What was going on when I was born?

The investment was huge and the risks enormous as the operators of cable television systems built their businesses over the last 10 years. After laying out hundreds of millions of dollars to wire American homes, they were still at the mercy of fickle consumers and regulatory constraints. Lately, though, there has been growing evidence that the cable system companies were on the right track. The Westinghouse Electric Company, parent of Group W Cable Inc., the nation's third-largest cable operator, has decided to cash in its investment by putting its system on the selling block. And the offering prospectus circulating among potential bidders discloses just how fast the picture can improve in cable - and how attractive an operation can be for others in the business who can benefit from economies of scale.

Mayor Koch issued a compendium of anecdotes, homilies, advice and insults yesterday, all stitched together and released in the form of his second book. In the new memoir, ''Politics,'' a sequel to the best-selling ''Mayor,'' Mr. Koch flits back and forth between his days in Congress, his political beginnings as a reform Democrat and the present. He reiterates his discomfort with ''richies'' and impatience with reformers. He tells candid tales about the powerful and even his late father. He uses expletives with abandon, lectures on racism, calls himself an ''anti-hero'' and repeatedly notes his love of combat.

In the face of solid opposition from the Republican leadership in the House of Representatives, President Reagan ''strongly'' urged the House to pass tax-revision legislation next week and send the bill to the Senate. The President did not wholeheartedly embrace the sweeping bill approved Tuesday by the House Ways and Means Committee, but he said House passage was the only way to keep the tax issue alive in Congress. Democratic supporters of the committee's bill said the House would probably pass the measure if the President reinforced his statement with an all-out effort to round up votes for it. Comment From an Aide Asked whether the President would do that, a White House spokesman said, ''The President will do what he thinks is necessary to keep the process going.''

President Reagan named Vice Adm. John M. Poindexter today to be the White House national security adviser, in a move the President said would allow ''continuity'' in foreign policy and national security issues. Admiral Poindexter, a career Navy officer who has been the deputy national security adviser since 1983, will replace Robert C. McFarlane. Mr. Reagan, flanked by both men in the White House press briefing room, announced Mr. McFarlane's departure at the same time that he named Admiral Poindexter to be the replacement.

Deutsche Bank A.G., West Germany's largest bank, plans to buy the country's largest family-held industrial enterprise, the Flick group, the two companies said today. A Deutsche Bank source said the takeover, which was initiated by Flick, would be worth about $1.8 billion, making it the largest takeover in West German history. After the purchase, expected before the end of the year, Deutsche Bank said it would offer shares in the Flick group to the public through a stock offering sometime next year.

The Economy President Reagan urged the House to pass the tax-revision bill and send it to the Senate, but Republican leaders in the House said they would work for the bill's defeat. Mr. Reagan called the committee's bill ''substantial progress from current law'' but said many elements need to be improved. Democratic supporters of the bill said it would probably pass the House if the President reinforces his statement with an all-out effort to round up votes. [Page A1.] The Cabinet recommended a revamping of antitrust laws, suggesting that the level of imports should become a statutory factor in determining whether a merger is lawful. [D2.]

''True tax reform is imperative. The first step must begin with a positive vote in the House of Representatives.''

In the 1955 novel ''The Man in the Gray Flannel Suit,'' this town served as the archetypical ''bedroom community'' for striving young executives with jobs in the New York City and children in school. But Tom Rath, the story's harried hero, no longer would need to depart each morning on the 7:40 train for the city. Instead, he could probably find work right here. Indeed, workers commuting to Westport now outnumber those leaving. Since 1972, commercial development here has nearly tripled - even though the population has remained at about 25,000 - and some residents are fearful of losing the small town charm.

With the number of homeless people in city shelters increasing daily, the Koch administration promised a state judge yesterday that it would provide 630 additional beds within 10 days to relieve overcrowding. The city acted after a record 8,239 people - 7,298 men and 941 women -crowded into city shelters early yesterday on the second night of a ''cold-weather emergency'' declared by Mayor Koch. At 1:30 A.M. yesterday, the temperature dropped to a low of 25 degrees, the second night of temperatures in the 20's. The emergency measures take effect when the temperature reaches 32 degrees. Last night the temperature dipped below freezing shortly after 10 o'clock but was not expected to fall below the high 20's. For tonight warmer weather with a chance of snow is predicted.

Stock prices exploded yesterday, under the pressure of demand that had been building for the last week. ''This was one of the best days of the rally,'' said Laszlo Birinyi, manager of equity market analysis at Salomon Brothers Inc. ''It's really giving people a lot of confidence in the market's ability to go higher.'' The Dow Jones industrial average gained 25.34 points, pushing it to a record close of 1,484.40. Traders and market analysts said that no single event was responsible for the buying binge. They speculated that investors who had been waiting for the market to retreat finally gave in and decided to join the equity-buying throng.

Imported automobiles claimed a near-record 32.4 percent share of the American car market in November, as domestic sales continued to decline after the ending of a major incentive program on Oct. 1. The import share record of 32.8 percent was set during the worst of the industry's sales difficulties in August 1982. In the Nov. 21-30 period, the domestic companies sold 184,506 new cars, a decline of 1.2 percent from 186,721 in the comparable 1984 period. There were eight selling days this year and last.

International The new national security adviser who will replace Robert C. McFarlane at the White House will be Vice Adm. John M. Poindexter, previously the deputy advisor. Admiral Poindexter was described by White House officials as smart, hard working and low-key. [Page A1, Column 1.] Bishops are in sharp disagreement over the form and substance of the final documents to be issued at the Synod in Rome. The pivotal question being debated is whether the Roman Catholic bishops should issue a statement of specific proposals to complement a pastoral message. [A1:3-4.] The French and Polish leaders met, generating protests in virtually all French political circles except the Communist Party. The 80-minute meeting between President Francois Mitterrand and Gen. Wojciech Jaruzelski, held at the general's request, was the first in a Western capital between the Polish leader and a Western head of state since Poland declared martial law in 1981. [A1:2.] A Polish priest was bound and beaten a second time this year, according to his mother, Teresa Zaleski. She said that the Rev. Tadeusz Zaleski, who was assaulted earlier this year because of his support for Solidarity, was attacked by three people who then ransacked his home. [A8:4.] Some U.S. anti-hijacking units may be deployed overseas. Administration officials said they were considering such action because of their failure to get specialists to the scene quickly enough to aid in last month's hijacking of an Egyptian airliner and in the takeover of the Achille Lauro cruise liner in October.