Something new has been added to the game-within-the-game known as covering the point spread. Home computers are being purchased in large number, whether they be for family fun or for the programming of serious mathematical probabilities.

A year or so ago, the Mattel Corp. came out with a system designed to help horse players make money at the races. Mattel's figures were supposed to be better than those of professional handicappers.

It hasn't quite worked that way, to my knowledge. And I don't think your friendly neighborhood computer store is about to base its profit projections for the fiscal year on how many football fanatics are attracted to the computer workshops and education or training centers.

But the software is fun to play with, I'm assured. So, if Mom and Dad and the kids want to believe the Osborne I or Apple II is the key to determining whether the Washington Redskins are ready to embark on a trip to the Super Bowl, why not have a go at it? The computer predictions could hardly be worse than those provided by many private services.

"We have a number of families that already are into using the home computer to help them select the results of golf tournaments," said Jane Mason, who teaches computer technique at a Rockville outlet. "Once we get into football, I'm sure there will be even more interest in trying to do the same thing."

This, then, is an invitation to Mason and other computer experts to get in touch with "Playing Football" this month in time to start comparing notes. What I'd like to do is to keep track of how the machines are faring over the first half of the NFL season. I'll document their won-lost record against the spread, week by week, and report on how successful these ventures have been.

A word of warning: it's not an easy game, no matter how simple or how sophisticated the approach.

I remember, in 1978, a knowledgeable gentleman called from Hyattsville. He worked with computers by day and had obtained permission to stay on at night and develop what, he believed, was a sure-fire approach to making big money betting against the numbers.

Over the first three weeks he was 10-4. The fourth week did not sustain the winning, although the loss was small. Week 5 produced a small profit. Then the trouble started.

"I didn't like some of the picks the computer had made in the early weeks, yet they turned out right," the man said. "But in the sixth week it fed me the Giants getting 13 at Dallas and Atlanta getting 10 1/2 at Pittsburgh and I thought, going in, something must have blown a fuse."

Dallas beat New York, 24-3, and Pittsburgh won, 31-7.

That was the beginning of the end. By the time the conference championships were played, the computer operator was convinced he knew more about football than his machine did. He backed Pittsburgh giving seven points over Houston and Dallas at Los Angeles. The machine's calculations went the other way. The scores were 34-5 and 28-0, favor man over machine.

"What I found," the gentleman said, "was that I had more fun, win or lose, by doing my own picks. I didn't really like it when the computer won in situations where I thought it was stupid."

I couldn't agree more. The enjoyment in attempting to cover the spread is highly personalized. It is a mini ego trip when you are right. If someone else does the work and makes the (mythical) money for you, the kick isn't half as strong.

So here's to the individual, as he prepares to go forth for 20 weeks risking $11 to win $10 against the spread in 1982. Who needs a calculator when, deep in our hearts, the veterans of Playing Football believe that nothing, except maybe a strike, will be able to stop us.