We all know Betty White. Whether it’s “Golden Girls,” “Hot in Cleveland,” or “The Mary Tyler Moore Show,” she’s been a mainstay on TV for as long as most of us can remember. Long celebrated for her comic timing, the actress began cultivating the skill at her first TV job. In this exclusive clip from “Betty White: First Lady of Television,” a new PBS doc, White discusses her on-screen debut as Al Jarvis’ Girl Friday on his variety show.

White and her co-stars acted live on “The Al Jarvis Show” Monday through Saturday, for five and a half hours per day. “No script, no anything. It was like going to television college,” White remembers. “It was wonderful.”

It was wonderful for her audiences — and her acolytes — too. “Doing that much live television that long gives you a skill set,” Valerie Bertinelli (the original “One Day at a Time”) observes. “She had to start with that skill set, let’s be real. But she honed it in those four years, really quite well.”

“First Lady of Television” is a celebration of White’s 80 years working in TV, her achievements, and her status as “an industry pioneer.” She’s marked many milestones throughout her career, including being “the first woman to produce a national TV show, the first woman to star in a sitcom, the first producer to hire a female director, and the first woman to receive an Emmy nomination.”

Tina Fey, Valerie Harper, Jennifer Love Hewitt, and many more of White’s friends and co-workers join Bertinelli as interviewees.

“Betty White has created some of the most memorable characters in television history,” said Jerry Liwanag, vp of PBS Fundraising Programming. “This new special reveals that she’s been a groundbreaking pioneer since her earliest days in the fledgling medium — both in front of and behind the camera. Her talent and creativity are timeless, transcending generations and cementing her legacy with each passing decade. She’s truly one of a kind.”

“Betty White: First Lady of Television” airs on PBS tomorrow, August 21. Find out more about White’s time on “The Al Jarvis Show” in the clip below: