A class of Introduction to Programming students was on its best behavior Wednesday after Microsoft founder Bill Gates unexpectedly stepped in as substitute teacher for the day.

As part of the broadband cable network mtvU's "Stand In" series, in which celebrities drop in to college classrooms unannounced and teach for a day, Gates spoke to Computer Science 302 students about the importance and versatility of pursuing a career in computer programming.

Gates' stop at the University of Wisconsin was also part of a week-long tour of six universities promoting information technology and engineering careers.

Despite numerous video cameras and unidentified "guests" — including an undercover police officer with a bomb-sniffing dog in tow — all under the facade of an "educational video shoot," the unsuspecting students were star struck after a knock at the door revealed the Microsoft Corporation chairman and chief software architect as their teacher for the remainder of the period.

"This is my first visit to the university. I thought I'd drop by," Gates said shortly after students realized he was actually in their classroom. "I want to talk a little bit about software and what's going on, some of the opportunities there, and then I'll have a chance to answer any questions you have, so, hopefully, you'll think up some good questions."

Gates enumerated the importance of software and how critical programmers are to the advancement of all scientific fields.

"If we think about all the areas of science, software is coming in to be the thing that makes the biggest difference," he said. "In biology, they're [dealing] with lots of data about genes and proteins and who got sick, very complex data. What is the tool that will let them make sense of that? Software."

Attempting to dispel common myths surrounding computer jobs, Gates spoke of the exciting opportunities available in computer science.

"I do think that a lot of people who have an image of the profession as not being that fun … miss the opportunity to come in and do it," he said. "We've got really among the most interesting jobs in the whole field."

Gates added that it is important for the United States to remain at the forefront of the industry. He encouraged students venturing into the field to uphold its preeminence by pursuing computer science degrees.

"It is an issue for the country that we want this country to continue to be by far the best in computer science," he said. "And that's why this country has done so well … because universities like this one and dozens of others have great programs and lots of people who go into [them]."

Gates' message moved the students. He boosted their confidence and told them computer science is not for nerds.

After Gates' visit, UW junior Colin Hall said he was "inspired" by his message and attention to the future of the field.

"Well, I had no idea that he was coming. … I didn't even recognize him as he was coming in," he said. "It really reinforced my belief that computer science really is a good thing to get into, and to hear it from the guy who really made it big with computers is just overwhelming."

Meanwhile, teaching assistant Aneesh Karve clearly didn't mind Gates interrupting his class.

"I'm really happy for my class that they got to meet such an influential figure of our time," he said. "I'm totally blown away and feel totally lucky that by whatever random chance, our class got chosen to be visited."

Later during his visit, Gates spoke to an exclusive group of computer science, engineering and other science students in Weeks Hall about the future of computer technology and managed to show off some of his latest innovations, including the new Xbox.

In a later interview, Gates admitted he did see a "tiny bit" of irony in encouraging students to get a computer sciences degree after dropping out of Harvard himself. "Believe me, if they know as much about computer science as I did when I dropped out, that's OK, too," he said. "I was a computer nut."