Just before 9 a.m., Jimmy Carter's motorcade pulled up in front of the First Baptist Church at 16th and O Streets NW. There, Carter and his family joined Vice Presient-elect Walter F. Mondale and his family, members of the Cabinet and others to pray together in the last hours before the beginning of a new administration.

Seven hours later, after all the ceremony and hoopla, the new President, clutching the hand of his wife, Rosalynn, walked across the snow-covered White House lawn to the north portico of the executive mansion.

"It's been just about a perfect day, a satisfying day," Carter said at the entrance to the White House. "It's been very exhilarating, and a reminder of what our country is and the trust that people have in me, and I have a strong determination not to disappoint them."

Less than an hour after that, while members of his family were touring the White House, Carter entered the Oval Office, where his desk contained a single sheet of paper listing his first official visitors.

Appropriately and symbolically enough, the first name on the list was that of Hamilton Jordan, the 32-year-old chief architect of his presidential campaign.

The others, whom Carter described as "job applicants," were Charles Warren, a state legislator from California; Max Cleland, a former Georgia state senator, and Sam Brown, an anti-Vietnam war activist who is now Colorado state tresurer.

Cleland, a paraplegic since he suffered wounds in Vietnam, is a leading candidate to be named administrator of the Veterans Administration. It is not known what jobs the others are being considered for in the administration.

Carter's first official acts as President occurred shortly after the inaugural ceremonies in Room S-208 of the Capitol. Carter signed a document officially nominating all of his Cabinet designees for their positions and separate documents officially nominating Andrew M. Young to be U.S. Ambassador to the United Nations, Thomas B. (Bert) Lance to be director of the Office of Management and Budget and Charles L. Schuitz to be chairman of the Council of Economic Advisers.

He was asked how it felt to be President of the United States.

"It feels very gratifying, very sobering, I'd say, to some degree, humbling," he replied. "I want to be sure that I do a good job. When the bishop said 'President Carter' for the first time, it kind of shocked me a little bit."

Throughout the cold of the day, the President was accompanied by his wife and their 9-year-old daughter, Amy.

After a breakfast of scrambled eggs with his family and a 15-minute intelligence briefing that he has been receiving each day since he was elected, Carter left Blair House shortly before 9 a.m. for the brief trip to the First Baptist Church and the beginning of a momentous day.

Reporters were barred from the service, but later the pastor, the Rev. Charles A. Trentham, said he had told Carter and the congregation: "You are now in a church that has pledged to pray daily for you. I believe in Jimmy Carter. I voted for him. On the day he was nominated, I thanked God for the emergence of a new leader. . ."

After a brief return to Blair House following the service, Carter and his wife emerged once again into the cold and sunlight, this time to walk hand in hand up Pennsylvania Avenue to the White House and a final meeting with President and Mrs. Ford.

Walking up the White House driveway, Carter turned to House Speaker Thomas P. (Tip) O'Neill and said, "Isn't the weather beautiful?" He added, with a broad grin, "I appreciate the Congress being so good to me."

The Fords and Vice President and Mrs. Rockefeller greeted the Carters at the north portico. The incoming and outgoing Presidents and their wives spent 15 minutes together talking and sipping coffee in the White House Blue Room.

From there, tradition and ritual took over - the slow ride up Pennsylvania Avenue to the Capitol, Carter and Ford together in the presidential limousine; the hymms and prayers on the Capitol steps; the administering of the oath of office; the inaugural address.

It was only when all this was over that tradition was broken in the first symbolic act of a new President. Shortly after the limousine left the Capitol grounds for the parade, the President left the car to walk the mile and half to the White House. It was a singal of the end of "the imperial presidency," an aide said.

And when he was finally in the White House, at about 4:30 p.m. yesterday, Jimmy Carter sat down at the desk in the Oval Office. The room had been stripped of pictures and other memories of the Ford presidency. Once again, Carter was asked how it felt to be President of the United States, to hold the office so many have sought but so few have gained.

"It feels good so far," he said.