What was going on when I was born?

A videotape played yesterday at the bribery trial of Senator Harrison A. Williams Jr. of New Jersey shows him discussing a mining venture with Abscam undercover agents and agreeing to have a concealed interest in it. The Senator also says that he could ''with great pleasure talk to the President of the United States about it.'' The tape was made surreptitiously by the Federal Bureau of Investigation in a motel in Arlington, Va., in June 1979, when Jimmy Carter was President. Prosecutors at the trial in Federal District Court in Brooklyn say that the videotape is a key piece of evidence showing that the 61-year-old Democratic Senator agreed to use his position to obtain Government contracts to buy the output of the mine.

The actress Jodie Foster said today that she received ''several pieces of unsolicited correspondence'' last fall from the suspect in the shooting of President Reagan and that she had thrown them away. But when she received ''three or four more notes'' at the beginning of March, the 18-year-old Yale freshman said, she gave them to her dean. ''In none of these letters and notes I received was any mention, reference or implication ever made as to violent acts against anyone, nor was the President ever mentioned,'' she said this afternoon, reading a statement to six reporters invited to meet with her. ''Because they came in more frequently,'' she added in response to a question about the letters, ''I automatically didn't want to assume anything, and I gave them to the dean in order to be safe.''

Ending weeks of speculation, Governor Carey and Evangeline Gouletas, the Chicago real-estate developer, announced tonight that they planned to be married April 11, the Governor's birthday. The Governor's office confirmed the plans after Miss Gouletas informed Mayor Jane M. Byrne of Chicago by telephone while the Mayor was being interviewed by a newspaper reporter. In a brief statement, Mr. Carey's press office said the wedding would take place in New York City. The statement said arrangements were being handled by Letitia K. Baldrige, the White House social secretary during the Kennedy Administration.

Secretary of Defense Caspar W. Weinberger has ordered his first extensive reorganization in the Pentagon. He is delegating greater planning authority to the service secretaries and to the Joint Chiefs of Staff in an effort to free himself to focus on policy. The Secretary, in an order that revises the way that annual and long-range military budgets are prepared, appeared to be seeking to reverse the centralized procedures established by Secretary of Defense Robert S. McNamara 20 years ago. Memo Signed by Carlucci A memorandum to senior Pentagon officials setting forth the new process was signed by Deputy Secretary of Defense Frank C. Carlucci, reflecting his considerable role in the Pentagon in making policy and seeing that it is carried out. Mr. Carlucci also was Mr. Weinberger's deputy at the Office of Management and Budget and in the Department of Health, Education and Welfare.

International Egyptians say they oppose U.S. role in Sinai force A2 U.S. terminates economic aid to Nicaragua A3 Around the World A6 For Istanbul youth, return to farm is not a way out A7 In Shanghai, mute reminders of China's break with the past A8 Khomeini seeks purges of judiciary and revolutionary guards A9 Polish union ousts official A10 West German Foreign Minister due in Moscow today A11 Second Islamic peace effort in Gulf seems to end in failure A11 Yuri Trifonov, writer, given official funeral in Moscow A12 Quebec nationalists take unexpected lead in poll A16 Reagan Shooting President is moved to private hospital room A22 Sen. Kennedy ready to compromise to pass gun control bill A22 Government/Politics Chicago Mayor's first night in ghetto housing is 'very quiet' A18 Koch reported about to replace Board of Standards head B3 Representative Rosenthal questions advertising by Invsco B5 Navy drops contract for 9th Trident submarine at Groton B10 General Around the Nation A18 Former People's Temple aide confessed to 5 killings A20 Judge refuses to delay trial in slaying of Dr. Halberstam A21 Nursing home strike is postponed after progress in talks B2 Education/Welfare Boston postpones shutdown of public school system A18 Brzezinski returns to Columbia B3 The Home Section Home Making a studio fell spacious C1 What to do in city and suburban gardens this month C12 Children and public violence C1 Improvising a serene rural life C1 Hers C2 Hardware C2 Ban on city water for outdoor pools C3 Home Beat C3 Home Improvement C4 Athena and Hexter awards for design C5 Passover decoration in floral workshop C7 Chihuly glass show features sea forms C8 Where to garage and park your car C8 Design Notebook C10 Arts/Entertainment Catalogues of art exhibits proliferating C14 Film sellers vacate ballroom for academy's banquet C15 Oscar TV show regained some luster this year C15 Workshops for music conductors at West Virginia U. C16 Peter Brook's "Cherry Orchard" captivates Paris C16 "Memorandum for the President" by Carter aides is reviewed C19 Sports Dave Anderson on the plight of the Knicks in the playoffs B12 Trout season has ritual opening B12 Yankees acquire Jason Thompson in 3-team deal B13 Rangers to start a rookie goalie B13 Rams say they have lost Ferragamo to Montreal of C.F.L. B13 Rosie Ruiz still insists she won B13 Gilmore is blocking Knicks' path in playoffs B14 Jones disappointed, Mumphrey elated over Yankee-Padre deal B15 Features/Notes Notes on People B9 Going Out Guide C27 Obituaries Earle Thompson, utility president B17 News Analysis Richard Eder on foreign reaction to Reagan shooting A25 Editorials/Letters/Op-Ed Editorials A26 Swords into sausage for Poland Whom the coal strike will hurt Love for sale Topics: cold/dry Letters A26 William Safire: only one, Secretary Haig, fell short A27 Anthony Lewis: out of a lonely crowd, an assassin A27 Stanley O. Day: the Liberian coup through 'bifocals' A27 Michael R. Gordon: arms and inflation A27

