What was going on when I was born?

The nation's major banks cut their prime rate half a percentage point yesterday, to 9 1/2 percent. This is the first time the benchmark lending rate has been below 10 percent since 1978. The drop in the prime rate, to which many loans in the United States and abroad are tied, is expected to stimulate the nation's economy. Also businesses, individuals and debtor nations that are carrying an immense amount of floating-rate debt should find it easier to repay their loans.

Intensifying its effort to combine personal computers with more sophisticated office equipment, the International Business Machines Corporation said yesterday that it would begin selling a new version of its leading minicomputer through some computer retail stores. The move marks the first time that I.B.M. has allowed retailers to market products previously reserved for I.B.M.'s own sales force. Until now, those stores have sold only I.B.M. Personal Computers, and the computer giant's own internal sales force has staunchly resisted efforts to broaden the retailers' offerings, saying it could not compete with retailers' discounts.

An article in Weekend Friday about picking strawberries gave an incorrect telephone number for the Blue Jay Orchards in Bethel, Conn. The number is (203) 748-0119.

President Reagan, vowing that the United States would never give in to terrorists, called tonight on Lebanese Shiite hijackers to release their American hostages without conditions. Speaking at a nationally televised news conference, he said: ''American will never make concessions to terrorists. To do so would only invite more terrorism.'' Then, in an obvious reference to Israel, he added, ''Nor will we ask nor pressure any other government to do so.'' The hijackers of the T.W.A. jet, seized Friday, have called for the release of 700 Lebanese Shiites detained in southern Lebanon and now being held in Israel.

WEDNESDAY, JUNE 19, 1985 International The hostages' unconditional release was called for President Reagan. He vowed that the United States would never give in to terrorists. In a nationally televised news conference, he said ''American will never make concessions to terrorists. To do so would only invite more terrorism.'' He urged an extension of the American ''armed sky marshal program'' to international flights of domestic airlines. [Page 1, Column. 6.] Three more hostages were freed in Beirut by the hijackers of the Trans World Airlines jet. Two Americans and a Greek were released. About 40 other Americans were still being held, and there was no indication that talks to free them were near. [A1:3.]

SOUP and a sandwich, for many people, is the most comforting meal imaginable. On a cold winter night, with the wind dashing sleet against the windowpanes and a crackling fire burning on the hearth, there is nothing more satisfying than a bowl of hot soup, accompanied by a hearty sandwich, preferably made of toasted bread. Well, it works in the summertime too. On a steaming summer night, when the air-conditioning has broken down and all the windows are open to catch whatever breeze might stir the listless air, there are few things more refreshing than a well-chilled bowl of cold soup, elegantly garnished and accompanied by a freshly made sandwich, including sliced seasonal vegetables. Cold soups are an easy solution for the busy summertime cook, whether working person or parent occupied with young children out of school for the duration. For the vacationing cook, they are ideal: Soup can be prepared in the cool, early morning hours and set in the refrigerator to chill while the cook takes off for a day at the beach. The fresh fruit or berry soups that are traditional summer fare in Scandinavia are a pleasant change, or try the fruit gazpacho.

WEDNESDAY, JUNE 19, 1985 The Economy The nation's major banks cut their prime lending rate by half a point, to 9 1/2 percent, putting the rate below 10 percent for the first time in seven years. Many loans, both in the U.S. and abroad, are tied to the prime, so the drop should stimulate the economy, which has virtually stagnated since last summer, especially in such sectors as farming and manufacturing. Many economists say the prime rate could drop further in coming months. [D1.]

The Army says there has been an increase in reports of attempts by Soviet and other Eastern European intelligence services to recruit American soldiers as spies. In interviews, Army officers said there were 481 incidents last year in which soldiers reported being approached by people they suspected of being Soviet or East European intelligence officers, or by sympathizers in nations such as West Germany. That was a 400 percent increase over 1978, the officers said. Of those, they said, 94 cases were referred to Army counterintelligence for possible action. That would include having the American soldier act as a double agent to obtain information from those who had recruited him.

An article in Business Day yesterday about 29 firms interested in becoming primary dealers in British Government securities incorrectly reported the number of primary dealers in United States Government securities. There are 36 such dealers, according to the Federal Reserve Bank of New York.

Housing starts fell a surprisingly sharp 14 percent last May, to an annual rate of 1.66 million units, the Commerce Department reported today. Industry executives, however, said no one had expected the brisk April rate of nearly 2 million starts a year to be sustained. They also said the continuing slide in mortgage interest rates since the May figures were compiled bodes well for higher figures in the months ahead.

The House of Representatives voted tonight to bar the purchase of any additional MX missiles next year and to limit deployment of the intercontinental weapon to a total of 40. The vote was another setback in the Reagan Administration's struggle to keep the MX missile alive. Last month, the White House reluctantly accepted a proposal in the Senate that would allow the purchase of 12 new missiles in the fiscal year beginning Oct. 1 and limit the operational force to 50 weapons. The Senate voted this limit last month. 'We Need It,' Reagan Says The details of a final compromise will be settled by a House-Senate conference, but today's vote made it clear that both houses of Congress want to place tight restrictions on the MX program and end the decade-long debate over the missile. At his news conference tonight, President Reagan repeated his support for the MX missile and said it was vital to the modernization of America's strategic force. ''We need it,'' he said.

TO most of us, mosquitoes and ticks are just seasonal annoyances, the price we pay for enjoying the outdoor pleasures of summer. But these bloodthirsty creatures can be more than just ordinary pests. They are the bearers of serious illness, vectors for encephalitis, Rocky Mountain spotted fever and Lyme disease. Changes in Americans' travel habits and in the recycling of such things as old tires, favorite breeding places for mosquitoes, are spreading these once-localized diseases, putting many people at risk. Encephalitis, although not the devastating threat that malaria and yellow fever still are in some parts of the world, is sometimes fatal. There were 138 confirmed cases of encephalitis last year, and 1 death, according to the Federal Centers for Disease Control. There were 1,126 cases of Rocky Mountain spotted fever in the first half of 1983, with about 45 deaths, while 1,000 to 2,000 cases of Lyme disease were reported in 1984. Lyme disease has yet to prove fatal but, along with encephalitis, it can have long-lasting debilitating effects.