As a result of such changes, students on some campuses said they felt shut out of computer science while others said they faced overcrowded classes with overworked professors.

Aafia Ahmad, a sophomore computer science major at U.T. Austin, had hoped to take an elective course in computer security this semester. But when she tried to sign up during early registration in November, the course was already full. She said that was the case for nearly every computer science elective she wanted. She is now 79th on a waiting list for the security course.

“It’s a cutthroat race to register for classes,” she said.

Some university leaders said they were concerned that certain measures taken to address surging student demand may disadvantage people who are already unrepresented in computer science — including women, African-Americans, Latinos and low-income, first-generation college students.

Some universities now require incoming students to get accepted into computer science majors before they arrive on campus — and make it nearly impossible for other undergraduates to transfer into the major. That approach can favor incoming students from schools with resources like advanced programming courses. It can also favor male students — because women on average are less likely to have taken a computer science course in high school.

“When you put any kind of barrier in place in terms of access to computer science majors, it tends to reduce the number of women and students of color in the program,” said Maria Klawe, president of Harvey Mudd College, a private college in Claremont, Calif., that has become a national model for diversity in computer science.