What was going on when I was born?

The heads of several predominantly black colleges threatened today to remove them from the National Collegiate Athletic Association because of a new rule requiring athletes to achieve a minimum score on college entrance examinations. The schools are among 16 largely black colleges that are members of the N.C.A.A.'s Division I, the major division. They also threatened to quit the American Council on Education, which backed the N.C.A.A. position. The minimum-score requirement was enacted Tuesday at the N.C.A.A. convention here by the 277 schools in Division I. It was intended, its proponents said, to stem increasingly frequent charges that some of the nation's major athletic colleges were exploiting talented student-athletes.

''It has been a privilege to serve as director of the Arms Control and Disarmament Agency for the past 20 months.

The Dow Jones industrial average, the stock market's most widelyfollowed barometer, yesterday finished barely lower after piercing the 1,100 level for the first time in its history earlier in the session. After opening higher, the blue-chip indicator moved upward and reached its peak for the session at 2:30 P.M. when it was up 16.28 points at 1,100.07. However, the 30 components of the Dow then succumbed to a wave of selling by investors cashing in profits and closed down 0.18 point to 1,083.61. In the previous four sessions, the Dow average climbed 40 points, which included a loss of 8.56 points on Tuesday.

The guards who had been held hostage at the state prison here for 53 hours thanked those among their captors who protected them today, saying the action ''will not soon be forgotten.'' In a meeting with newsmen at Phelps Memorial Hospital Center in nearby North Tarrytown, one of the corrections officers, John McNamara, asked that they be allowed ''only to return to our loved ones.'' They turned and filed off the stage, and within an hour, according to hospital authorities, all of them had been discharged. They had been undergoing psychological evaluation.

An obituary of the pianist William Harms yesterday incorrectly named the college where he taught. It was Manhattanville, in Purchase, N.Y.

A Federal appeals court today overturned a $1.8 billion antitrust award levied against the American Telephone and Telegraph Company for trying to monopolize the long-distance telephone market. But in a 2-to-1 decision of 205 pages, the United States Court of Appeals for the Seventh Circuit agreed that there had been antitrust violations by A.T.& T. against the MCI Communications Corporation and ordered a new trial to set damages. MCI is A.T.& T.'s largest competitor in the long-distance telephone market. The ruling threw out a 1980 District Court jury verdict that awarded $600 million to MCI. That judgment was later trebled, as permitted under antitrust law.

President Reagan announced today that he would nominate Margaret M. Heckler, a former Representative from Massachusetts, to succeed Richard S. Schweiker as Secretary of Health and Human Services. If confirmed by the Senate, Mrs. Heckler would head the largest Cabinet department, which spent more than $275 billion last year. In her bid for re-election last fall in a reapportioned district, Mrs. Heckler was defeated by a Democratic incumbent, Representative Barney Frank, who portrayed the election as a referendum on President Reagan's economic and military policies. Mr. Reagan also announced today his intention to nominate John A. Svahn, the Commissioner of Social Security, to be Under Secretary of Health and Human Services. Mr. Svahn, who is 39 years old, served as director of the California Department of Social Welfare when Mr. Reagan was Governor in the early 1970's. If confirmed as Under Secretary, Mr. Svahn would succeed David B. Swoap, who returned to California this month to join the Cabinet of the state's new Republican Governor, George Deukmejian.

For executives in the mass-market paperback book industry, it's just one problem on top of another. Some say their total reading public has declined. Consumers are balking at higher prices. The surging popularity of romance novels, while good for revenues, has created retail bottlenecks. In balance-sheet terms, the problems have been showing up as generally flat net unit sales for several years with a slight slippage in the first 10 months of 1982 - though strong Christmas sales were reported - and modest gains in revenues. And some executives of these paperback companies, whose products include mystery novels, how-to books and celebrity confessions, are voicing concern.

For Tom Schmidt, director of operations at Burlington International Airport, the proof is in the parking lot - there is not enough space these days. Since Nov. 15, 1982, when People Express brought its low fares and no-frills service here, the airport parking lot has been overflowing virtually every day, and expansion plans are in the works. ''This is an example of deregulation at work,'' said Mr. Schmidt, who is leaving Burlington this month for an airport post in Las Vegas, Nev. Passenger boardings here set a record in December, he said, and ran about 50 percent above the December 1981 level. Burlington, a city of fewer than 40,000 people, today is served by seven air carriers: USAir, Air Florida, People Express and four smaller commuter lines.

Because of a mechanical error, some copies of the Late Edition yesterday carried page C17 twice and omitted page C19, which included the Going Out Guide. Readers wishing copies of the missing page may write to Production Quality Control, The New York Times, 229 West 43d Street, New York, N.Y. 10036.

Treasury Secretary Donald T. Regan pledged today that the Adminstration would not propose major tax increases this year or next. At the same time, some officials suggested that reductions could be proposed in President Reagan's military budget in the years after 1985. However, Mr. Regan, according to aides, continued to work on a package of more than $100 billion in contingency tax increases over three years that would become effective in the fiscal year 1986 if Federal deficits were not declining sharply enough. The developments came amid a flurry of activity as the Administration tried to put together the budget for the fiscal year 1984, which must get to the printer in the next few days if the President is going to meet his deadline of Jan. 31 for sending it to Congress.

President Reagan dismissed Eugene V. Rostow today as director of the Arms Control and Disarmament Agency and said Secretary of State George P. Shultz would play the principal role in coordinating the Administration's arms control policies. As part of an overall shuffle in the management of arms control matters, Kenneth L. Adelman, the No. 2 official in the United Nations Mission, was chosen to replace Mr. Rostow as the head of the disarmament agency. David F. Emery, who was a Republican Congressman from Maine until he lost in the Senate election last year, was picked to be Mr. Adelman's deputy. Morton I. Abramowitz, a career Foreign Service officer, was chosen to be the new envoy to the negotiations in Vienna on East-West conventional force reductions. He will replace Richard Starr, whose resignation was demanded by the Administration.