What were you doing during your 20s?
Probably attending a college or university, enjoying your youth, and having new experiences away from home.
Many of technology’s most notable billionaires were doing no such thing.
Michael Dell for instance was already investing in stocks and precious metals before he graduated high school.
During their early years, Dell and the other seven entrepreneurs were busy laying the foundations of some for today’s biggest and most recognisable companies.
Zuckerberg, a Harvard drop out, was already a billionaire from Facebook at the age of 23.
By the time Zuck was 25, Facebook had an estimated 500 million users worldwide. Also during this time Zuckerberg was involved in various legal disputes initiated by others who claimed a share of the company because they helped to set it up.
When Zuckerberg was 26, he was honored as TIME Magazine's person of the year.
In his early 20s Bill Gates dropped out of Harvard and decided to start his own software company with friend and co-founder of Microsoft Paul Allen.
Microsoft's official history says that in 1975, when Gates was just 20 years old he and friend Paul Allen were inspired by the MITS Altair 8800 a computer system. Gates and Allen began to develop a BASIC language for the Altair.
One month later, Gates and Allen sell BASIC, the first computer language program for a personal computer, to Microsoft's first customer, MITS of Albuquerque, NM.
Steve Jobs trekked to India during his 20s and had a life-altering experience, shortly after he returned from his trip he became a Buddhist.
At the age of 19, Steve Jobs took a job as a technician at legendary game company Atari.
By the time he was 20 he had a reputation for 'being the smartest guy in the room' and but also difficult to work with.
At the age of 21, Jobs and long-time friend Steve Wozniak formed their own company, selling circuit boards. They named 'Apple Computer Company' remembering a happy summer Jobs had spent picking apples.
During his 20s Steve Ballmer was attending Harvard University where he majored in maths and economics.
At Harvard Ballmer stayed down the hall from Microsoft founder Bill Gates. After graduating college Baller worked a two-year stint as an assistant product manager at consumer goods company, Proctor & Gamble.
At age 24, Ballmer dropped out of Business School at Stanford to became Microsoft's 30th employee. Ballmer was the company's first business manager hired directly by Bill Gates.
It was during their early 20s that Google co-founders Larry Page and Sergey Brin met. The two were both Ph.D candidates at Stanford University.
Brin said the two, 'seemed to disagree on most subjects'. But after spending time together, they 'became intellectual soul-mates and close friends'.
Brin and Page later developed the 'PageRank algorithm', and realised that it could be used to build a search engine much better than those that already existed.
By the time they were 25 they started Google, today's largest search engine.
Before the age of 20, Michael Dell was already investing his money from part-time jobs in stocks and precious metals.
After graduating High School, Dell enrolled as a pre-med student at the University of Texas at Austin. During this time he started a informal business selling upgrade kits for PCs out of his dorm.
At the age of 19, Dell dropped out of college and established his computer business, which sold between $50,000 and $80,000 in upgraded PCs, kits, and add-on components, Dell says.
By the age of 27, Dell became the youngest CEO to have his company ranked in Fortune magazine's list of the top 500 corporations.
At age 20 Larry Ellison dropped out of two different Illinois universities and moved to Northern California.
During Ellison's late 20s he worked at various corporations. Ellison was inspired while working on a database project for the CIA which later led to his own company. It wasn't until Ellison's 30s that the company that we know today as Oracle existed.
During his 20s, Elon Musk graduated from the University of Pennsylvania's Wharton School of Business's undergraduate program he also received a second degree in Physics.
He then went on to attend Stanford University for graduate studies but dropped out two days after the start of school.
Musk started a company with his brother called Zip2 which sold to Compaq for $300 million.
By 28, he started what would later become PayPal and sold it just four years later to eBay for $1.5 billion.