What was going on when I was born?

The CSX Corporation, the nation's leading coal-hauling railroad, announced yesterday that it would take a write-off of nearly $1 billion against fourth-quarter earnings as part of a major corporate realignment program. The one-time pretax write-down will probably result in a loss for the year. CSX, which was formed through the 1980 merger of the Chessie System and Seaboard Coast Line Industries, earned $465 million in 1984.

Helped by a string of developments that could aid businesses for years to come, the Dow Jones industrial average demolished the stubborn 1,500 barrier yesterday in the fifth-busiest session in Wall Street history. More than 178 million shares traded on the New York Stock Exchange, just a day after House and Senate conferees approved a bill intended to shrink the Federal deficit until the Government's budget is balanced by 1991. When the Government spends less, it needs to borrow less, and according to Wall Street analysts and economists, this would lead to lower interest rates in the future and better corporate profits. With that in mind, investors yesterday stampeded into the equities market, sending the Dow up 12.50 points, to a record close of 1,511.70. The blue-chip average of the stocks of 30 of the biggest United States companies had briefly exceeded the 1,500 level on several occasions in the last few weeks but never finished above it.

Twenty-four workers were exposed to small amounts of radioactive gases at the Oyster Creek nuclear power facility in southern New Jersey yesterday after electricity to a ventilation system was interrupted, the utility reported. Officials of the Jersey Central Power and Light Company, which operates the plant, said the amount of radiation released was ''minuscule'' and that there was no danger to the public or to the reactor at any time. A spokesman for the Federal Nuclear Regulatory Commission said that a small amount of contaminated gas was released into the atmosphere but that, based on information from the utility, it was ''a very small amount within our limits.''

Indicating that the Pennzoil Company wants to avoid a prolonged court fight, J. Hugh Liedtke, the company's chairman and chief executive, said today that he would consider a transfer of assets by Texaco Inc. to Pennzoil to settle the $11.1 billion judgment entered against Texaco Tuesday. ''I'm not saying for sure that we would in fact agree to it, but it certainly is something we would consider,'' Mr. Liedtke said during an interview at Pennzoil's headquarters here. He said lawyers for Pennzoil and Texaco were ''in contact'' today, but declined to provide details of the discussions. He did say, however, that shortly before the decision on Tuesday Texaco had proposed a settlement involving the sale by Texaco of oil to Pennzoil.

''Perhaps the single most pivotal factor in the commission's determination that boxing should be abolished is its investigative conclusion that not even the sturdiest of statutory controls will reduce the brutality of the sport to any significant degree.

TWELVE parents sat in a circle during the first ''He-Man Workshop'' at the Christ Church Day School in Manhattan and voiced their concerns - and confusions - about the state of children's television entertainment. ''I'm worried about the one-dimensional nature of the characters,'' said the father of one of the school's 90 children between the ages of 2 and 5. He was referring to ''He-Man and the Masters of the Universe,'' the popular half-hour weekday animated children's television show. ''Why can't an all-powerful hero have a sense of humor too?'' he asked. ''And yet, somehow I feel this Superhero play is important,'' said the mother of a 4-year-old. ''Isn't it just a modern version of 'The Odyssey'?''

In a striking setback for President Reagan, the House of Representatives voted today to block consideration of tax revision legislation, the top legislative priority of the President's second term. Democratic leaders, working with the White House, toiled tonight to revive the measure for a vote before Congress adjourns, probably by the end of the week. But the Democrats said today's vote indicated that tax legislation could not pass unless Mr. Reagan could round up more Republican votes for it. If the President ''cannot deliver the votes in a forthwith manner, the bill is dead,'' said Thomas P. O'Neill Jr., the Speaker of the House. Conferring With Reagan The White House, apparently taken by surprise by today's outcome, was said tonight to be trying urgently to win the support of Republican lawmakers. ''It ain't over till it's over,'' said Treasury Secretary James A. Baker 3d.

VIVIAN and Martin Lorber live in a four-bedroom house on a Florida beach. Thea and Terence Nolan live in a two-bedroom apartment on Manhattan's East Side. Susan Schulman lives with her family in a 13-room town house on the West Side. And Jane Nielsen lives in a one-bedroom apartment with a spectacular river view from downtown Manhattan. Their living styles and their homes are all different, but they have one thing in common: They were decorated by the interior design services of Manhattan department stores.

The Economy Congress approved legislation aimed at shrinking the deficit to zero by 1991. The Senate approved the bill on a 61-to-31 vote. Then the House passed it on a 271-to-154 vote and sent it to the White House. President Reagan has said he would sign the bill despite reservations about its effect on the military budget. [Page A1.] The House voted to block consideration of tax revision in a striking setback for President Reagan. Democratic leaders, working with the White House, later worked to revive the measure before Congress adjourns. But they said legislation could not pass unless Mr. Reagan rounds up more Republican votes. [A1.] Startled White House officials tried to figure out where they went wrong and to make plans to salvage some form of tax revision. [A1.]

One of the most abrupt Congressional setbacks of Ronald Reagan's Presidency left startled White House officials trying to figure out where they went wrong and making plans late today to salvage some form of tax revision, the major legislative priority of Mr. Reagan's second term. The House defeat marked an uncharacteristic lapse for White House legislative strategists who had not gauged the depth of Republican opposition and did not make full use of Mr. Reagan's persuasive powers. Paradox for Reagan Moreover the blocking of consideration of the tax legislation, which may turn out to be temporary, came as Congress moved to endorse a budget-balancing proposal that, Administration officials concede, threatens key portions of Mr. Reagan's legislative agenda, including military programs. This put Mr. Reagan in the paradoxical position of losing a key vote on legislation that he regards as central to his legacy while a budget-balancing bill about which he has serious reservations continued to move ahead.

International The Philippine opposition agreed that Corazon Aquino would run for President with her chief rival, Salvador H. Laurel, as her running mate. The compromise was worked out one hour before the expiration of a midnight filing deadline. The slate will face President Ferdinand E. Marcos in elections scheduled for Feb. 7 under the banner of Mr. Laurel's party. [Page A1, Columns 2-3.] Assertions that President Marcos and his wife, Imelda, have accumulated extensive real estate and other holdings in the United States are the subject of House subcommittee hearings that started yesterday. [A15:1.]

An article on the Washington Talk page Tuesday about William McChesney Martin, the former Federal Reserve chairman, erroneously described the rarity of Government buildings named for living people. The General Services Administration says that a cursory check shows about 20 Federal Government buildings in various states named for people still living, including former Senator Jacob K. Javits of New York, Representative Peter W. Rodino Jr. of New Jersey and former Senator and Secretary of State Edmund S. Muskie of Maine.