Hotel Genius

D is for dedicated teacher

Kernighan trades front lines of tech revolution for front of the classroom

By Steven Schultz

Princeton NJ – Just a few hours after Opening Exercises on Sept. 7, members of the class of 2007 gathered in Richardson Auditorium for the first academic experience of their Princeton careers.

A slender man with glasses and a fluffy white beard took to the stage, cell phone and pen in the pocket of his open-collared blue shirt. Bypassing the podium, Princeton computer scientist Brian Kernighan perched himself on a metal stool and began his talk, “D Is for Digital and Why It Matters.”

Computer scientist Brian Kernighan has earned a reputation among students as a gifted explainer and dedicated mentor. Here, Kernighan and his senior thesis advisee Thaís Melo select bits of old computer hardware for him to bring to his introductory course, “Computers in Our World.”

If anyone understands the subject, it is Kernighan. He spent 30 years at the front lines of a technological revolution and has created widely used computer software. Since coming to Princeton from Bell Labs in 1999, however, Kernighan has built on his reputation as a computing pioneer and is earning praise as a master teacher.

For 40 minutes, Kernighan played music, cracked jokes and gently walked 1,000 freshmen through the convergence of history and science that is remaking their world. He cast Mozart as one of the first music pirates and explained how digital technology has created unprecedented social, economic and political opportunities and challenges.

“I don’t think I need to say too much to make the point that we are surrounded by gadgets – cell phones, digital cameras, computers and DVDs,” said Kernighan, who believes these devices will affect our lives whether we like it or not, whether we understand them or not. “Perhaps we ought to know something about them and maybe, in some way, be comfortable with them so we can prepare for what they may bring us in the future.”

It’s a theme that Kernighan has taken up with extraordinary success in his course “Computers in Our World,” which seeks to build technical literacy among nonscientists and continues to receive glowing reviews years after students take it.

“We are so lucky to have him,” said senior Jackie Cheung, who took the course as a freshman. “He just combines that real interest in what students do, an amazing intellectual capacity and real talent for teaching.”

“He is exactly the kind of undergraduate professor you’d want,” summed up Joseph Falencki, who is a senior politics major and took Kernighan’s course last year.

For longtime colleagues, Kernighan’s strength as a teacher is not necessarily a surprise. “If you look back to his work at Bell Labs, you really see two kinds of contributions,” said Dean of the Faculty David Dobkin, who, as chair of the computer science department, was instrumental in bringing Kernighan to Princeton. “On the one hand, he’s a great scientist; many scientific discoveries have his name written all over them. On the other hand, he is a great expositor. There are very few people in computer science whose writing is as well known as his.”

At Bell Labs, Kernighan was part of the research group that created the powerful and widely used Unix operating system. In addition to making technical contributions, Kernighan was the one who proposed the name Unix. The programming language “C” was created in the same group by Dennis Ritchie. Kernighan teamed up with Ritchie to write a book explaining how to use the language. Their book, translated into more than 20 languages, became so widely read that it is now referred to simply as “K&R” and that version of C is often called “K&R C.”

Kernighan is the author or co-author of several other top-selling technical texts, including one he revised last summer on another programming language called AMPL. “In some cases, his writing really made the subject,” said Dobkin.

‘An enormous blast’

Kernighan, who went straight to Bell Labs after receiving his Ph.D. from Princeton in 1969, returned to a university classroom in 1993. Dobkin was taking a sabbatical and invited Kernighan to fill in teaching a junior-level advanced programming course. (“When people found out he was going to teach it, enrollment in the class shot up,” Dobkin said. Kernighan has now taken over that course.)

In 1996, he played substitute again, this time at Harvard, for a large introductory class that had an unwieldy combination of students, ranging from first-year computer science majors to senior humanities majors. In addition to realizing he could handle 450 students and 31 teaching assistants, Kernighan began to sense the thrill of being in front of a class and connecting with his audience. “That was the hardest I ever worked in my whole life,” Kernighan said. “But it was an enormous blast.”

The Harvard course also attracted Kernighan to the idea of teaching nonscientists. When Dobkin invited him as a 250th Anniversary Visiting Professor for Distinguished Teaching in 1999, Kernighan jumped at the chance and created “Computers in Our World.” The following year, he retired from Bell Labs and joined the Princeton faculty, where he now devotes the majority of his time to teaching, although he continues to pursue several research projects.

For his students, Kernighan’s shift in attention could hardly seem more natural. He has an uncanny ability to recall names, even in the first sessions of a large lecture course and often surprises former students by recalling their specific interests years later. “After I say something to him just in passing, he’ll send me a really long e-mail giving me ideas and feedback and send me books, even if it’s completely not related to computer science,” said Cheung.

From Mozart to Dion

For Kernighan, his introductory course allows him to pursue one of his heartfelt missions: giving nonscience students the confidence to make their own evaluations of technical issues. In one assignment, he asks students to puzzle out how their prox cards work to unlock dormitory doors; in another, they evaluate the “facts” under the lids of Snapple drink bottles.

Falencki said the course helped him when he worked for an insurance company last fall and someone from the information technology department came to talk about the rash of computer viruses. “I could actually understand what [the virus] was doing,” he said. “The other people in my department had no idea what the guy was talking about. I had become computer literate to some degree.”

Teaching also has allowed Kernighan to indulge his eclectic intellectual interests as he peppers his lectures with references to current events, popular culture and the arts. In addition to keeping up with the latest music-swapping technology, he plows through two or three books a week and is a habitual visitor to a local used CD store.

In his freshman orientation lecture, Kernighan focused on a subject close to students' hearts – digital music sharing – but connected it to a story about 17th-century composer Gregorio Allegri. Kernighan played a haunting passage from Allegri’s “Miserere,” which was written in 1638. By order of the pope, it could only be sung in the Sistine Chapel during Easter week. One hundred and forty years later, the 14-year-old Mozart heard the piece and wrote the score from memory. Suddenly the restriction was broken and the piece became widely available.

Later in the lecture, Kernighan pulled out a CD by the pop star Céline Dion and showed how technology designed to stop it from being copied could be circumvented with a felt-tip pen.

The audience erupted in cheers and laughter, but Kernighan quickly took the discussion in another direction. New laws designed to curb digital piracy could have the absurd effect of making it illegal to hand someone else the pen because that would be trafficking in a technology for circumventing copyrights. If Congress and the rest of America are to come up with reasonable solutions, a solid understanding of the technology is critical, he said.

“The physical devices that make all this possible continue to get smaller, cheaper, faster, better, at an exponential rate,” Kernighan said. “That means rapid change and, almost guaranteed, disruptive change. And that is going to happen as far into the future as we can see.”

Leaving the freshmen with that thought and proposing some questions they might discuss in precept groups after the lecture, Kernighan quoted Francis Bacon. “He said, ‘A prudent question is one-half of wisdom.’ So your job, starting tonight, for the next four years, for the rest of your lives: Ask the prudent questions.”

Brian Kernighan’s address, “D Is for Digital and Why It Matters” is available online at