Continental Illinois Corp., which owns the troubled Continental Illinois National Bank, reported yesterday that its fourth-quarter earnings fell 43 percent from the fourth quarter of 1981 and that profits for the year plummeted 68 percent.

In other earnings reports yesterday, both BankAmerica Corp. and Santa Fe Industries Inc. said their profits fell in 1982, while Westinghouse Electric Corp. said earnings for both the fourth quarter and the year improved.

Continental was the major loser in the failure of Penn Square National Bank of Oklahoma last July. It bought $1 billion of energy loans originally made by Penn Square. Continental said yesterday that nearly $800 million of those loans have been written off or classified as a "nonperforming asset"--a loan that is not being paid back on time or on which the terms have been renegotiated.

But Chicago's biggest bank reported that its nonperforming assets, generally called problem loans, declined by $100 million during the final three months of 1982. Chairman Roger Anderson said that some problem loans were charged off as uncollectible but that many of the bank's problem real estate loans that were in arrears began repaying normally as lower interest rates stimulated the housing market.

Continental's main problem areas are domestic; it has a relatively smaller portion of its portfolio in foreign loans than such other major banks as Citicorp and Chase Manhattan. Continental is the nation's biggest lender to U.S. businesses.

Even with the decline in its problem loans, Continental, the nation's seventh largest, still has $1.9 billion in problem loans, by far the most of any bank in the country.

Continental's fourth-quarter profits before securities transactions were $41.3 million, down from $72.8 million in the final quarter of 1981. For the year, earnings were $84 million, compared with profits of $260.4 million in 1981.

About $600 million of the $1.9 billion of nonperforming assets were loans bought from Penn Square. Another $191 million of those loans have been written off as uncollectible. As a result of the Penn Square failure, about a dozen top Continental executives lost their jobs, including the man who had seemed to be Anderson's heir apparent, chief lending officer George R. Baker.

Anderson said that the bank added $105 million to its provision for potential loan losses in the fourth quarter and $492 million for the year as a whole. Additions to the loan loss provision come directly from earnings. In 1981, Continental deducted $120 million for its loan loss reserve.

Last year the bank had loan losses of $393.3 million, including the $191 million in bad Penn Square loans. In 1981 credit losses were $71.1 million.

BankAmerica Corp., hit by increased costs in its large consumer base and higher loan loss provisions, reported that earnings before securities transactions decreased 7 percent in 1982 and were down 19.3 percent in the final quarter of the year.

BankAmerica, holding company for the world's largest commercial bank, reported 1982 operating income of $419.6 million, or $2.81 a share, compared with income of $445.4 million ($3.02) in 1981. Final quarter income fell to $73.4 million (46 cents) from $84.6 million (57 cents) in the fourth quarter of 1981.

The corporation's net income increased slightly reflecting accounting changes and tax credits. In contrast to nonfinancial companies, operating income is the most significant indicator of a bank's earnings, since net earnings can be influenced by accounting and portfolio measures.

Santa Fe Industries Inc., citing reduced revenues from its railway operations, reported a net profit of $180.2 million ($2.08) for 1982, a decline of 26 percent from the previous year.

The company said that revenue from railway operations was the single most important factor in the decline. For both the fourth quarter and the year, Santa Fe said its railway car-loading operations were booking 17 percent less business than in 1981.

The company reported a fourth-quarter net profit of $26.2 million (32 cents), a 53 percent decline from the $55.2 million (62 cents) in the same quarter of 1981. It attributed part of the drop to expanded railway maintenance programs.

Westinghouse Electric Corp. said earnings rose 3 percent from $438 million ($5.10) in 1981 to $449.3 million ($5.16) in 1982, while sales increased 4 percent from $9.37 billion in 1981 to $9.75 billion last year.

For the fourth quarter of 1982, Westinghouse said it earned $100.8 million ($1.13) on sales of $2.61 billion. For the same period of 1981, the company said it earned $103.1 million ($1.20) on sales of $2.53 billion.

"Given the economic conditions in 1982, Westinghouse had a good year with increased sales and earnings," said Chairman Robert E. Kirby. "Even though the near-term economic outlook remains uncertain, we see some signs that indicate the recession is bottoming out."

Westinghouse said its power systems and public systems units showed significantly higher profits in the fourth quarter, while broadcasting and cable units were about even and industry products were sharply lower.