When Juanita Vanderpool of Manassas wants to go out to dinner at an Italian restaurant, she doesn't flip through a newspaper or the yellow pages to find one.

Instead, she hooks her telephone to a television screen and, via a control panel shaped like a flat typewriter, tells it what kind of food she wants, how far she will drive and her price range. In seconds she has a listing of all moderately priced Italian restaurants in Northern Virginia--along with food reviews, specials of the day, maps, parking information and telephone numbers to call for a reservation.

"It's like future shock coming right into your own home," says Vanderpool, 52, of the new system called videotex. "When I was a girl we didn't even have TV and I never dreamed I could have something like videotex. It's the wonder of technology in my lifetime."

Vanderpool's household is one of more than 100 in Manassas that now have a videotex system in their home as part of a market test by ConTelVision Inc. of Atlanta. Manassas was chosen as the company's only test market because it is a community of middle-income families near a major metropolitan center, said project manager John McQueen.

Vanderpool and the others were selected after researchers telephoned 1,000 residents at random. Only those households in which the head of the family was between 18 and 44 years old, college-educated and making more than $25,000 a year were considered, McQueen said. Videotex units that connect the telephone to the TV were placed in the test households last October.

"It is not a home computer," McQueen said videotex. "It is an information bank that hooks up to a regular television set."

Residents testing the system have access to up-to-the-minute weather forecasts, local and national news briefs and a calendar of events for the Washington metropolitan area. They can request such things as recipes or tips on filling out their income tax forms.

There is even a classified advertising section that allows users to pinpoint exactly what they want to buy so that videotex will present only items of interest. And parents can also find out what the Manassas schools are serving for lunch any day, when school activities are scheduled and where the local PTA meeting will be held.

"Videotex is definitely a technology with a range of uses," Edward W. Dooley, spokesman for the National Cable Television Association, said last week. "But right now it is a technology looking for a market. The question is, will people spend money to pull up data on their TV sets that they can look up in a newspaper or phone book?"

An estimated 500 technology firms are banking on the assumption that people are indeed willing. Right now, the race is on to provide the best videotex fastest, Dooley said.

Videotex has become the generic name for a variety of services like that being tested by the Atlanta firm, said Dooley. The concept is that users should be able to request specific information for display on their television screens. But in the race to bring videotex into the American home, technology companies are using telephone lines, cable and airwaves.

"We chose telephone lines because over 95 percent of the people have telephones in their home, whereas 30 percent is considered a good cable saturation market," said McQueen of ConTelVision's strategy.

Currently, the Manassas test market system is the only videotex service available in the District and Northern Virginia.

But Media General Cable of Fairfax, which just last week began installing cable in that county for its cable television service, expects to offer a national service to its home subscribers in September, said company spokeswoman Lorraine Foulds.

The Fairfax cable system will eventually include local classified ads, news, reviews and schedules for its users, said Foulds, although initially the service will provide information compiled by Media General Inc. for users across the nation.

"Videotex is expensive when you have to localize it," said Dooley. Companies must hire people to list such things as local classifieds and last minute specials offered by travel agencies, he said. It can be an expensive operation if only a few hundred people use the service.

McQueen said ConTelVision has spent "several million dollars" on the Manassas test, which includes a central information data bank in Manassas where workers compile and edit information and create graphics for the 100 test market users.

"There is concern that videotex will be a little-used novelty, that people won't think it's worth the cost," said Dooley.

ConTelVision does not charge the people testing their system, said McQueen. He would not estimate how much the system will cost when it is scheduled to be marketed in 1985.

"Our hope is that eventually advertisers will pay the bulk, if the advertising is done tastefully," he said.

Eventually, ConTelVision and other videotex suppliers hope to create a wide-ranging system on which users can do their banking and send messages to friends and neighbors.

"Can't you see that person looking for the restaurant being able to make a reservation on videotex and the maitre d' on the other end confirming it on his videotex?" asked McQueen.

Back in Manassas, Vanderpool and her 18-year-old daughter, Donna, use the system almost every day; that's more than they thought they would when it was first installed last October.

"I would not say it is a novelty: I would say it will eventually be a great source of finding baby sitters, writing checks, doing all your shopping right at home, maybe even getting a date," Vanderpool said. "They said TV was a novelty and too expensive when I was young, and look what happened."