Federal buildings all across the country are coming to life. They are becoming in fact what they always have been in name - "public buildings."

In Tulsa, Okla., for instance, the Broken Arrow Superstars were allowed to perform in the inner sanctum of the federal buraucracy. In the Dallas, Tex., federal building, a senior citizens band entertained enthusiastic junior citizens.

In Denver, the Council on Alcoholism uses the federal office buildings conference rooms after hours for its business meetings. In Albuquerque, N.M., the Indian Arts and Crafts Center uses the halls and lobbies of the federal building for its displays and lectures. It also is the place to go in the evening for free mathematics lessons.

New York City's Yugoslavian Council recently held a dinner dance in the historic Old Customs House and a high school held its prom there. The wood carvers club of Central Iowa finally found a meeting place in Des Moines' federal building.

There are about 400,000 federal government-owned buildings in this country. A great many of them are located in the heart of the communities they serve. Until last Thanksgiving all of them were locked up tight after working hours when the federal judges and office workers went home. The result, more often than not, was that the entire area around the building went dark, as actors say about a close theater.

Things began to change when Nancy Hanks, then chairman of the National Endowment for the Arts, decided that artistic awareness, like charity, begins at home. If the federal government was going to help improve the quality of culture in this country, she reasoned, the federal government better try to set an example.

At Hanks' urging, President Nixon, in 1971, authorized the National Endowment for the Arts to set up a federal design program. Under the immediate direction of architect Bill Lacy, this program set out to devise ways by which the federal government might improve the design and livability of its buildings, benefit from the country's artistic creativity and make its signs, posters and voluminous printed matter more attractive. Of all the important contributions the Arts Endowment has made to our culture, the federal design program may yet turn out to be one of the most catalytic.

Efforts by the Endowment's Federal Architecture Program, headed by architecture historian Lois Craig, to find out how federal office buildings can be made more lovable, soon led to an important discovery. It is hard to love than judges and bureaucrats. This let to the Public Buildings Cooperative Use Act of 1976.

The Act permits private cultural and commercial activities to mix with government business in the same building. In keeping with the whole disastrous tendency in the past half century to zone, compartmentalize and segregate everything in this country, this had hitherto been prohibited. Now we can have a newsstand, a cafe or perhaps even a little shopping center on the ground floor of a federal courthouse and office building.

We can build shops into the forbidding wall of the FBI Building along Pennsylvania Avenue and thus make it less intimidating.

And we can help public buildings attract people by using them for exhibitions of all kinds and community events.

There have been efforts before to make public buildings a community asset. The most eloquent of these, no doubt, was a directive issued in 1962 by President Kennedy and drafted by new Sen. Daniel Patrick Moynihan (D-N.Y.) calling for design excellence. The bureaucrats in the General Services Administration, which is in charge of most federal building construction, soundly ignored it.

But this time the nation was lucky. President Carter's GSA administrator, Jay Solomon, a developer from Tennessee, takes a passionate interest in art, good design and the quality of life.

Solomon immediately translated the opportunities provided by the Public Building Cooperative Use Act into action. With a dramatic kick-off last Thanksgiving, he inaugurated a "Living Buildings" program and prodded often-reluctant regional directors and building managers to open public buildings to the public.

It goes without saying that community use of public buildings cannot be allowed to interfere with public business and security or cost the taxpayer money for after-hour guards, heating and cooling, or other special expenses. When such expenses are necessary, the users of the building have to foot the bill.

But opening the doors of entrance halls, corridors, conference rooms and auditoriums for special events is only a smal part of what is needed.

What is needed is public building design and remodeling that builds public use and design into the structure, new or remodeled. Public courts, ground-floor shops, rooftop restaurants, permanent stores, exhibitions, meeting places and all the rest should be an integral part of the architecture.

A public building could be an agora, the market place of ancient Greece, that also was the place of assembly and the heart of the democratic "polis," or city.

Washington's Old Post Office, which a few years ago was to be torn down and is now being remodeled under the auspices of Jay Solomon's GSA, will be a good example. In addittion to federal government offices, this marvelous old building will include attractions that serve what August Heckscher called "the public happiness."