What was going on when I was born?

The purchase by the Plessey Company P.L.C. earlier this month of a stake in Scientific-Atlanta Inc., the American cable television and satellite-equipment concern, is small beer, as far as American acquisitions go. The deal will amount to $114 million, at most. But coupled with Plessey's purchase last fall of part of another American technology concern, the Stromberg-Carlson Corporation, it is being seen here as a major corporate step. The two investments leave little doubt that Britain's largest telecommunications company is pinning its hopes on the American market to confront the challenges of deregulation at home and in the United States.

Astor, the Bronx Zoo's mischievous, inquisitive baby elephant, who charmed children and their escorts with his high-pitched cries and ear-flopping romps through the Wild Asia area, has died, apparently of heart disease. He was 17 months old.

Wall Street economists gave President Reagan's budget mixed reviews yesterday. On the one hand, analysts were pleased with Mr. Reagan's recognition of the economic threat posed by rising Federal budget deficits and the economic projections upon which those figures were based. On the other, they said the size of those deficits, and the prescriptions offered to cope with them, did not offer much hope for the future. ''This budget is a mixed blessing,'' said David Jones, chief economist at Aubrey G. Lanston & Company, a Government securities dealer. ''Unlike a year ago, we have a budget deficit which is at least based on realistic economic assumptions. But the arithmetic of the deficits still threatens to overwhelm the financial markets.''

With his budget for the fiscal year 1984, President Reagan is declaring that the enormous Federal deficits ahead cannot be reduced without help from some of his severest critics in Congress. Thus, Mr. Reagan is proclaiming a new era of bipartisanship that White House officials say could clear the way for significant revisions of the budget by Congress in the areas of taxes, military spending, domestic spending and jobs programs. Since the November elections, when the Republicans lost 26 seats in the House, a certain amount of Congressional tinkering with Mr. Reagan's next budget has been regarded as inevitable. This became clearer as Republican leaders in the Senate signaled their independence in recent weeks. As described by Mr. Reagan's aides, the goal of the budget makers this year was to produce a realistic plan that could serve as a framework for discussion on Capitol Hill and guarantee that Mr. Reagan would be the major player in those discussions.

President Reagan, in an open letter read here tonight by Vice President Bush, called on Yuri V. Andropov, the Soviet leader, to meet him to sign a treaty banning all intermediaterange, land-based nuclear missiles. Addressing the people of Europe, Mr. Reagan's message said he would meet with Mr. Andropov ''whenever and wherever he wants'' to conclude an agreement totally eliminating the weapons. ''I make this offer,'' the President said, ''out of the conviction that such an agreement would serve the interests of both sides, and, more importantly, that the people of Europe want nothing more.'' (In Washington, a deputy White House press secretary, Lyndon Allin, said Mr. Reagan was not making a new proposal but was simply stating a willingness to sign a pact with Mr. Andropov if the Soviet Union accepts the United States so-called zero-option proposal. (In Tokyo, Secretary of State George P. Shultz told Prime Minister Yasuhiro Nakasone that the United States would never negotiate an agreement on reducing medium-range missiles in Europe at the expense of Japan's security. Page A9.)

THE fastest computers in the world are today built in the United States, but these symbols of American ingenuity may soon be found only in museums. The Japanese Government last year unveiled a $200 million program aimed at cornering the world market in supercomputers with machines 1,000 times more powerful. Predictions of an American decline are voiced by academicians and scientists who fear that the race for supercomputers of the future may be somewhat lopsided. The Reagan Administration, ignoring calls for an expensive crash program, has invoked the magic of the marketplace and the genius of lone inventors. The stakes in the gamble are high. No computer is now powerful enough, for example, to simulate the airflow around an entire aircraft, so aerodynamic designs are often put together in piecemeal fashion or by the repeated processing of two-dimensional slices. The first country with computers that can design the plane as a whole, according to a recent report of the National Science Foundation, ''will undoubtedly produce planes with superior performance.'' So too, the Government wants bigger supercomputers for building better weapons, breaking codes, and developing new sources of energy.

The Gulf Oil Corporation said yesterday that it was lowering the price it would pay for domestically produced crude oil by $1 a barrel, to $31 for its standard grade. The move was attributed to widespread expectations that the price of oil will decline on the international market. Gulf's move followed a similar $1 reduction on Dec. 8. The reduction by the nation's fifth-largest energy concern was expected to be followed by other major oil companies and could lead to lower prices for refined products such as gasoline and home heating oil.

President Reagan, urging the nation to ''face the future with the Bible,'' received repeated standing ovations from a convention of Christian broadcast preachers today. He vowed to renew his efforts for a ban on abortion, for restoring classroom prayer and for tax credits for parochial school tuition. With his budget proposal finally delivered to Congress after a difficult period of revision and controversy, Mr. Reagan made a point of emphasizing other major topics today, including the social issues and the disarmament campaign. As Mr. Reagan addressed the broadcasters, Vice President Bush was carrying a letter to Europeans in which the President vowed to meet the new Soviet leadership on the missile issue.

''As a kid, they always came to me and said you're the best drummer, but we have to make Bobby the drum sergeant because you're a girl.

ANEW law denying Federal grants and loans to students who have failed to register for the draft has produced conflict between the Federal Government and some of the country's leading colleges and universities. The University of Minnesota has announced plans to challenge the constitutionality of the law, as have several Quaker colleges. Some have devised plans to make up for any aid that students lose because of it. Student groups also said last week that they plan to lobby for changes in the legislation. ''The requirement is unnecessary, unconstitutional and discriminatory,'' said Miriam Rosenberg, national director of the National Coalition of Independent College and University Students. ''We plan to do whatever we can to repeal this provision.''

Governor Cuomo proposed a $31.5 billion state budget today that would cut 14,000 jobs from the state payroll to help close a deficit he put at $1.8 billion. He also suggested tax increases and other measures to increase revenues by more than $900 million in the next fiscal year. ''The pain in the budget must be diffused and shared,'' Mr. Cuomo said as he outlined his plans for the 1983-84 fiscal year. Mr. Cuomo said he had lived up to campaign commitments in two key areas - avoiding increases in business and income taxes and in the amount of the sales tax, and providing $359 million in Medicaid costs for New York City and county governments across the state. But to do this, he proposed measures that would increase the costs of making a long-distance telephone call, getting a driver's license and owning a car, buying cigarettes and other tobacco products, getting a haircut, going to the theater or the movies, and attending a state- or city-run college.

A plan designed to bring New York City's air quality into compliance with national standards was described as inadequate yesterday by the Federal Environmental Protection Agency. The agency named 144 areas in 31 states it said had failed to meet the goals of the Clean Air Act on time, and listed 16 states besides New York whose plans might be disapproved. The finding is a tentative one, and gives state and local agencies time for comment or to make new proposals for reducing ozone and carbon monoxide in the air. ''New York's plan is, we believe, inadequate,'' said Jacqueline E. Schafer, regional administrator of the agency.