A dispatch from London yesterday about a libel suit involving the Unification Church incorrectly identified a man who had written an article about his son's joining and leaving the church.

"A writer's real material comes from his sufferings. The truest memory is the kind that leaves scars on the heart.

J Robert Fluor's bow tie and folksy manner disguise his flair for the dramatic gesture. When his fast-growing Fluor Corporation arranged last November to invest $12 million in Genentech Inc., he explained the genetic engineering company's relationship to what Fluor does in energy: ''The idea is, we turn some bugs loose in coal and then they chew like hell and turn out oil.'' Mr. Fluor, the 59-year-old president, chairman and chief executive officer of the nation's second-largest industrial construction company, was after diversification - the kind that can keep Fluor growing in the 1980's despite setbacks such as the revolution in Iran, which cost Fluor millions of dollars, or the Reagan Administration's decision not to pursue the Carter Administration's $88 billion synthetic fuels program, an area in which Fluor has a major stake. Big Diversification Move Fluor's proposed acquisition of the St. Joe Minerals Corporation fits into this strategy of diversification. With this deal - in what Mr. Fluor calls ''one big jump'' - Fluor intends to plunge into mining and metals.

The United States Steel Corporation announced today that it would spend ''several hundred million dollars'' to rehabilitate its 100-year-old plant on the city's industrial South Side. Some steel experts said that the announcement signaled a change in strategy at Big Steel, which has been trading some of its natural-resource properties for cash lately. Local officials and steel experts said the program would help to rejuvenate the high-cost complex, which had been put on the company's list as a plant that could be shut down in the industry's current retrenchment phase.

Heavy institutional buying pushed the Dow Jones industrial average up 10.27 points yesterday, to 1,014.14, close to the eight-year high of 1,015.22 that was reached last Wednesday. Lower interest rates and reports of continued improvement in President Reagan's condition following the assassination attempt on Monday aided the New York Stock Exchange rally, market participants said. Big Board volume reached 54.9 million shares, up from 51 million the previous day. There were 932 advancing issues and 614 declining ones.

Fox said it had accepted in principle a reinstated takeover bid by Marvin Davis, days after the Denver oilman withdrew his $700 million offer for the entertainment company. The terms of the deal, to be presented to Fox shareholders by June 25, are nearly the same as those proposed by Mr. Davis in February. (Page D1.) U.S. Steel plans to spend ''several hundred million dollars'' to rehabilitate its 100-year-old plant on Chicago's South Side. The company, which recently has been trading natural resource properties for cash, may be changing its strategy, analysts said. (D1.)

-An insurance broker testified today that he had split a $10,000 insurance commission with Joseph M. Margiotta, the Nassau county Republican chairman, after being informed by Mr. Margiotta that he would receive the check. It was the first time in three days of testimony at Mr. Margiotta's trial, in Federal District Court here on mail fraud and extortion charges, that the Republican leader had been described as receiving some of the $500,000 in split commissions dispensed by the Richard B. Williams and Son insurance agency of Hickville. Both the prosecution and defense agree that the payments went to politicians who were designated by Mr. Margiotta even though they did little or no work for the money. The Williams agency received about $1.5 million in commissions for handling the insurance of Nassau County and Hempstead Township from 1969 to 1979. Mr. Margiotta is also the Republican leader of Hempstead.