What was going on when I was born?

The House of Representatives adopted a compromise proposal tonight that would keep the MX missile in the nation's arsenal but in a significantly reduced and restricted form. The vote, on a major amendment, was 229 to 199. Earlier, in a test vote, the House defeated an attempt to eliminate all financing for the construction of new missiles in the fiscal year beginning Oct. 1 - $2.7 billion for 30 missiles. With the outcome in doubt until the final seconds, that amendment lost by 218 to 212. The winning tally in that vote included 146 Republicans and 72 Democrats. Only 18 Republicans defected from President Reagan and joined 194 Democrats in voting to knock out the entire amount.

It was exactly 100 years ago today - in the days when the streets of New York were filled with gas lamps and horse-drawn carriages - that a wealthy young woman named Elizabeth H. Cullum stood at the upper reaches of Central Park and unveiled the cornerstone for a structure that would change the direction of health care. On that day Mrs. Cullum, a cousin of Mr. and Mrs. John Jacob Astor, dedicated the foundation for the New York Cancer Hospital, the forerunner of the Memorial Sloan-Kettering Cancer Center and the first hospital in the country to be designed exclusively for the treatment and cure of cancer. To celebrate that event, a United States postage stamp is being issued today to honor health research. And at the precise moment - 4 P.M. - that the old cornerstone was unveiled. the institution will conduct academic ceremonies for this year's graduate students.

A GROWING number of small specialty shops have been springing up in Manhattan. These emporiums, with a sense of their own style, offer a new and enticing array of home furnishings, practical and fanciful, affordable and extravagant. The shops, several of which have opened in recent weeks, are situated around town from Madison Avenue to Chelsea. They provide browsers and shoppers with places in which to make discoveries. But each in its own way reflects a distinctive point of view and all are marked by the personal passions and longtime interests of their adventurous owners. Jehed Diamond practiced law; Andy Sichel was a painter. Both of them were interested in functional art. One day, the two friends came across a book on the early- 20th-century Omega Workshops in England. Omega had ''a painterly approach that was very concerned with showing the hand that made the piece,'' said Miss Diamond, who with Mr. Sichel decided to open a gallery and shop that would present objects that would ''break down the boundaries between crafts, architecture, fine art and design.''

The Reagan Administration has reportedly developed a plan to send some military equipment to El Salvador secretly through the Central Intelligence Agency. The plan, submitted this month, was blocked by the House Intelligence Committee, according to members of Congress and Administration officials. The lawmakers said the committee had objected on the ground that the plan appeared to circumvent aid limits set by Congress. The chairman, Representative Edward P. Boland, a Massachusetts Democrat, was reportedly angered and told William J. Casey, the Director of Central Intelligence, that the committee would not tolerate the shipments.

Senator Jesse Helms found himself in the center of a controversy among his Senate colleagues today as he vehemently denied that he had disclosed information from the Senate intelligence committee. The North Carolina Republican, a leading Senate conservative and an advocate of strong military forces, had been rebuked by Senator Barry Goldwater of Arizona, the chairman of the committee, and by Senator Daniel Patrick Moynihan of New York, the vice chairman. They accused Mr. Helms of disclosing committee information about covert election aid the Central Intelligence Agency gave to Jose Napoleon Duarte, the President-elect of El Salvador. Rebukers Are Challenged Mr. Helms challenged Senators Goldwater and Moynihan to substantiate their charges that he had violated the Senate rules by disclosing information obtained from the committee. The two Senators had made their charges in a letter of rebuke, hand-delivered to the Senate majority and minority leaders. Mr. Helms said no one had spoken to him about the charges.

Irwin Shaw, for more than 40 years a prolific and successful writer of short stories, plays, screenplays and novels - most notably the World War II saga ''The Young Lions'' - died of a heart attack yesterday in a hospital in Davos, Switzerland. He was 71 years old. Next to his bed at the time of his death was a copy of Thomas Mann's ''Buddenbrooks'' and a collection of Byron's poems. The author of a dozen novels - many of them best sellers - he was most admired for his short stories of the 1930's and 40's, which served as a model for an entire generation of writers. He was critically acclaimed for such early short stories as ''The Girls in Their Summer Dresses'' and ''Sailor Off the Bremen'' which began appearing in The New Yorker in the 1930's.

