Bill Gates (Microsoft)

Age: 19
In 1975, Bill Gates famously dropped out of Harvard (where he lived down the hall from fellow sophomore, Steve Ballmer) to start a company with childhood friend Paul Allen, who had recently dropped out of Washington State University, in order to work at Honeywell in Boston. Gates had already been programming for a number of years before co-founding the company first known as Micro-Soft (a combination of “microcomputer” and “software”).
He encountered his first computer at age 13, at Lakeside School in Seattle. He soon received a pass from math class, so he could work on the ASR-33 during school hours, creating his first computer program—a version of tic-tac-toe written in BASIC.

Mark Zuckerberg (Facebook)

Age: 19
Fellow Harvard alum turned billionaire Mark Zuckerberg also thought up the idea that earned him his fortune at the ripe old age of 19. It was Zuckerberg’s father who first planted the programming bug in the middle school student, teaching him how to program in Atari BASIC.
By the time he was in high school, Zuck was taking grad courses in the subject at a local college, soon creating ZuckNet, a personal instant messaging program he used to communicate with his father. Soon after, he developed Synapse Media Player, an AI music player that we gave three out of five stars, back in 2005. It’s no Facebook, but still, not too shabby for a high school kid.

Michael Dell (Dell Computers)

Age: 19
There are those who put off the working world for as long as possible, enrolling in graduate school well into their 30s. And then there’s Michael Dell, founder of his eponymous computer company, who applied to take a high school equivalency exam at age eight, in order to enter the business world as soon as humanly possible.
By age 15, after having disassembled his share of Radio Shack calculators, Dell got his hands on an Apple II, which he promptly took apart. At 19, while enrolled at University of Texas at Austin as a pre-med student, Dell launched PC’s Limited, banking on the concept of selling computers directly to consumers. Eight years later, he was the youngest CEO to make the Fortune 500 list.

Steve Jobs (Apple)

Age: 21
Steve Jobs got a summer job working at Hewlett-Packard while still in high school. It was there that he met future “Dancing with the Stars” participant, Steve Wozniak. In 1975, the two Steves were briefly employed by Atari—that same year, they began attending the Homebrew Computer Club, a small grew of hobbyists that would later become the epicenter of the personal computer revolution. It was in front of that group that Wozniak and Jobs first showed off the Apple I, a fully assembled circuit board hand-built by the Woz. The young company charged an ominous $666.66 for that first computer.

Larry Page, Sergey Brin (Google)

Age: 25
Faced with anti-Semitism in the academic environment of their native Russia, the Brin family moved to the U.S. with their six-year-old son Sergey in 1979. Partially homeschooled by his father, then a math professor at the University of Maryland, Brin eventually enrolled at his father’s school, where he graduated with honors.
Soon after, he began graduate work in computer science at Stanford, where he met Larry Page. After butting heads for some time, the two eventually became “intellectual soulmates,” according to Brin. Together Page and Brin went on to create “BackRub,” a new search engine named for its reliance of checking backlinks. Thankfully, they soon opted for the less creepy Google, named for googol, a number followed by 100 zeros.

William Hewlett, David Packard (Hewlett-Packard)

Age: 26 (Hewlett), 27 (Packard)
Like a number of fellow future technology giants, Hewlett-Packard was born in a Bay Area garage. The space belonged to Frederick Terman, William Hewlett and David Packard’s former professor at Stanford. It was there that the duo launched the company with an investment of $538, choosing the order of their hyphenated company name with the toss of a coin.

Fusajiro Yamauchi (Nintendo)

Age: 30
In 1889, Fusajiro Yamauchi started a new game company specializing in Hanafuda playing cards made from mulberry tree bark. The name “Nintendo,” in keeping with the theme of that early product, means “leave luck to heaven.” The company specialized in cards for nearly a hundred years after.