What was going on when I was born?

Israeli forces dug in on the hills of this resort town east of Beirut today as armored units continued to isolate Beirut from the rest of Lebanon. In addition to fortifying their hilltop vantage points, from which they overlook Syrian encampments in a valley below as well as Beirut in the distance, the Israelis have reportedly captured the science campus at Lebanese University in Shuweifat. The campus has strategic value because it is close to Palestinian refugee camps and the international airport, which has been out of operation since the Israeli invasion began June 6. And Wafa, the Palestinian press agency, said tonight that the Israeli attack on the campus had been repulsed.

When Michael Forrest first told his parents he wanted a computer for his 11th birthday, they did not take him seriously. ''We thought, 'He wants a computer - ha, ha,' '' said his mother, Esther Forrest of Great Neck, L.I. ''But then, when we really investigated prices, we found it's not so bad.'' So the Forrests bought Michael a $300 Commodore VIC-20 computer. Indeed, people like the Forrests, whether buying for their children or themselves, are proving that the age of home computers is finally arriving. The products of Commodore International, Atari Inc., Texas Instruments Inc. and the Tandy Corporation's Radio Shack are finding their way into the American home. ''We're watching the real birth of the home computer,'' said Egil Juliussen of Future Computing Inc., a market research firm in Richardson, Tex.

A detailed drawing guides weavers of Oriental rugs through the intricacies of design. And faced with the complexities of today's market, many consumers might welcome a similar master plan to help them sort out the vast array of modern Oriental rugs, in terms of country of origin, type of weave, pattern and price. Not that Oriental rugs are novel. They have been woven for thousands of years and have been imported for American homes ever since the mid-19th century. But the political revolution in Iran and the commercial revolution in United States-Chinese relations have caused a merchandising revolution in Oriental rugs. Until the early 1970's, the market was dominated by pile rugs in Persian designs from Iran. Now, rugs in Persian designs come from many countries, primarily from India and Pakistan. Chinese rugs have become a major factor in the market, and the options have been further extended by the fashion for nonpile or flat-weave rugs, known as kilims and dhurries. Kilim is the generic term for any flat-weave rug, and a dhurrie is a type of kilim made only in India. ''A new market in Orientals has been developing for the past several years,'' says Mason Purcell, who is president of the Oriental Rug Retailers of America and a rug dealer in Charlottesville, Va.

Lewis E. Lehrman, a multimillionaire who challenged the established leaders of the Republican Party, won the party's designation for Governor of New York yesterday. Mr. Lehrman got 68.88 percent of the weighted votes at a hectic meeting of the Republican State Committee in Manhattan after a day of confusion and a series of nighttime surprises. Thus, a candidate who had proclaimed his status as an outsider in a series of radio and television commercials became the official party choice. He will be in a primary contest against Paul J. Curran, a former United States Attorney for the Southern District of New York.

An obituary of Edwin J. Beinecke Jr. on Monday incorrectly described his position with the Sperry & Hutch- inson Company. He had been chair- man of the executive committee.

Reagan Administration officials said today that the United States had been reassured by Israel that its troops would not seize Beirut. This, they said, insured that President Reagan would meet with Prime Minister Menachem Begin. The meeting had been in doubt after remarks by State Department officials on Tuesday that the talks might not take place if the Israeli troops poised outside the Lebanese capital moved into the city. With Mr. Begin in New York to address the United Nations special session on disarmament, Secretary of State Alexander M. Haig Jr. telephoned him to arrange to meet with him on Friday morning.

Housing starts rose 22.3 percent in May, to an annual rate of 1.09 million, the Commerce Department reported. It was the first time since last July that the figure had exceeded 1 million. Analysts attributed the May increase to a surge of housing construction in the South, to greatly increased construction of condominiums and to increased Federal construction activity. (Page D1.) Manufacturers operated at just 70.8 percent of capacity in May, the Federal Reserve Board reported. The rate was the lowest in seven years, although the monthly decline of two-tenths of 1 percent was smaller than those in the previous two months. (D7.)

An article June 3 about the history of United Press International incompletely described its policy on rates. Although the news agency says it offered some newspapers and radio stations cut-rate prices in the past, it adds that its rates have been uniform since 1979 and that 25 newspapers have become subscribers this year.

Two decades after the Castro Government openly embraced socialism, the slump in world sugar prices has brought an uncomfortable reminder of Cuba's continuing economic dependence on the West. Although two-thirds of its sugar is sold to the Soviet bloc, Cuba needs sales on the open market to maintain its lifeline to hard currencies. And with sugar accounting for 80 percent of its total exports and a sharp decline in the world price, the shortage of foreign exchange is pushing the Cuban economy into a slump. ''Cuba remains as dependent on sugar as it was in 1960,'' said a Latin American economist who asked not to be identified. ''Its fortunes rise and fall with the Western price of sugar. And now they have fallen.''

Housing starts rose 22.3 percent in May, to an annual rate of 1.09 million, the Government reported today. It was the first time since the start of the recession last July that the figure exceeded 1 million. The report by the Commerce Department said that the increase from April's seasonally adjusted annual rate of 888,000 units had brought the rate to its highest level since the 1.17 million of May 1981. Separately, the Federal Reserve Board reported that the nation's manufacturers ran their factories at only 70.8 percent of capacity last month, the lowest rate in seven years. May's drop of two-tenths of 1 percent in factory use was the ninth decline in the past 10 months. (Page D7.)

The merger guidelines that the Justice Department issued this week provide little actual guidance on which mergers will pass legal muster, many antitrust experts say. Despite the adoption of the Herfindahl index, a mathematical standard to measure market concentration, they say the guidelines neither address the practical problems of merger law nor change the department's enforcement policy to any significant degree. In fact, several former heads of the department's antitrust division agree that the 44-page guide put out on Monday by their successor, William F. Baxter, are more a reflection of his background as an economics professor than an aid to those who must counsel corporate clients on the lawfulness of proposed acquisitions. ''It is largely an economic treatise on standards that aren't very dissimilar from what went before,'' said Sanford Litvack, a former antitrust chief who now practices law in New York. ''The guidelines give you the illusion of telling you something that in reality is going to have to be fought out in court.''

Britain warned today that hundreds of Argentine prisoners of war in Stanley could die from hunger soon unless their country pledges to cease all hostilities over the Falkland Islands. Rear Adm. John F. Woodward, commander of the British task force that retook the islands on Monday, said in a Surrender text is on page A16. statement issued here that many of the captives - whose number was put at 15,000, far more than London had expected - were seriously ill with maln@utrition, dysentery and scabies, a parasitic skin disease. He said there was no shelter for most of them from the blizzards and frequent subzero temperatures in the Falklands.