In the new ecosystem, many rules are still being worked out. Amazon, with its Kindle tablet and a successful online computing cloud and software store, may yet be a significant player. So may Barnes & Noble, which has a decent tablet and apps in the Nook reader but lacks a big cloud data center.

A few things are already clear. Power now centers on controlling millions of computers tied together in the cloud, with a complementary marketplace where people can find, sell and manage applications. Few physical stores sell software anymore, but sales channels still matter. Even the iPhone did not really take off until it had apps, sold through Apple’s store.

Those apps were written mostly by outside software developers. Developers have been important to the industry for decades. If you keep thousands of them happy with decent software-making tools and a big potential audience, as Microsoft learned, they will build products that make you essential. When the PC came along, these were games like Flight Simulator and productivity software like Lotus; now we have Angry Birds and modifications of Google Apps.

In the Wintel world, new versions of Microsoft Windows came out every few years, with major software projects tied to desktops and laptops. By contrast, in less than five years Apple has announced six versions of its mobile operating system. Google’s operating system for cloud-connected laptops, called Chrome, is updated every six weeks. The June meetings were intended to get developers working on consumer products that would be out by Christmas.

“Urgency has a whole new meaning now; you can’t slip,” said Andy Peterson, a senior software engineer at L4 Mobile, which makes mobile applications for companies like Sony and MTV. He was one of 5,500 developers at Google’s I/O conference last week. “I started at the company last September,” he said, “and I’m on my fourth application.”

Still, he says, the pace and the ability to get a creation into so many hands is exciting.

Dell and H.P. might not be joyful, but should they be glum? With so many devices, the consistent experience may be guided by centrally managed cloud software, but hardware is where the experience lives. That is why Steve Jobs was so long adamant that Apple control both hardware and software, and why even now Apple is picky about which independently produced apps are allowed in its store.