A report in the Company Briefs column of Business Day on April 28 misidentified the company signing a merger agreement with Jefferson Bankshares Inc. of Charlottesville, Va. It was the Citizens Trust Company of Portsmouth, Va.

Construction of new housing, rebounding from its sharpest monthly downturn in history, soared by 19.3 percent in April, the Commerce Department reported today. Although the figure seemed to signal a strong beginning for the second quarter, analysts cautioned that rising interest rates could soon dampen activity. The Commerce Department said construction starts for new homes and apartments surged to a seasonally adjusted annual rate of 1.96 million units last month, up from 1.65 million in March, marking the strongest improvement since a 26 percent rise in January 1983. The February rate was 2.26 million and the April 1983 rate was 1.55 million.

THERE are five garbage cans clustered in front of Sidney Thayer's ground-floor window on West 113th Street, a worrisome fact, though Mr. Thayer, an associate producer of sports films, shrugs it off: ''I have really clean neighbors. They tell me, 'Sidney, we always think of you when we take out our garbage.' '' Garbage cans aren't all that Mr. Thayer must put up with as a ground- floor tenant. Every time someone is buzzed into his building, or stops to jiggle a mailbox, or has a quarrel in the front entrance on the other side of his living-room wall, ''guess who gets to hear it all?'' he said. After three years at the low end of a brownstone, Mr. Thayer even admits to a sort of ground-zero neurosis. ''I can't help thinking now and then that I'm holding up the entire building, and that if anything ever happens they're all going to fall on top of my apartment.''

So how did I.B.M.'s Peanut go wrong? In the computer industry, explanations abound for why sales of I.B.M.'s smallest computer, the PCjr, are off to a disappointing start. But one theory gaining particular currency holds that the International Business Machines Corporation, the master of marketing, may have made a serious mistake by designing the Peanut for the $800-to-$1,600 price range. At that price, some analysts say, the machine is too expensive for casual home users, but, at the same time, is not nearly powerful enough for serious computer users who can afford a more capable machine. Thus, they say, the machine is betwixt and between, at once too much and not enough.

A financial rescue plan for the troubled Seabrook, N.H., nuclear plant will be based on a guarantee of much of the project's debt by the New Hampshire Electric Cooperative, officials said yesterday. Backers of the plan met in Washington yesterday with representatives of the Rural Electrification Administration in an attempt to agree on such a proposal, several sources said. A top official of the R.E.A., which currently backs the cooperative's Seabrook debt, said at midday that the agency was ''not about to be the guarantor'' for the debt of Public Service of New Hampshire, the nearly bankrupt utility that is the principal owner of the project. But last night Robert Hildreth, the Merrill Lynch Capital Markets executive who has proposed the rescue plan, said that ''things had changed'' and that ''there has been no decision one way or the other.'' Mr. Hildreth confirmed that the New Hampshire cooperative was the previously unnamed sponsor of the plan announced on Monday. And he said the R.E.A. was not being asked to guarantee the Public Service debt, only to support the desire of the New Hampshire cooperative to do so.

EACH year in New York, some children change schools. While most such changes take place among private schools, some parents elect the convenience of a neighborhood public school or others choose public schools offering special programs for the gifted, or in science and the arts. The most common reasons for such changes may be boredom with an undemanding curriculum, or poor grades, lack of friendships or a conflict with the school's philosophy. When the mismatch of child and school exists, the process of changing schools can be difficult. It can be a time of frustration or blame on the part of the parent and feelings of guilt and failure on the part of the child. Yet according to Margaret Corey, director of the Educational Records Bureau, an educational testing service for private schools that are situated in New York City, such feelings are unnecessarily pessimistic. ''A change in schools can be very positive and productive,'' she says.