HARLOTTESVILLE, Va., May 9 ù As they have for 160 years, students at the University of Virginia took their final exams unsupervised today, despite a cheating scandal that has shaken the campus.

Under trees and on benches, on a beautiful spring day, lone figures scrawled their answers in blue books, with teachers trusting that students would not peek into textbooks, steal solutions from the Internet or seek help from friends.

But the University of Virginia's code of student honor, a proud tradition that relies on students signing pledges not to cheat, steal or lie, is facing what may be its most severe test. Some 122 students stand accused of cheating on term papers in a popular introductory physics class, with as many as half of them expected to face the only penalty available for cheating here: expulsion or loss of degrees awarded in earlier years.

The scandal at this campus of 18,000 as the academic year ends has prompted new questions about the university's widely admired code of honor and its single sanction system, rare among American universities.

Cheating was discovered after a student from last semester told Louis A. Bloomfield, the physics professor, that the grade he had given her paper was low and that others with higher marks had cheated. The class has 300 to 500 students each semester.

Professor Bloomfield set up a computer program to detect similarities of six consecutive words or more between term papers submitted to him over the last five semesters. It took the program 50 hours to run through more than 1,800 papers, but it was not long before the first matches appeared, he said, and they showed the papers to be virtual replicas.

"In this universe, it's not 6 or 12 identical words in a phrase," Professor Bloomfield said, "it's 1,500."

"I expected to see a couple of matches," he said. "I was a bit shocked to find 60."

Professor Bloomfield's discovery was first reported in The Richmond Times-Dispatch.

He suggested that in an era when people swap music over the Internet, forward e-mail messages and send texts to each other with a single keystroke, the lines between collaboration and theft have blurred.

While some educators have raised concerns that the Internet has made cheating on exams and term papers easier, Professor Bloomfield's program raises the potential of electronic sleuthing to match it.

Some university officials say they suspect the Internet has increased cheating. But Linda K. Trevino, chairman of the department of management and organization at Pennsylvania State University's business school, said she found little evidence that cheating on term papers had increased when she compared a 1963 survey of students with one she wrote in 1993 with Donald McCabe, a Rutgers University professor who founded the Center for Academic Integrity.

But Dr. McCabe said he believed that cheating on exams had increased sharply. In the 1960's, he said, one in four students admitted to cheating once or more on a test in the previous year. By 1993, that figure had doubled.

Both researchers said that colleges that relied on an honor code appeared to have less cheating.

In 1993, 53 percent of students at schools without honor systems admitted to cheating once or more on a test in the previous year, while 29 percent of students at schools with honor codes admitted cheating. Two out of three students surveyed at colleges and universities without an honor code admitted to copying another student's papers, while 42 percent of students on honor codes said they had done so.

Thomas Hall, a student who heads the University of Virginia's Honor Committee, said that an investigative panel was going through the 122 cases Professor Bloomfield had referred, and that some students were found to have cheated and been told they would be expelled. Often, he said, the students whose papers were copied said they had shared their work to help a fellow student, but did not know it would be plagiarized. In those cases, the students have not been thrown out.

Several students under investigation had graduated, Mr. Hall said, and so could see their degrees revoked.

"The majority of students who don't cheat don't want to put up with those that do," said David Gies, a Spanish professor and former head of the faculty senate.

Professor Gies said that he welcomed Professor Bloomfield's discovery of cheating, and that the expulsions would force students to think twice about cheating.

At the Alderman Library, undergraduates facing final exams said the plagiarists should be punished, but some raised questions about the fairness of scrutinizing just one class.

"I would agree to it if they could apply it to everyone," Chris Reams, a sophomore from Richmond, said.

He said he knew of students who cheated in advanced economics courses that were essential for admission to business school, driving up the grading curve. Though he considers them more serious offenders, he never reported them.

"The honor system is like a death penalty," Mr. Reams said. "Because it's so severe, if you see cheating, and I have, you're reluctant to report it, so we end up resorting to these spy systems. We've created an atmosphere that makes cheating more seductive."

Sean Turner and Jason Bakelar studied for a calculus test just hours away.

"I'm having a hard time finding a gray area when you say, What's cheating and what's not?" Mr. Bakelar, a senior majoring in politics, said.

Mr. Turner, a junior majoring in economics, agreed, saying students caught cheating should be expelled. "It's not fair to students like us," he said, "who study and do our work."

But Kristen Edington, a freshman about to take a final in a class on religion and ethics said, "I think the honor system's an ideal." By giving students so much freedom, she said, "it sets up for people to cheat and steal and lie."