If you're the kind of person -- and there are many of us -- who is inept with mechanical gadgets, unable to master the digital radio-alarm clock or the pocket computer, or even the washingt machine . . . .

Be reminded that faster than you think, the computer, the ultimate gadget, is infiltrating our homes and our lives. True, the computer has been with us for a long time: in airline offices and payroll departments and for monthly bills.

But many of us haven't yet had to meet the computer face-to-face. All that is changing.The computer is rapidly moving frm the business world into out homes. The time is coming, say the harbingers of the computer age, when not knowing how to operate a computer may be a handicap. At least for a while.

"no question about it," says William von Meister, whose McLean-based Digital Broadcasting Corp. this month introduced "Source," a $595 information computer. At a cost of $2.75 an hour, charged to your American Express or Master Charge, "Source" can run a mortgage analysis, or plug into the latest wire-service news reports or pork-belly futures in Bismarck. The devices are being sold at a rate of about 150 a week, he said.

A high-powered group of 28 people planning a White House conference on libraries for mid-November was introduced last week to one aspect of upcoming computer life. They came to Washington from all over the country to pick up portable data terminals -- which look like small typewriters with extra keys -- to take back to their homes in Oklahoma, Montana and California.

Nicholas Johnson, former Federal Communications Commission firebrand, took to his data terminal like a child with an exotic new Christmas toy.

"i'm no gadget man," he said, pulling out an old-fashioned pocket watch, but he added that operating computers "is something we're going to have to learn, like driving a car. You'll be handicapped without computer knowledge now.

"i've been talking about this coming up for the past 10 years. Now it's here, and we've got to learn how to operate them."

On the other hand, publisher Helen H. Meyer of New York City was apprehensive, but determined: I'm not mechanically inclined, but after all, I did run Dell Publishing Co. for over 50 years -- and that didn't bother me."

"sure, there's apprehension," said Margaret S. Warden of Great Falls, Mont., a member of the Montana State Advisory Council for Libraries. "But my mind is wide open and I'm all for it." She acknowledged that learning the special language of a computer "was like learning a foreign language."

After hooking the terminals up to their telephone receivers, the library experts are to punch out a special code that will plug them into a central computer and enable them to send and receive messages to and from Washington and among themselves. Thus, most of the conference planning will be done from their homes, saving them costly trips to Washington and waiting for the mails to circulalte paperwork. The $2,995 "Silent 700" Portable Bubble Memory Data Terminals are on loan from Texas Instruments.

The home computer is, in fact, with us in other ways. In addition to "Source," there is Radio Shack's $499 home computer that can help you handle your accounts or your classwork, as well as provide some video games. Other firms are about to market systems that will utilize your television set to plug into all sorts of information banks, giving immediate access, for example, to airline schedules or stock-market quotations.

Charles P. Lecht, president of Advanced Computer Techniques in New York who is known as something of a futurist in computers, sees the computer -- in addition to its information and entertainment capabilities -- providing such in-home services as a complete security system or energy monitor. It could, for example, close the drapes or turn up the heat as the weather requires.

Eventually, cheap computer communication, says Lecht, might enable many of us to do out office work at home. A small device could keep watch on a baby in a crib, alerting the parents elsewhere in the house if the baby needed help.

Many people, particularly the young, thrive on this new gadgetry. They're growing up with TV, space flight, big-selling electronics games and "Star Wars."

But not everyone is so welcoming.

"some resistance to new technology is natural," said Larry Stockett, whose new firm, Mircronet, created the automated "paperless office" and is designing an "Office of the Future" for the American Productivity Center in Houston.

"people feel threatened that unless they can adapt, somebody's going to take their jobs," he said. But once they learn to use the new equipment, he added, they won't give it up.

That's one positive note to cheer the mechanically inept.

Another is Stockett's prediction that "people are going to find computers as easy to use as TV," Many computers are being designed to utilize the telephone, he said, "and there are few people who can claim they don't know how to use the telephone."

Lecht predicts that by 1982-1985 there will be little for the average person to learn for home computing beyond "quasi-natural language commands" and some typing. Later, he expects, we will use vocal commands to get the computer to do our bidding.

Stockett agrees that for the time being a lack of computer knowledge can be handicap, particularly in the business world, in which a company may be reluctant to hire or promote a vice president who doesn't know computers.

"people who don't reeducate themselves are going to find themselves technologically unemployed," he said.

One aspect of the computer age that the library conference expects to deal with is the possibility of a gap between the knowledge-rich and the knowledge-poor. Governments, business and the wealthy who can afford expensive computer hardware will have access to information in the data banks, but where will the poor get their information.

The suggestion is that libraries, long as responsitory or our collective knowledge, misght provide inexpensive computer acess the way they provide books and magazines.

"Are we creating a gap," asks Johnson, "between the privileged and the information underclass? How is a kid in Southeast going to get this information if he can't go to the library or his school? The White House conference must address this issue." CAPTION: Picture, Nicholas Johnson, left and Helen Meyer watch the print-out from a computer termina attached to a telephone line. By Gerald Martineau -- The Washington Post