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SEATTLE -- Topping the wish list for the iPhone and the iPad: broader ability to run more than one program at a time.

On Thursday, Apple Inc. will unveil updates to the software that powers both devices. Although Apple has provided no details, iPhone owners and computer programmers who write applications for the popular smart phone are hoping the company will address their gripes about limits to such multitasking. The matter may escalate as people with iPads, which have larger screens, try to use them in place of more powerful computers.

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The iPhone already allows for some multitasking, but that's largely limited to Apple's own programs. One of Apple's recent commercials shows an iPhone user taking advantage of time spent on hold paying bills, checking e-mail, playing games and then switching back to calling.

But Apple has yet to give users ways to seamlessly switch among all the software "apps" available from outside software companies, the way phones from rivals Palm Inc. and Google Inc. already do.

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So an iPhone user wouldn't be able to listen to music using the Pandora program and check a bank account online simultaneously, for example. In most cases, users must return to Apple's home screen, effectively quitting the open program, before starting a new task.

That's unacceptable to many users and software developers, and full multitasking remains high on many people's wish lists. Because Apple's new iPad runs the same software as the iPhone, changes would apply to that larger gadget as well. Some people have held off buying one because of its inability to run more than one program at a time.

But the reasons Apple is believed to be resistant to broader multitasking -- worries about battery life, performance and security -- remain.

Ross Rubin, an analyst from NPD Group, said he believes those are still big issues for Apple, and he doesn't believe full multitasking will be among the changes in the iPhone operating system to be announced at Apple's Cupertino, Calif., headquarters Thursday. Apple did not immediately answer requests for more information about its plans.

Apple has given software developers limited ways to work around the multitasking restrictions, such as allowing them to send very basic notifications nudging iPhone users to open an app for updated information.

Some people hope that if Apple doesn't add multitasking, it would at least make the notifications less intrusive. Now, if a notification comes through, users must deal with it or dismiss it before returning to what they were doing.

The last time Apple made a major revision to its iPhone operating software, in March 2009, it added features that many iPhone users had been clamoring for since the device launched two years earlier. Those features included the ability to copy, cut and paste, and a search function that worked across all programs.

But this time, beyond multitasking, there seemed to be fewer big-ticket requests from everyday iPhone owners.

The new version of the iPhone system that Apple is announcing Thursday, likely to be known as OS 4.0, probably won't be available for a few months. Most of the changes would have immediate appeal to software developers, not regular users, said Charles Golvin, an analyst for Gartner Inc.

Golvin believes Apple is likely to launch a system for delivering ads to iPhone and iPad apps, reflecting its January acquisition of mobile advertising company Quattro Wireless.

Although many of the changes Apple makes to the iPhone software will take awhile to translate into benefits for the average iPhone user, the most committed Apple watchers and bloggers have been honing their iPhone wish lists.

They want, among other things, a unified inbox for all e-mail accounts, support for more e-mail folders, wireless synching with a computer and a way to connect an iPhone with a regular keyboard, by plugging one in or using Bluetooth wireless technology.

But as is always the case, predicting the next move by secrecy-obsessed Apple is next to impossible.

"It's Apple," Golvin said, "so who ... knows what actually could come out."