NEW YORK — During her lengthy career, Carol Burnett has shown she's a fine dramatic actress in films like "The Four Seasons" and "Friendly Fire."

She has the sort of singing voice that can fill a Broadway theater, and did, when she starred in "Once Upon a Mattress."

But more than anything, she is a comedian and a TV institution, demonstrated beyond question on her CBS variety series, "The Carol Burnett Show."

It was there she embodied countless madcap characters, and where, for an 11-season run that began 40 seasons ago, she piled up indelible TV moments: her charwoman, her Tarzan yell, her tug of the earlobe as a signal to her Nanny.

There was also the ritual with which she opened each show: taking questions from the audience. Weekly, she stepped from behind a character or song to reveal herself, with cleverness and charm, to her fans. They loved it.

We still do. So a scattering of Q-and-A excerpts serves as an apt structural device for her "American Masters" portrait.

Premiering at 9 tonight on PBS, "Carol Burnett: A Woman of Character" starts with an audience member from a distant broadcast asking Carol to recall her most embarrassing question.

"It was whether I had ever had a sex change," she replied. "I think that takes the cake."

The next person's question — "Did you?" — set off a second explosion of laughter.

With Burnett's full participation "A Woman of Character" tells her story.

She was a child of alcoholics who grew up poor a few blocks (but a world away) from the glamour of Hollywood. Still, she immersed herself in Hollywood. With Nanny, the grandmother who raised her, she took refuge at the movies, as many as eight of them a week. Then, with her friends, she acted out the characters she met on the screen.

At the University of California, Los Angeles, she discovered student theater and realized she was funny. She moved to New York. She proved herself on the stage and, more important, on live TV. By her mid-20s she was a star.

"A Woman of Character" charts these steps, and reminds us how special she is: a comic performer combined with a clown; an actress full of zany identities but also a woman her audience identifies with.

"I don't think you can get more American than Carol Burnett," says Kenny Solms, who was one of her writers, in the film. "She really is apple pie."

In September 1967, she got a show of her own, with a dream team that eventually included Harvey Korman, Tim Conway, Vicki Lawrence and Lyle Waggoner (all heard from in the film).

"God, we laughed for 11 years," Burnett, 74, marveled recently.

How does she channel all those characters so convincingly?

"What helped me a lot was deciding how I was going to look," she explained. "I work from the outside in."

As she did with the airhead secretary Mrs. Wiggins, who was forever exasperating her dweebish boss (played by Conway, who conceived the skits). "Tim had written her as an elderly lady," Burnett said. But the show's costume designer, Bob Mackie, had a different take.

"He said to me, 'I think she should be this vapid thing, always putting on lipstick and checking her nails.' So he puts me in the blond wig and the blouse with the push-up bra. And he found this old skirt on a rack somewhere." A very short skirt. "But it was baggy in the behind." Burnett laughed at the memory.

"I said, 'You're gonna have to take this skirt in, 'cause I'm flat back there.'

"But he said, 'No, just stick out your behind. Put your behind INTO it.' That baggy skirt and the high heels gave me the walk," she summed up, making it seem so easy. But that's part of Burnett's character, too.