DECIDING WHICH computer to buy is a bit easier than several years ago when new brands seemed to appear and vanish every week, but the digital market is still a confusing and expensive place -- especially for beginners. Approach buying a computer as you would purchasing a car: Ask questions, read consumer guides and do lots of test driving. The first question, of course, is what do you want a home computer to do? The answer: Everything. You'll want a system the family can use for word processing and running a variety of educational software and games.

IBM, its clones and the Apple II series support the most software but they're expensive systems. Atari and Commodore make reliable, less costly machines but they're also less versatile unless you start adding on -- which boosts the price. I'm biased, because I own one, but I think Apple's Macintosh is far and away the best machine for the (not inconsiderable) money. It's certainly the easiest to use, something that still outrages some hard-core computerists. Even technophobes can make the Mac do their bidding within an hour; children in half the time. Though the standard Mac lacks a color screen, it can accomplish almost everything the average family might ask and it does it without demanding you learn arcane commands and keystrokes.

For more information on hardware you'll want to talk to people in various computer user groups (you can get their phone numbers from computer stores), your best source of biased but free, detailed advice. You should also be reading computer magazines (try Computer Shopper, with articles on all machines and loads of advertising) and trying various machines out in stores, at friend's homes and at your child's school. After completing your research, I suggest a series of long, meditative walks along the river before consulting your checkbook and making a decision.

Buying educational software is easier and less costly. Ask lots of questions and, if possible, try the programs out before purchasing. A few mail order dealers give a 30-day trial on software, but in most cases it's non-returnable unless it's defective. Here's a small sampling of some educational software many educators and computerists think is worth the investment. After each listing is a series of numbers indicating the computers for which the software is available. BRODERBUND Print Shop (6th grade and up: Easy and fun to make banners, cards, signs and stationery) 1, 3, 4, 5* (Key to computers at end) Toy Shop (7th and up: Prints out 20 paper mechanical toys -- all three-dimensional) 1, 3, 4, 5 Where in the World is Carmen Sandiego? (5th and up: Tracking Carmen through 30 cities with 1000 clues teaches geography and problem solving) 1, 4, 5 Where in the United States is Carmen Sandiego? (similar but with 1500 clues spread over 50 states and DC) 1, 4, 5 DAVIDSON ASSOCIATES Math Blaster (1 through 6: Basic math facts taught via tutorial and game format) 1, 2, 3, 4, 5, 6 Math Blaster Plus (Updated with different theme and arcade game style) 1, 2, 4 LEARNING CO. Rocky's Boots (4th and up: Rocky Raccoon's 40 electronic machines teach logic concepts) 1, 2, 4, 5, 7 Reader Rabbit (K through 3: Builds basic skills with games of increasing difficulty; uses digitized speech on the Apple IIGS and Tandy 1000) 1, 2, 4, 5, 7 Math Rabbit (K through 2: Uses entertaining game format to teach number patterns) 1, 2, 4, 5, 7 Writer Rabbit (2nd through 5: Sentence parts are taught with fill-in-the blank questions) 1, 2, 4, 5, 7 MINDSCAPE Success with Math (1 to 8: stimulating tutorial designed by math teachers) 1, 4, 5 Success with Algebra I and II (Covers basics to graphing linear functions) 1, 4, 5 Color Me (K to 5: On-screen coloring kit uses predrawn or original pictures to create cards, coloring books and stickers) 1, 5 Riddle Magic (2 through 12: An 1800 word thesaurus helps kids create riddles and jokes) 1 SIMON AND SCHUSTER Typing Tutor IV (6th and up: One of the best learn-to-type programs -- with entertaining Letter Invaders game) 1, 2, 3, 4, 5 SPECTRUM HOLOBYTE TellStar (2nd and up: An introduction to astronomy with an on-screen planetarium) 1, 2, 3, 4 SPINNAKER SOFTWARE Homework Helper Series (7 through 12: Step-by-step approach to writing papers and solving math word problems) 1, 2, 4, 5 KEY TO COMPUTERS 1. Apple II family 2. Apple IIGS 3. Macintosh 4. IBM and compatibles 5. Commodore 64 6. Atari 7. Radio Shack Color Computer 8. Tandy 1000