Current iPhone owners who have an iPhone 3 or iPhone 3GS, are able to update to the newest iPhone operating system ("OS"). 

The iPhone OS4 update was released 2 days before the iPhone 4 was delivered to stores.

What will this get you? All the info after the jump.

Sometimes iPhone updates incremental—like when you sync your iPhone to iTunes and get small fixes or features. Incremental firmware version changes usually will show as an extension number--for example from 3.0 to 3.0.1. When an update for the iPhone changes moves to the next whole number –-like when OS3 came out last year and now to OS4--you can expect BIG changes in the features and functionality of the iPhone.  OS3 brought us copy and paste, the search phone screen, and voice control to make calls or play songs on the iPod app, by simply speaking the command.

Now available, the OS4 update’s improvements take your iPhone 3GS or iPhone 3G to a whole new level with exciting features.  Multitasking, folders, a digital camera zoom, and many more features can breathe new life into your iPhone, answering many of your requests that you don’t feel bad for getting an iPhone and not a Droid.

Here is an explanation of all the features available on the new iPhone OS4 update.