For millions of Apple fans, Steve Jobs is irreplaceable. But if there's one man Jobs himself trusts to stand in his shoes, it is his second in command, Apple Chief Operating Officer Tim Cook.

With Jobs on medical leave until June, Cook will be leading the team at Apple. And it is likely that when Jobs leaves Apple, it will be Cook he will anoint as the new CEO of the company.

"Tim runs Apple," says Michael Janes, the first general manager of Apple's online store and now co-founder of ticketing search engine FanSnap, "and he has been running Apple for a long time now."

"Steve is the face of the company and very involved with product development but Tim is the guy who takes all those designs and turns it into a big pile of cash for the company," he says.

In some ways, Cook and Jobs are poles apart. Cook is the yin to Jobs' yang. A quiet, soft-spoken, low-key executive, he couldn't be more different from Jobs' sarcastic, fearsome, larger-than-life personality. But that's exactly what makes him perfect for the job, say people who have worked with Cook.

"He has an analyst's mind and is very organized and action oriented," says Janes. "A few years ago Larry Bossidy came out with a book called 'Execution'," says Janes. "That book could have been Tim Cook's Bible, it could have been his biography."

What Cook and Jobs have in common is a passion for making Apple products the best, the ability to set high standards and an incredible level of attention to details.

Wall Street analysts, former executives and Apple resellers are unanimous that Cook is an operational whiz. His attention to the nuts and bolts of the business has helped make Apple incredibly profitable. Last quarter Apple posted profits of $1.14 billion on revenue of $7.9 billion.

Apple's highest-paid executive, Cook joined the company in 1998 as senior vice president of operations and was promoted to worldwide sales lead in 2002.  Before joining Apple, he was responsible for procuring and managing Compaq’s entire product inventory.

Kevin Langdon, CEO of Crywolf, an Apple Specialist reseller firm, first saw Cook giving a sales presentation to Apple resellers.

"It was his first introduction to the channel and he seemed like very low-key, affable but scary-smart," says Langdon. In a way, Cook was the very opposite of his predecessor, Mitch Mandich, who was more loud and outgoing, the "prototypical" sales executive.

Over the next few years, Langdon and other resellers watched Cook change how Apple ran its business. Inventory on hand, a crucial measure for a company that indicates how fine-tuned its supply is to market demand, went from weeks to sometimes 16 hours, says Langdon, indicating a far more responsive company.

It's one reason why Apple has been so successful. In the consumer electronics business, new products are announced frequently and their introduction has to be managed carefully. One premature leak, and consumers may stop buying current models in anticipating of the newer ones still to come — potentially causing millions in losses due to built-up and unsold inventory.

Cook helped perfect inventory management to the point that Apple, which regularly launches big new products, has few of the older ones left at the end of each cycle. It helps the the company avoid the trap of having to significantly discount older products.

"Tim made Apple's operations the best in the industry in a short period of time," says Langdon. "He tightened up procedures to be more efficient and made the process predictable."

Cook's genius didn't go unnoticed at Apple, where he was soon asked to lead the company's Macintosh division and in 2005 became the chief operating officer at the company.

Extremely organized, Cook's job at Apple is his life. He is known to have meetings running late into the night. Janes says he has been on calls with Cook at midnight and 5 a.m., especially when working with partners in Asia and Europe.

"Though Tim seems laid-back, he is relentless in terms of energy," says Janes. "He is known for his multi-hour staff meetings going through all the details."

And like his boss, Cook is a health nut, chowing down on energy bars and bicycling and weightlifting to keep himself in shape.

"When he is not working, he's working out," says Janes.

Details about his personal life are scarce and even executives who have known him for years say they rarely saw him outside work.

Read the full post