What was going on when I was born?

Charts and thumbnail outlines of the issues, the background, the key figures: a primer on the gathering at Geneva. Pages A6 and A7.

International Caspar W. Weinberger's letter to President Reagan last week urging him not make any commitments on two key arms issues in Geneva was defended by senior Reagan Administration officials. The officials said the Defense Secretary sent the letter not because he disagreed with present White House positions on those issues, but out of concern that they might not be maintained with sufficient firmness. Asked if Mr. Weinberger was going to be dismissed because of embarrassment over the letter, Mr. Reagan said, ''Hell, no!'' [Page A1, Column 6.] No extension of the 1979 arms pact with the Soviet Union is expected in Geneva. The White House national security adviser, Robert C. McFarlane, said it was unlikely that President Reagan would agree to a joint affirmation with Mikhail S. Gorbachev to extend the 1979 treaty. [A8:3.]

''We get bogged down in technicalities. The big decisions we can make rather quickly.''

The Koch administration has decided to breach its own hiring policy and fill all immediate vacancies for police sergeant on the basis of a racial quota, First Deputy Mayor Stanley Brezenoff said yesterday. The quota system - which will remain in effect until the results of the next sergeant examination, expected in March, are known - will involve at least 1,000 promotions. The next test, an open-book examination designed to meet objections to its predecessor, is scheduled for January. The decision to impose a quota, agreed to by Mayor Koch and Police Commissioner Benjamin Ward at a meeting 10 days ago, was reached after city lawyers concluded that the city could not win pending lawsuits against the results of the last sergeant examination. Court Approval Needed The quota system is subject to the approval of a Federal court and the plaintiffs, who said yesterday that they favored a court settlement based on a quota.

Charles Shultz, creator of the comic strip ''Peanuts,'' closed a public ice-skating rink he owns in nearby Santa Rosa recently, saying he could no longer obtain liability insurance to protect himself against possible lawsuits in case of accidents. Don Oliver, a New Orleans architect, says he and many other members of his profession now practice what he calls ''defensive architecture,'' overdesigning buildings at extra expense in an attempt to pre-empt possible lawsuits. Vincent Catania, who owns five restaurants on Cape Cod, has begun giving classes to employees to help them recognize intoxicated customers who might later decide to sue him if their intoxication should lead to an automobile wreck. ''We've become our brother's keeper,'' he says. They were among many Americans, interviewed last week in cities around the nation, who have begun to change the way they live and do business because they fear being caught up in a rising tide of litigation that is swamping the nation's courts.

The chairman of the House Ways and Means Committee acknowledged today that his committee would fall short of President Reagan's goal of lowering the top tax rate for individuals to 35 percent. Nonetheless, the chairman, Representative Dan Rostenkowski, said that the bill the panel produces would amount to ''the biggest tax reform bill in American history'' and ''a significant improvement over today's tax law.'' The Illinois Democrat spoke at a news conference as his committee began what he said would be the last week of drafting the legislation. The top tax rate now paid by individuals is 50 percent. One of President Reagan's main objectives in proposing a sweeping overhaul of the tax code is to bring that rate down to 35 percent.

The Environmental Protection Agency has concluded that 403 highly toxic chemicals produced, sold and used throughout the United States would pose potentially serious health dangers to the public in a chemical plant accident. At least 577 companies at thousands of locations, including many in the New York metropolitan area, handle these chemicals, according to an analysis of chemical industry data by The New York Times. Some of these chemicals are produced and stored in the billions of pounds near populated areas, while some are so toxic that leaks of only a few pounds could cause injuries to people near plants, the agency said. The E.P.A. list and its associated documents, obtained from Government officials, are the first major step in a Federal effort to measure the potential for toxic chemical accidents. The documents, which took months to prepare, explain how municipalities can determine whether these chemicals are handled in their midst, and offer suggestions for minimizing the prospects of major chemical accidents like the one in Bhopal, India, last December that killed more than 2,000 people, and one in Institute, W.Va., Aug. 11 in which leaking chemicals injured six plant employees and 135 area residents.

WITHOUT trying to put words into Charles Dickens's pen, it is a good guess he would have known exactly what to write about the coming college basketball season. ''It was the best of times,'' we can picture the old chronicler noting, ''it was the worst of times.'' Rollie Massimino said it another way. ''I'm happy,'' said the Villanova head basketball coach, ''and I'm sad.'' Massimino was responding to a question about the 1985-86 season, which, on its most general terms, is post-Patrick Ewing and post-Tulane.

When the domestic car makers closed the books on the 1985 model year recently and tallied their sales, they found that the best-selling car in the United States was a truck - Ford's F-Series full-size pickup. The second best seller was also a pickup - Chevrolet's C-Series. ''Trucks have captured the imagination of the American public,'' said one new-car dealer. New models, sleeker styling, greater comfort, more options, better fuel efficiency and lower prices than some compact cars have transformed the once useful but unglamorous vehicle into an attractive option for personal transportation.

Shortly before he assumed the chairmanship of the Anglo American Corporation of South Africa, this country's biggest mining and industrial conglomerate, Gavin Relly was asked about his relationship with his predecessor, Harry Oppenheimer. As chairman, a reporter inquired, would he feel obliged to emulate the kind of public position established by Mr. Oppenheimer? Mr. Oppenheimer's father, Sir Ernest Oppenheimer, founded South Africa's greatest corporate dynasty almost 70 years ago, and the son's style fused the politics of opposition with the business of creating fortunes in gold and diamonds. ''One shouldn't make the mistake,'' Mr. Relly replied, ''of thinking it's my job now to fill Harry's boots in an image sense. I don't intend to have to fill his boots. I intend to fill my own.''

Walter Payton ran for 132 yards. The Refrigerator played fullback and ran for a yard. The Chicago Bears won again. Routine stuff? Forget it. The Bears' remarkable season rolled on today with their most emphatic victory of the year, 44-0 over the Dallas Cowboys. The triumph gave them an 11-0 record and a host of other residuals: * The Bears became the first team this season to clinch a division title and the earliest to do so since the National Football League expanded its regular-season schedule to 16 games in 1978. They also became the first National Conference team to win its first 11 games. * The victory broke a six-game losing streak to the Cowboys, which began after the Bears won in 1971, when Mike Ditka, the Bears' coach, was a backup tight end for Dallas.

Although securities dealers do not expect to sell this week's heavy supply of new Treasury issues at the low yields that prevailed early last week, there is widespread optimism among investors, economists and traders that the new issues can be absorbed without any sizable rise in interest rates. The supply of Treasury notes and bonds is extraordinarly heavy this week because delays in raising the Federal debt ceiling caused the Treasury to postpone many financings. Notes and bonds totaling $32 billion are to be sold this week, followed by $7.5 billion next week. ''There has been no change in the fundamentals, which are that everybody wants interest rates lower for the sake of the economy and to bring down the dollar,'' said Samuel Thorne, senior vice president at Scudder, Stevens & Clark Inc., an investment advisory firm. He acknowledged that ''there is some disappointment'' over the absence of the Gramm-Rudman amendment, which requires automatic cuts in Federal spending if the budget did not move toward balance. But the dominant fact of life in the credit markets remains ''the obdurate sluggishness of the economy,'' Mr. Thorne said.