For the second year running, Computer Science 50: “Introduction to Computer Science I,” has edged out Economics 10a: “Principles of Economics” for the title of the semester’s largest undergraduate course at Harvard.

As of Tuesday afternoon, CS50 touted a roster of 703 undergraduates, while Ec 10 had enrolled 700, according to course enrollment data compiled by the Faculty of Arts and Sciences Registrar. {shortcode-419aa0b06038213e33840f2a3e897110b9703a12}

The Registrar’s office posted these course enrollment numbers online after add/drop period—when students can enroll in or withdraw from courses without a fee—ended Monday at midnight, according to FAS Registrar Michael P. Burke. Course enrollment numbers will continue to be updated daily, Burke wrote in an email.

The two largest undergraduate courses, Harvard’s flagship classes in Computer Science and Economics, have consistently drawn hundreds of College students over the past few semesters. Ec 10 has maintained its standing as one of the College’s largest courses in both the fall and spring terms. And last fall, CS50 logged a record-breaking total of undergraduate enrollees.

Having expanded to New Haven this semester, CS50 now can add “Yale’s most popular course” to its bevy of titles. There are 510 students enrolled in the Yale version of the course—called Computer Science 100: “Introduction to Computing and Programming”—represening about 10 percent of Yale undergraduates, according to The Yale Daily News.

Students flock to CS50 in part because many industries have growing interests in computer science, according to David J. Malan ’99, a Computer Science professor of the practice who teaches the course. Malan also hopes CS50 attracts “students more and less comfortable alike...irrespective of prior background,” he wrote in an email.

“I'd also hope it's a reflection of the course's accessibility, culture, and rigor,” Malan wrote, discussing his thoughts about the course’s consistently high enrollment.

Economics professor N. Gregory Mankiw, who teaches Ec 10, also said his course’s practical implications prompt a large number of undergraduates to take the course. Students are attracted to economics because they want to be “well-informed” citizens, Mankiw wrote in an email.

“I keep wondering: Why isn’t every Harvard first-year student taking [E]c 10?” Mankiw wrote.

For both course instructors, however, large class sizes have pros and cons.

“The main advantage is that it provides a common focal experience for Harvard students,” Mankiw wrote about Ec 10. “The main disadvantage is that I don’t get to know all the students individually.”

Malan echoed Mankiw, writing that teaching large numbers of students places new demands on course staff.

“We've certainly had to build out the course's support structure all the more,” Malan wrote. “Wonderfully, though, the more students who take the course, the more candidates we have for future TFs and CAs!”

—Staff writer Melissa C. Rodman can be reached at melissa.rodman@thecrimson.com. Follow her on Twitter @melissa_rodman.