Steve Jobs, the founder and chief executive of

Apple Computer

(AAPL) - Get Report

, underwent surgery for pancreatic cancer over the weekend. The 49-year-old Jobs expects to spend the month recuperating from the successful procedure, he told employees in a companywide email.

The stock was down $1.04, or 3.2%, to $31.30. The stock is up from the low $20s in February, a run-up that reflects investor confidence in Jobs' efforts to revitalize the company through a new line of Macintosh computers and the popular iPod digital music player.

Tim Cook, Apple's sales and operations chief, will run the company in Jobs' absence, Apple said. At

Pixar

(PIXR)

, where Jobs is also chief executive, president Ed Catmull will take day-to-day control until Jobs recovers.

"This weekend I underwent a successful surgery to remove a cancerous tumor from my pancreas," Jobs wrote in an email first reported by

Reuters

. "I had a very rare form of pancreatic cancer called an islet cell neuroendocrine tumor, which represents about 1% of the total cases of pancreatic cancer diagnosed each year, and can be cured by surgical removal if diagnosed in time (mine was)."

Jobs noted that he did not have adenocarcinoma, a more common form of pancreatic cancer that isn't currently curable and "carries a life expectancy of around one year after diagnosis."

"I mention this because when one hears 'pancreatic cancer' (or Googles it), one immediately encounters this far more common and deadly form, which, thank God, is not what I had," Jobs wrote.