Betty Anne Williams was a high school junior in Orangeburg, S.C., when three black students were killed and more than 30 others shot by state troopers on the campus of the state college there. The events, which occurred Feb. 8, 1968, and became known as the Orangeburg massacre, gave Williams, who was sworn in last night as the first black president of the Washington Press Club, a focus for her life.

"It made me pay attention to things," said Williams. "We were going pretty blithely along in our very comfortable, pretty good all-black high school. This brought the rest of the world home to us, made all of us think more about our larger communities, and what we were going to do to fit in. That probably crystallized my decision to go to a white school."

Life had been routine in the segregated Orangeburg of Williams' childhood. The students who were killed, including a close friend of Williams', were trying to integrate a bowling alley. "The whole town was on edge--Orangeburg became an armed camp for a while. I had no preparation for that; nothing like that had ever happened."

Though the Orangeburg incident did not immediately turn Williams into a civil rights activist, she took her own step last night as a black "first."

Williams, 31, a reporter with The Associated Press, became the first black president in the club's 64-year history. The Rev. Jesse Jackson, a fellow South Carolinian and the best-watched noncandidate for president, administered the oath.

"Tonight is a major statement," said Jackson, who opened the ceremony with a somber portrayal of minority progress in some industries and a lack of progress in others. Before administering Williams' oath of office on a stack of AP copy paper and a fiscal year '83 budget book, Jackson noted, "The journalism world has remained closed. This is breakthrough."

For the ceremony at the Botanical Gardens, Williams chose a South Carolina theme--fried chicken, spareribs, biscuits, pecan pie and jazz by the Jeff Anthony Quartet. Among the 200 guests were Health and Human Services Secretary Margaret Heckler; M. Carl Holman, president of the National Urban Coalition; John Jacob, president of the National Urban League; and South Carolina Lt. Gov. Nancy Stevenson.

"It seems to be a time for people named Williams," said Housing and Urban Development Secretary Samuel Pierce as he congratulated Williams. He was not the first nor the last person at her swearing-in to refer to Vanessa Williams, recently crowned as the first black Miss America, or Lt. Col. Guion Bluford, the first black American astronaut.

Jackson walked up to Pierce and said, "I'd like you to meet my homeboy," introducing South Carolina Sen. Ernest Hollings, a declared presidential candidate. Pierce, posing with the two Democrats, said, "We are all coming together for history. No one can quarrel with that."

Betty Anne Williams, when asked about Jackson's bid to be another first, said she thinks he should run: "I don't see how he can avoid it now. It's gone too far and has a life of its own."

Yesterday afternoon, she had stepped to the other side of the reporting ropes for a photo opportunity with President Reagan in his office.

Until now, her advance through the Washington journalistic ranks has been steady and low-key. Chatting over breakfast, Williams recalled one of her few scoops. "Well, I was the first reporter Wayne Hays told that Elizabeth Ray could not type," she said. Williams laughed easily, showing the humor and the modesty her colleagues describe. She is also known as independent, dogged, organized, caring and reliable.

"On her 30th birthday the bureau gave her a rocking chair, but no one expects her to wear it out," said Margaret Scherf, a reporter at the AP. "She knows her mind. When we went to Spain, she stayed in the room to play Scrabble, rather than attend a bullfight. And in Tangiers she would not get on a camel to have her picture taken."

In keeping with her understatedness, she forgets the day she caused a stir at the Department of Health and Human Services. Before James Wyngaarden's first press conference as the director of the National Institutes of Health, the reporters were trying to decide who would ask the obligatory question on abortion. While everyone else was balking, Williams took charge. Wyngaarden's reply that he favored "freedom of choice" made the headlines, prompted a clarification by then-secretary Richard Schweiker and a call for Wyngaarden's resignation by anti-abortion groups.

Williams likes a challenge. She went after the complicated health policy beat at the AP. She bought a three-story house in the Bloomingdale section of Northwest while most of her friends were still in furnished apartments. That kind of pushing was emphasized by her parents; her mother taught high school for almost 30 years and her father drives a taxi. Her younger sister is a social worker. "Hard work, thrift and honesty" were the values in her Baptist home. On her couch yesterday was a book, "Speaking Up," a gift from her mother.

After graduating from the University of South Carolina, she worked for the AP in Columbia, S.C., and Charlotte, N.C., for 20 months before joining the large and competitive Washington bureau in August 1974. First she was a regional correspondent, covering the issues and people of Ohio, Pennsylvania and New Jersey. Besides HHS and related health agencies, she now covers some civil rights organizations. After her election, the AP activated a phone line in the House gallery that it had disconnected after former AP reporter Peggy Simpson's term as club president.

Williams was not a plaintiff in the successful class-action charging the AP with sex and race discrimination, but she will receive monetary settlements from both the women's and the black pots. "It was my personal preference" not to join the suit, she said. "I didn't think it would help my career at AP."

Williams has been a member of the 600-member press club since 1975. "This was a good way to have a political outlet, without taking sides that would affect my work," said Williams. She rose through the leadership by joining the board and cochairing the club's "Salute to Congress" dinner in 1979, a prestigious annual political event.

Her career at the club has had challenges and one minor wrinkle. A project she initiated, a 1983 calendar, didn't make any money. "It was a big disappointment," she says. "I did that to test my organizational skills. There has to be something at intervals, something new." She plans to take that philosophy through the year of her presidency. "It's a good test of my energy and ability."