Steve Jobs, along with friends Steve Wozniak and Ronald Wayne, founded Apple on April 1, 1976 to sell the Apple I, a personal computer kit that essentially consisted of a motherboard with a CPU, RAM and semiconductors for rudimentary text-visual processing. Carrying a price tag of $666.66, each Apple I was hand-assembled by Wozniak.

Jobs and Wozniak incorporated Apple on Jan. 3, 1977. Wayne sold his share of the company to his partners for $800.

On April 16, 1977 Apple introduced the Apple II computer, the company's first real commercial success. Sporting color graphics and other advances, the Apple II competed with other early desktop computers such as the Commodore PET and Tandy Corp.'s TRS-80.

In what would prove to be a watershed moment for Apple and the computer industry, Jobs and a number of other Apple engineers visited Xerox PARC (Palo Alto Research Center) in December 1979 to see the office equipment maker's PC, the Xerox Alto. (Xerox, in return, was given the option to purchase 100,000 shares of Apple stock at $10 a share before the company went public.)

The Alto was the first computer to use a graphical user interface and a mouse. The Xerox PARC visit convinced Jobs that the GUI was the key to widespread adoption of personal computers for home and business.

In 1984 Apple introduced the Macintosh, the company's next-generation desktop computer whose development Jobs had overseen and would become the company's flagship product for many years. While not initially a big seller, given its relatively high price tag, the Mac and its innovative GUI was a major factor in the growth of the desktop publishing market.

The Macintosh was announced in a $1.5 million television commercial that aired during Super Bowl XVIII in January, 1984. Based on an Orwellian "1984" theme and directed by Ridley Scott, the ad has become almost as famous as the computer itself.

The success of the Macintosh came on the heels of the commercial failure of Apple's Lisa, which launched in 1983.

Apple hired former PepsiCo executive John Sculley in 1983 to serve as the company's CEO. Jobs and Sculley frequently clashed with their competing visions for the company's future and that led to a showdown in 1985 before Apple's board of directors. Jobs lost out in the power struggle and the board stripped him of his management duties.

Later in the year Jobs left Apple entirely and started NeXT Inc. to design a line of workstations for businesses and the education market.

In 1996 then-Apple CEO Gil Amelio bought Next and its Nextstep operating system and development environment, which would eventually become the foundation for the Mac OS X operating system.

The Next acquisition also brought Jobs back to Apple as an advisor. In 1997 Amelio was fired after Apple suffered several years of dismal financial results and Jobs was named Interim CEO. The "interim" was finally dropped in 2000.

Apple and arch-rival Microsoft shocked the industry in 1997 when they formed an alliance, including a $150 million investment by Microsoft in the financially struggling Apple. Microsoft also promised to develop versions of Office and Internet Explorer for the Mac.

The deal was disclosed during a Jobs keynote at Macworld in Boston in 1997, which included a surprise video appearance by Microsoft CEO Bill Gates.

In November 2001 Apple began selling the iPod portable digital audio player, a wildly successful product (more than 100 million were sold between 2001 and 2007) that presaged the company's success in the consumer electronics market. (In 2007 Jobs would announce that Apple Computer was changing its name to just "Apple Inc." and that computers were no longer the company's main focus.)

Apple also launched its first retail stores and, in 2003, launched the online iTunes store for music downloads. Last month iTunes hit 15 billion song downloads.

In a keynote speech at the Macworld show in January 2007 Jobs debuted the iPhone, a product that would revolutionize the smartphone market. By early this year total sales of the product had surpassed 100 million and quarterly sales have grown to 20 million units.

On Jan. 14, 2009, in an internal memo, Jobs announced that he was taking a six-month leave of absence from Apple for health reasons, specifically citing a "hormone imbalance." Jobs had been treated for pancreatic cancer in 2004 and there was speculation the disease had returned.

But in June Jobs' doctors confirmed that he had received a liver transplant at the Methodist University Hospital Transplant Institute in Memphis.

Jobs returned to work in July 2009.

Entering a market that had eluded other computer makers, Apple introduced the iPad tablet computer on Jan. 27, 2010. Running on the same iOS as the successful iPhone, the iPad quickly became a hot seller – more than 300,000 units were sold on the first day it was available (April 3) and sold 500,000 units by the end of the first week.

By the time of the release of the iPad 2 in March 2011, more than 15 million units of the mobile device had been sold.

On Aug. 24, 2011, Apple announced that Jobs had resigned as CEO, saying he "could no longer meet [his] duties and expectations as Apple's CEO." No other reason was given for Job's decision.

Jobs took another six-month leave of absence starting in January of this year. While he never returned full-time to the CEO job, he made a couple of public appearances, including in March to introduce the iPad 2.

Today Apple has a market capitalization far bigger than any of its competitors and recently vied with Exxon-Mobile for having the largest market cap of any U.S. corporation. More importantly, it's widely seen as the most influential company in the IT industry.

Jobs' departure means the loss of arguably one of the IT industry's most visionary executives.