iOS was born without support for multitasking, and when competing smartphone OSes (especially WebOS and Android) added it, it was occasionally mocked for the complexity it adds and the problems this can cause — the fact that a top Android app is a task killer was widely used to mock the whole Android platform, and it’s certainly frustrating under WebOS when you’re told you have too many cards open and need to throw some away before you can do anything new.

Problems iOS users don’t have, true. On the other hand, at least these OSes (a) let you run multiple tasks if you want to, and (b) have explicit support for ending tasks you no longer want for whatever reason. (And there are various reasons to want this: perhaps you don’t want it using resources, perhaps you want it to restart from its default launch state, perhaps you just don’t want it cluttering up your screen.)

Recently I got a new iPod Touch and it’s my first experience both with iOS 4 and with an iOS device with increased memory — in short, now I can try out the multitasking features that Apple added in iOS 4. At first blush, I really like it; it’s easy to switch between recently used apps and recently used apps seem to launch more quickly than they do from a cold start; I think this is a good improvement to the platform.

However, in the next week, I’ve seen at least 2 occasions where apps got in a bad state, and going back to the home screen and relaunching the app didn’t fix it (whereas it would have in iOS versions predating multitasking). Sure, these were app bugs and not platform bugs, but I didn’t know a way to actually quit and restart the app, short of rebooting the whole iPod, or launching a bunch of other apps in quick succession until it magically pages out the offending app so the next time I launch it it’s a clean launch (this is what I did, and it eventually worked).

While writing this post, I looked around a little and it turns out iOS 4 does have a built in task killer — double-tap Home to bring up the multitasking tray with icons for recently used apps, then click and hold on one of these until it wiggles and it’ll have a “–” badge which will remove it from the recently-used tray and, presumably, actually kill it. (Though I still don’t know how to tell which of the many icons that show up in iOS’s multitasking tray — if I scroll to the right, it seems to be a most-recently-used list of every app I’ve ever launched — is actually running.)

So iOS 4 is both more powerful and complex than I’d realized, but also, it’s achieved parity with the oft-mocked Android multitasking feature in both directions — now it has multitasking, but now it needs and has a task killer.

I find I still prefer WebOS’s more explicit interface to multitasking.