Every iPhone and iTouch runs a version of iPhone OS. It’s the software that runs “behind the scenes” to show you the home screen with the list of your applications, to let you install and delete apps, and to do all the other bits of housekeeping that you don’t see. iPhone OS is the iPhone/iPod Touch equivalent to Windows on your PC (or OS X, if you use a Mac).

Sometimes you need to know what version of iPhone OS you are running. Usually this is to make sure your version is new enough for a piece of software.

So, how do you know what iPhone OS you’re running? Luckily, there’s no special skill needed here, and there’s even two equally simple ways to do it!

Find Your iPhone OS Version With iTunes

Plug your iPod Touch or iPhone into your computer by whatever means you usually use to synchronise your device – the cable or a dock.

Now go to the iTunes program on your computer. If the screen isn’t showing your device’s information, click on the name of your device. You can see mine in the is called Touchy – it’s in the red circle I’ve drawn on the left of this picture:

Here's the device page for my iPod Touch, with the version number in the red circle.

In the red circle on the right you’ll see the heading “Software Version” and mine says “3.1.3″ – that’s my software version. Unless you have a very old iPod Touch or iPhone, yours is probably the same version.

Find Your iPhone OS Version With Your iPhone/iTouch

This takes a few more button presses but you can do it without having a computer handy. First, turn on your iPhone or iPod Touch and unlocking it so you can use it. You’ll see the screen with all your application icons, one of them will have the name “Settings” and an icon that looks like this:

This is the icon for the Settings app, it will be on the first page apps on your iTouch or iPhone.

Now select “General” settings:

Now you're in the Settings app, you need to go to the "General" section.

And now the “About” section:

This is the general settings page, now you need the "About" item.

And now you need to scroll down to the bottom of the list and you’ll see “Version”:

And now you just read off the version number - ignore the bit in brackets.

You can safely ignore the bit in brackets, so the version here is “3.1.3″.

Understanding The iPhone OS Version

So now you know your version number, how do you understand it?

Firstly, if you read it out you pronounce the “.” parts as “point”. So “3.1.3″ reads as “Three point one point three”.

Version numbers read from left to right like regular numbers, but the leftmost number is always the most important. So “3.1.3″ is a bigger version number than “2.2.4″ the way “313″ would be higher number than “224″. The only reason we need dots at all is that sometimes a single part gets higher than 9, so “2.10.1″ is a valid version number and is higher than “2.9.8″ but lower than “3.0.0″. And “2.10.1″ would be a different version to “21.0.1″ and to “2.1.01″.

Since the leftmost number in the version is the most important, you have to imagine inserting any “missing” zeroes – for example “2.1.0″ is the same as “2.1″ and “3″ is the same as “3.0.0.0.0.0.0″

And if that all sounds horribly confusing, mostly it’s just the first one or two numbers that matter. So if your version number begins with a “3″ then it’s higher than any version number beginning with “1″ or “2″. So I can look at this requirements list:

Now you can compare your own version to the required version.

It says that it requires iPhone OS “2.1 or later” and I know my version number is “3.1.3″ which starts with a “3″ so that’s higher than anything starting with a 2, including “2.1″ so it must be a later version so I know I can run this app on my device!

Practice: Look up your version number by both of these methods and leave a comment telling me how you went.

Cheers,
Jeshyr