Apple CEO Steve Jobs, 56, deemed irreplaceable by millions of fans of the operating system, died on Wednesday due to his long battle with a rare form of pancreatic cancer, beginning in 2004, when he underwent transplant surgery for it.

Jobs, who resigned as Apple's CEO in August, is said to have changed the course of personal computing during two stints at Apple that transformed the mobile market.

The circumstances of his passing were unclear, but many believe that Jobs' death was caused by his battle with aggressive cancer and other health issues.

The world rarely sees someone who has had the profound impact Steve has had, the effects of which will be felt for many generations to come, Microsoft co-founder and long-time rival Bill Gates, told Reuters.

Jobs, a college dropout, reportedly traveled through India in search of spiritual guidance prior to founding Apple, a name he suggested to his friend and co-founder Steve Wozniak after a visit to a commune in Oregon he referred to as an apple orchard.

For those of us lucky enough to get to work with him, it's been an insanely great honor, Gates added.

Fans and supporters flocked to Apple stores to pay the innovative thinker respect and honor Jobs' dent made in technology industry. Jobs' family thanked many for their prayers during the last year of Steve's illness.

According to the National Institutes of Health (NIH), some pancreatic cancer patients can have their tumors surgically removed or cured.

Although, in more than 80 percent of patients the tumor has already spread and cannot be completely removed at the time of diagnosis.

In 2004, Jobs' tumor was removed in a successful procedure, however, the malignancy had spread beyond the pancreas and, in 2009, Jobs took another leave of absence to undergo a liver transplant.

Finally, he took his third leave of absence in January of this year, before resigning as CEO in August.

With a very low survival rate of four percent, pancreatic cancer is the fourth most common cause of cancer death in the U.S., as well as across the world, according to the NIH.

And 95 percent of those diagnosed with this cancer will not be alive five years later.

There are two known types of pancreatic cancer - adenocarcinoma and neuroendocrine tumor. Jobs was affected by the latter, an extremely rare form with a prevalence rate of 35 affected patients per 100,000.

Must Read: Steve Jobs is Dead: Top 10 Biggest Achievements of Jobs During His Lifetime (PHOTOS)