12 October 2011 Last updated at 18:17

What are key features of iOS 5?

Many diehard fans were disappointed when Apple failed to release the much-awaited iPhone 5 at its recent launch.

Instead they had to make do with new mobile operating system iOS 5 which is available for free to existing iPhone customers from October 12.

Many of the changes are evolutionary rather than revolutionary and show that Apple is, for the time being, concentrating on software.

The BBC has picked out a few of the more interesting changes.

NOTIFICATIONS

With Android handsets eclipsing the iPhone in terms of market share, and Samsung's Galaxy beating the iPhone to the title of best smartphone in this week's T3 Gadget awards, the need to keep up with the opposition has never been more urgent.

This new feature is one that Android users will already be familiar with.

When users receive a message, be it text, email or a missed call, the notifications will appear at the top of the screen and can also be viewed from the home page or when the phone is locked.

It means an end to the current pop-ups which many users found annoying.

iMESSAGE

This is another feature which tips the nod to a rival; this time RIM with its popular Blackberry Messenger service.

The value Blackberry users put on the service was especially apparent this week, as a massive system failure left many angry and frustrated.

Like BBM, iMessage is limited to a single platform, so only iOS 5 users can use it via iPhones, iPads and iPod Touchs.

Users will be able to send text messages, photos and videos with no charge.

For telecoms analyst Ben Wood it is "'iGlue" to lock users in the Apple family.

"Mum and Dad may have an iPhone, while the kids have iPod Touchs and there may also be a family iPad. For them to be able to send short messages to each other from any device is quite exciting," he said.

TWITTER INTEGRATION

Twitter has made it clear that mobile is its key area of growth and it has done a good job of spreading itself to most smartphones.

With iOS 5 adopting Twitter as its default social network, it has scored a major victory.

Tweeters with iPhones will now be able to sign into their account once and tweet with a single tap from camera, photo, contacts, YouTube and the Safari mobile browser plus any third-party apps that support the single sign-up.

The same feature is not available for Facebook, even though the latter has a larger membership. It signals, say experts, a closer working relationship between Apple and Twitter.

CAMERA CONTROL

High performance cameras remain a must-have for many mobile users and the promise of an improved spec on the upcoming iPhone 4S was the one thing that did seem to elicit a gasp from the audience when it was launched.

With iOS 5, Apple shows it is aware that precious seconds could make the difference between a great photo and a missed opportunity.

Upgraded users will be able to take photos without having to unlock their phone and go to the camera app.

A camera button on the lock screen means no delay for serious snappers. Users can also take pictures using the volume buttons.

It is an acknowledgement, thinks Ovum analyst Adam Leach, that Apple wants to support its growing community of photographers.

"The iPhone is the most popular camera among smartphones and this is recognition from Apple that it is an integral part of the device," he said.

NEWSSTAND

A simple feature that shows how Apple 'gets' the need to bring how we organise things in the real world to our gadgets.

More and more people are choosing to read newspapers on iPads but, to date, all newspaper and magazine subscriptions lived in their own apps.

Newsstand brings them together on virtual shelves, as already exists for iBooks.

As well as decluttering how they were previously stored, it shows the value Apple places on digital media, despite the fact that iPad magazines such as Rupert Murdoch's The Daily have so far failed to catch on with many users.

For many publishers, the 30% cut of the cover price which Apple takes may feel like a heavy price to pay, regardless of the exposure it brings.