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Every fall, hundreds of students — sometimes as many as 800 — pack into Sanders Theatre for a course that promises to be “an experience,” unlike any other the College has to offer.

“This. Is. CS50,” David J. Malan ’99 announced as he began the first lecture of Harvard’s flagship computer science course CS50: An Introduction to Computer Science.

Malan, who took over the introductory computer science course in 2007, has opened each semester since with his signature line. It has become synonymous with his overhaul of the once daunting course — one that is now offered to over 5.8 million students on HarvardX, a free online learning platform.

While today’s students associate Malan — Harvard’s celebrity-like computer science professor — with the swag and fandom surrounding his trademark course CS50, he was first one of 457 students who enrolled in CS50 in the fall of 1996.

“As the saying goes, CS50 changed my life,” Malan wrote in a statement to The Crimson.

Entering college set on concentrating in Government with interests spanning history and constitutional law, Malan never believed he would find himself interested in computer science, let alone concentrating in it, until his sophomore fall — when he came across CS50.

“I finally got up the nerve my sophomore year to shop the course. And for the first time in 19 years (of life), I found that homework could actually be fun,” Malan wrote. “In fact, I used to look forward to going back to my room in Mather on Friday nights, around the time problem sets were released, to dive right in.”

Malan said that CS50 changed his perspective on Computer Science, which he had limited exposure to before attending Harvard.

“Contrary to what I’d seen in high school, where I saw friends of mine programming away in the computer lab, heads down sort of anti-socially, it really wasn’t that,” Malan said in an introductory CS50 lecture on Youtube. “It was much more about problem solving more generally and just learning how to express yourself in code, in different languages, so that you can actually solve problems of interest to you.”

Brian W. Kernighan, a professor of Computer Science at Princeton University who co-authored the first textbooks on the C programming language, taught Malan when he led CS50 as a visiting professor at Harvard.

“I never worked so hard in my life,” Kernighan said.

Malan still looks back on the “wonderful” teaching methods of Kernighan that have provided inspiration for the innovative approach he takes to teaching his version of CS50 today.

“I still remember him actually cutting his beard during class with, I think, a hedge clipper, to make the point that precision in algorithms is especially important,” wrote Malan, who is also known for his theatrics during lectures, most notably tearing a phonebook on stage to illustrate an efficient algorithm.

“He presented it in such an accessible way, a trait that hopefully characterizes CS50 today, along with its rigor,” he added.

Following Kernighan’s class — where Malan finished with the eighth highest grade — he felt it “was a sign” to pursue computer science. However, the pair never crossed paths during Malan’s time at the College — it would be over a decade until they would finally meet.

Kernighan has visited Malan’s CS50 course in Sanders Theatre on occasion and said he still learns more ideas and tricks each time.

“He’s just a dynamite presenter. Watching him on the stage is definitely a lot of fun,” he said. “If I was an inspiration in one direction, he’s an inspiration in the other.”

Now, Kernighan and Malan remain in regular correspondence, and are currently working on a project to compile and digitize the video recordings from the 1996 CS50 class which led Malan down his current trajectory.

“I could certainly count him as the high point of my academic success,” Kernighan said.

But to his classmates, Malan’s greatest contributions during his College years were his programming innovations, such as Shuttleboy — a computer program that displayed customized shuttle schedules for students.

Malan, a former Mather House resident, spent over 100 hours creating the computer program after one of his friends who lived in the Quad suggested the idea.

“I always thought it ironic that I, myself, never really took the shuttle,” he wrote.

Shuttleboy was an instant success on campus. The program was first shared through the Pforzheimer House email list, which Malan described as the most popular on campus, and it quickly spread through word of mouth.

“It rather took off from there,” Malan wrote. “At its peak, I think a few thousand undergrads were using it, and it was incredibly exciting to have built something that people were indeed using.”

At the time of its release Malan still insisted that programming was “just a hobby.” But the app outlasted his time as an undergraduate, evolving into new iterations including Shuttlegirl, ShuttleTime, and Shuttleboybot. Although no longer running the program, Malan maintained contact with the new creators and provided assistance in the development of the application Quad residents grew to love.

Before the creation of Shuttleboy — and only one semester after taking CS50 — Malan had already launched his first web-based application, designed to modernize registration for freshmen intramurals. Previously, those interested had to walk to a proctor’s room in Wigglesworth to register.

“I started to teach myself web programming (using a language called Perl) and implemented the program's first website via which classmates could register online,” Malan wrote.

Shortly afterwards, Malan and his roommate, Micol H. Christopher ’99, took over the intramurals program, with Malan running the website and Christopher, an athlete, leading the scheduling and games.

Beyond coding apps and a failed bid for president of the Undergraduate Council — Harvard’s former student government — Malan also excelled academically. As an undergraduate, he worked as a teaching fellow for an introductory computer science course at the Harvard Extension School. When the professor suddenly stepped down and asked Malan — a college senior at the time — to take over the course as its lead instructor, he said it was a simple case of “right time, right place.”

“I'm pretty sure I ended up being the youngest person in the room, teaching a class of 100 or so adults,” Malan wrote. “I even wore a suit with suspenders whilst teaching in hopes of looking older.”

“And that’s the experience that ultimately set me on my way,” he added.

—Staff writer Thomas J. Mete can be reached at thomas.mete@thecrimson.com. Follow him on Twitter @thomasjmete.