The Apple iphone users are all excited because the new iphone-4 has some sort of limited multitasking. But it still just approximates what DOS users had back in the 1980s.
DOS did not get true multitasking until DOS version 6, or versions that had the ability to load a Windows kernel. But long before those, it had the terminate-and-stay-resident command. That allowed user apps to continue to reside in memory and to service interrupts. The best known such app was the Sidekick text editor, but you could also do downloading, CD music playing, print spooling, and other tasks in the background. You could keep text in your editor and paste it into other apps.
You cannot do any of these things with the iphone 1, 2, or 3. There are certain system functions that give an illusion of multitasking, such as a system program that allows you to browse the internet and listen to music at the same time, but you cannot acquire a music-playing app like Pandora and run that at the same time as another app. Worse, you cannot even suspend an app, and later return to its previous state.
The new iphone-4 promises some new features that allow apps to be written so that some limited set of functions can proceed in the background. This reminds me of DOS in the 1980s. Except of course that you could write any DOS apps you wanted, and you never had to get Microsoft's approval. The iphone only allows apps that Apple approves as being consistent with its business strategy. It has even rejected a political cartoonist on the grounds that a politician might be offended. Meanwhile, all the smart phones on the market allow true multitasking. You can have two or more user apps running at the same time, and the system automatically switches among them.
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