You will awaken some morning five years hence, speak a few simple instructions from your bed to your toaster, coffee pot and frying pan, and walk into the kitchen 15 minutes later to a fully prepared breakfast.

The same small computer that's wired into the walls of your house and built to recognize only your voice will turn on lights when you walk into the kitchen and turn them off when you leave. It also will turn the refrigerator off when you leave for work and turn it back on before anything defrosts. Your furnace and air conditioner will respond to the same computer, driving warm or cool air into only the rooms that are occupied.

Your home computer will pay your bills and balance your checkbook. It will order your groceries, plan your meals and suggest recipes for dinner guests on diets or with fussy appetites. It even will open the front door for you, responding without locks and keys to the sound of your voice. All you'll need to say is Open Sesame.

These are not mere flimsy forecasts. They are the commercial results of products already being tested.

They are at the core of what Sperry Univac's Earl G. Joseph calls the "smart machine revolution," where the people busy building bigger and faster computers finally have figured ways of making them small and cheap enough to move into the home.

"These machines are personalized; they're not Big Brothers," said Joseph, who is Univac's chief scientist in St. Paul, Minn, "They're friendly machines . . . they're your machines."

Now on the market is a $500 computerized wristwatch that reads its wearer's pulse. Next will be a simllar watch that takes temperatures, surface skin conditions and blood sugar levels. Perfect, for diabetics, with a predicted price of $20.

Prisons, factories and even a few homes have door with built - in computers that open on voice command. Airliners now have tiny computers in their wheels that sense any change in tension that suggests a skid and automatically release the wheel Jocks to avoid skidding.

One maker of farm equipment is testing a driverless tractor whose computer senses and follows the turns and furrows of a small test farm.

A Detroit auto maker's test computer goes to work after the car is parked: Another car backing alerts the test car's computer to release the brake, start the engine and back out of the way.

Cars already are using the smart machines. General Motors Corp. this year put tiny computers in the engines of 30,000 Oldsmobile Toronados to sense things such as engine speed, coolant and air temperature and manifold pressure, then advance and retard the spark to extract the most efficiency from the gasoline.

Chrysler tried the same thing last year and found it worked so well that this year it's in 500,000 eight-cylinder Chryslers, adding at least one mile of driving per gallon.

Next year, Ford Motor Co. will make a six-cylinder truck engine whose computer will "tell" it when it can run on three cylinders (downhill) to save gas. About 30,000 Ford cars will get the same kind of spark timer Chrysler and Oldsmobile already have. Another 30,000 Pintos and Bobcats in California will be equipped with a computer to recirculate the exhaust gases that otherwise would be air pollutants.

In a matter-of-fact voice that belies the speed of computer progress, Univac's Joseph says the cars of the future will be equipped with radars the size of headlights to sense oncoming cars. They'll also have computers to sense road conditions, car speeds and driver response, all of which will be calculated quickly to steer the car out of the way of an impending collision.

"We'll make the system redundant so it will be fail-safe," Joseph said. "When that happens, drivers will no longer be sued if they have collisions. Whoever makes and supplies the system gets sued, just like the people who supply pacemakers that fail" to regulate the human heartbeat.

Behind all this change is the fact that computers are shrinking in size and cost at a speed unmatched in their 25-year history.

Magnetic memory devices 20 millionths of an inch across are commonplace. Circuits even smaller are being mass produced. Computer circuitry has become so small that it's installed with the help of eptical and even electron microscopes.

"We believe we can shrink things down to where circuits will be no wider across than half the wavelength of light," said IBM vice president and chief scientist Lewin N. Branscomb. "We'll get to where we have thousands of circuits together on a board the size of your thumb."

Thousands of thumb-sized circuits means computers for just about anybody. In the last year alone, more than 300 shops have sprung up across the country retailing small computers. Macy's of California is getting into the business. So is Radio Shack. Estimated sales of $50 million this year are expected to reach $1 billion by 1985.

Typical of the homegrown craze for computers is the success enjoyed by Microsystems Computing, a Springfield, Va., store owned by Russell and Gloria Banks, who left their jobs less than a year ago. Sales have jumped every month and will reach $60,000 this month.

Who buys their $500 computers? Gourmets who start out storing recipes on the computers and end up keeping all their financial records on them. Hobbyists who play electronic games piped onto their television screens (the most popular is Star Trek, where the computer devises galactic traps for the players to escape from in electronic spaceships).

"The time is not too far off when we'll be getting our mail at home by computer," IBM's Branscomb said. "We're seeing the first beginnings of the utter involvement of the layman in computer technology."