents, set up not just one, but two, three or four columns, and draw lines and boxes for emphasis.

On top of all that, the manual is a model, serving not only as a guide to Better Working Word Publisher, but as a kind of short course in computers. It includes enough information on MS-DOS, the operating system of I.B.M.-compatible computers, to get a novice up and running. I ran the program on a Leading Edge D2, a machine with an 80286 central processing unit and a fast hard disk, and everything worked with commendable swiftness.

I noticed one problem in the manual. It instructs owners of hard disks to create a separate subdirectory, rather like a separate file folder, to store the data created by the program. But the sample documents suggested as trial for the program are not in that subdirectory, and the result is a series of confusing error messages and irritating beeps that could frighten beginners. Don't set up the subdirectory until you are ready to use the program for real.

Better Working Word Publisher is published by Spinnaker Software, 1 Kendall Square, Cambridge, Mass. 02139; telephone (617) 494-1200.