It is very perplexing for foreigners to understand how Americans change presidents. I happened to be with a military attache from a South American country this weekend who is going to cover his first inaugural.

He was quite bewildered about how it was to be done.

"What will President Carter be doing up there on the platform?" he wanted to know.

"He'll be watching the new president of the United States being sworn in."

"Isn't Carter under house arrest?"

"No, we don't put our presidents under house arrest," I told him. "It's much more cruel to make them see their successor take over the office."

"Will there by any colonels up on the platform?"

"Why should there be colonels on the platform?"

"We always give the colonels who overthrow our government the best seats."

"Our colonels didn't overthrow the government. The president was elected by the people."

"But didn't you have the junta oversee the elections?"

"We had no junta. People just went to the polls and voted for the candidate they wanted."

"How can you do that under martial law?"

"We didn't have martial law," I said, patiently.

"But if Carter knew that Reagan was going to overthrow his government, why didn't he declare martial law and round up all the people who were supporting Reagan?"

"Our system is not that sophisticated yet. Every president takes his chances that he can win re-election. Once the voters have spoken, that's it."

"It doesn't make any sense that a man in power would not have any knowledge that the opposition was planning a coup. What happened to the generals who were supporting Carter?"

"Carter didn't have any generals supporting him in office."

"That explains it! But surely the secret police could have tortured the Reagan people and found out what was going on."

"We're way behind when it comes to torturing political opponents. We just let everyone have his say and then we select the person we want to be our president for four years."

"You mean Reagan is not going to declare himself president for life?"

"He can't. The constitution won't permit it."

"But surely he can change the Constitution. We do it all the time."

"It's too much trouble," I said. "Besides, being president of the United States for four years can seem like a lifetime."

"When do the trials of Carter's Cabinet officers begin?"

"There are not going to be any trials. Most of them will go back to their law practices or head up large corporations."

"How can Reagan be sure they won't work clandestinely to overthrow him?"

"They will, but not until 1984."

"Will there be any tanks up here?"

"We never have tanks at a presidential inauguration. They make potholes in the streets. Pay attention on Tuesday and you could learn something from this."

"What good would it do? When I make a report to my government, no one in the junta will believe me."