What was going on when I was born?

Secretary of Defense Caspar W. Weinberger informed Congress today that the Reagan Administration planned to ask for a 1983 military budget of nearly $260 billion in appropriations, or $10 billion more than previously expected, according to Administration and Congressional officials. Mr. Weinberger, in a closed session with the Senate Armed Services Committee, also said that the Administration p lanned that actual military spen ding for the fiscal year starting in October would total$216 billion, which was expected. The officials, who declined to be identifie d because the session was held in President Reagan is ''lukewarm'' to his own withholding tax plan, according to Treasury Secretary Donald T. Regan. Page D1. secret, said the increase in military appropriations to be requested next week had come from more realistic assessment of the rate of inflation.

THERE seems to be no limit to the number of ways and places in which Americans take their meals: in bed, at coffee-shop counters, while sandwiched between other passengers on commuter trains, from brown bags at their desk. They eat chili to the twang of country and Western music and hamburgers that are served by waitresses on roller skates. They dine at drive-ins where plastic trays are fixed to their car windows and in restaurants where the lights are so dim that flashlights are needed to read the menu. At home, meals often turn into a sort of relay race, the freezer's treasures being consumed in front of the television set by one family member at a time. Considering that diversity of setting, one might ask, just how much does ambiance affect th e enjoyment of food? D oes the atmosphere of anelegant restaurant enhance the pleasure of wh at is eaten there? Does it really matter if we are watching the news, reading a book, having an argument or listening to classical music w hile we dine?

The Internal Revenue Service takes an expansive view of income, and requires that just about everything from bartered goods, salary and wages to lottery prizes and even kickbacks be reported on a tax return. But new provisions in the law double the amount of di vidend income that i nvestors can exclude on their 1981 returns, and allow people to she lter their interest income in two new ways. The general rule is that taxpayers must include all payments for services rendered, including such items as severance pay, union strike benefits and under-the-t able commissio ns. Gambling victories must be reported (losses can be deducted as a n itemized deduction, but only up to the amount of winnings), and s o must illegal income such as embezzled funds. Alimony and separate maintenance payments are considered income, but child support paym ents are not. Taxpayers must also list a certain portion of their income from investments, such as stock dividends or interest on bank savings accounts. The amount and type of investment income that can be excluded this year has been liberalized as a result of the 1980 Windfall Profit Tax Act.

An article in Metropolitan Report on Thursday about the reassignment of judges to Criminal Court incorrectly described the status of Judge Irving Lang. He is serving temporarily in Criminal Court and will be eligible to return to the Supreme Court as an act- ing justice on Jan. 1, 1985.

"I am not about to lay out a litany of actions that may or may not take place.

More than 200 lawyers and others in the Justice Department's civil rights division have signed a letter expressing ''serious concerns'' about the Reagan Administration's decision that racially discriminatory private schools are entitled to tax exemptions under current law, Justice Department sources said today. The letter represents a continuation of a long and intense debate in the Administration that led up to the decision Jan. 8 to grant tax exemptions to segregationist schools. Some of the high-level in- Text of letter, page A21. ternal conflicts before that decision have just become known through Justice and Treasury Department documents obtained by the Senate Finance Committee, which is holding hearings on Mr. Reagan's proposal for a law to deny the exemptions.

The standardized ability tests widely used to screen applicants for schools and jobs are generally valid and not in themselves unfair to blacks and other minority people, a panel formed by the National Academy of Sciences concluded today after four years of study. The special panel warned, however, that the tests had ''inherent limitations'' and could have an adverse ''social impact'' on certain groups if relied upon too heavily in admissions and hiring decisions. ''Research evidence does not support the notion that tests systematically underpredict the performance of minority group members,'' the panel's spokesman, Lyle V. Jones of the University of North Carolina, said in a statement. But he said that when selection processes were dominated by test scores, which show large differences in average scores between blacks and whites, they do tend to screen out black applicants.

The American Telephone and Telegraph Company reported yesterday that its net income for the year rose 13.7 percent, to $6.89 billion, or $8.55 a share, the highest profit ever reported by any company in the world. The increase, almost twice the 7.2 percent improvement that the phone company registered in 1980, came to a large extent as a result of higher phone rates. The 1981 profits compare with $6.06 billion, or $8.17 a share, earned in 1980. These numbers were restated slightly to reflect an accounting change.

When the RCA Corporation put its Hertz subsidiary up for sale last week investment bankers speculated that the prospective buyer would have to be of one extreme or another: either very reckless or very sophisticated. Very reckless, they ventured, because all the leading auto rental companies have been in an earnings slump for at least the last three months, due to a rather unlikely confluence of high interest rates, increased car prices, a recession, reduced air travel from the controllers' strike, a strong dollar in Europe and a price war. Or very sophisticated, they countered, because once the current business cycle is over, the profit and tax-sheltering potential of a longtime industry leader like Hertz will be almost limitless - especially for the right parent with the right-size pocketbook. Bennett E. Bidwell, Hertz's 54-year-old president, would like to think that whoever buys his company will be of the latter persuasion. ''With the right parent,'' he muses, ''there are a lot of places we can go.''

The State Commerce Commissioner has urged Governor Carey to call for substantial cuts in the state's personal income-tax rate and will make his position public in a speech on Wednesday. Mr. Carey included no such tax reductions in his budget proposal to the Legislature last month. But when the Commissioner, George Dempster, was asked about reports of his forthcoming speech, he said, ''I wouldn't advance a policy consideration of this magnitude without having reviewed it with the Governor and received the encouragement to explore the idea.''

New factory orders increased by a scant two-tenths of 1 percent in December, the Government reported today. However, the increase was seen as encouraging in light of separate reports that showed sales of newly built houses in December rose 10.9 percent, the third straight monthly gain, and that the value of new construction in December was up 21 percent from November, the low point of 1981. (Page D12.)

Secretary of State Alexander M. Haig Jr. declared today that the United States, in cooperation with its allies in Latin America, would do ''whatever is necessary'' to prevent the overthrow of the Salvadoran Government by guerrillas he said were backed by Cuba and Nicaragua. Under questioning by the Senate Foreign Relations Committee, Mr. Haig again refused to say whether the Admin- Excerpts from testimony, page A8. istration was contemplating sending combat troops to El Salvador. Ever since the Reagan Administration became concerned about the situation in El Salvador a year ago, Secretary Haig has left open the possibility of some form of American military action in the region. Officials have said this was deliberate and intended to keep the Soviet Union, Cuba and Nicaragua off balance.