Much of the media we use is acquired, stored and accessed though the 'cloud'.
'Where did the computer go?" was the slogan Apple used in 2004 when it launched the first of its current range of iMac desktop computers. The question was designed to draw attention to the ingenuity with which the company's designers had managed to pack the components of an entire desktop computer into what was effectively an enclosure for a large flat screen. But actually it's a question with a more contemporary relevance, because nowadays most of us rely on "computing" that's provided by machines we never see and could not locate even if we tried. They are somewhere out there in the internet "cloud" (so called because the network is often drawn as a cloud in technical diagrams), which is how so many of us came to be users of something called "cloud computing".
It's very different from how things used to be. Once upon a time the computer was the PC (or the laptop) on your desk. If you wanted to do word processing, or calculations on a spreadsheet, or to read and write emails, you did so by launching a program that ran on your computer. And the data – the documents, calculations or messages – that you produced were likewise stored on the hard drive inside your machine. Even if the PC was connected to the net, most of your computing activity happened inside the box on your desk.
And now? First, most of what we think of as "computing" is increasingly done using a smartphone or an iPad or a simple, stripped-down, laptop or "netbook". Much of our data – documents, emails, photographs, spreadsheets – is no longer stored on our devices but is held in distant server farms operated by the likes of Google, Yahoo, Facebook, Amazon and Microsoft. And if you're a serious user of computing resources you will not only store your stuff in the cloud, but rent virtual computers from companies such as Amazon on which to run your own programs.
What made this possible was the penetration of broadband – ie internet connections that were fast enough to ensure that interactions with distant machines happened at a tolerable speed. Once these types of connections became widespread, the die was cast.
For individuals, reliance on cloud computing came about mainly because companies such as Microsoft, Google and Yahoo offered useful services – think search (Google, Bing), webmail (Hotmail, Gmail), image hosting (Flickr, Picasa) and social networking (Facebook) – that were apparently free (ie supported by advertising) and required no special software (other than a browser) running on their computers.
For companies, the route into dependence on cloud computing was driven by economics. Building and running IT services for thousands of employees is an expensive and unrewarding business. But for several decades companies had little alternative – just as a century ago they had no alternative except to build and operate their own electricity generators. But eventually it became possible to purchase electricity off the grid, and so most companies shut down their generators and left the messy business of producing electricity to utility companies. Now they're doing the same with computing services, which they regard as a utility – just like electricity or water. In other words, the net has become another kind of grid. JN
Apple / iCloud
Key features iCloud launched in early October, promising a simple and elegant way to store music, photos, documents and other files on Apple's servers and then access them from iPhone, iPod touch, iPad and computers. The key point is that a lot of this is done automatically in the background without you having to do anything. For example, a feature called Photo Stream makes all the photos you take appear on your other devices for up to 30 days.
iCloud also lets you download all your previous purchases on Apple's iTunes Store to your Apple-registered devices. Meanwhile, developers making apps for Apple devices can also use iCloud's storage. Early examples include game saves being accessible across iPhone and iPad, and document editing apps working across all these devices.
Devices iCloud works on any iPhone, iPad or iPod touch running the iOS 5 software, as well as any Mac running the OS X Lion operating system. But it also works on PCs, through iTunes.
The cost iCloud is free with 5GB of storage space for your content, although anything you buy from iTunes doesn't count towards this total, nor do your Photo Stream pictures. 10GB of additional storage costs £14 a year, while 20GB costs £28 and 50GB costs £70.
Ease of use The key to iCloud is that, often, you don't have to "use" it: the service does things in the background without you needing to upload or download anything. The idea being that quickly, you'll just assume your files and content are available on whatever device you're using at the time.
Privacy and security iCloud involves a lot of your personal content being sent over the internet and/or stored on Apple's servers, although the company uses encryption technology to keep it secure. Apple also has a policy of only storing location data from individual devices for 24 hours on its servers before deleting it.
Great for… Anyone with an Apple device, but particularly for those with two or three. SD
Microsoft / SkyDrive
Key features Microsoft's SkyDrive is part of its Windows Live service, with strong links to services such as Hotmail, Windows Messenger and Xbox Live. It's more of a virtual hard drive in the cloud, using a similar system of folders to organise your stored files.
You can store documents, photos and videos in your SkyDrive, as well as other files. Documents can be edited within Microsoft's Office web apps – just like Google. Meanwhile, Hotmail is the basis for synchronising your contacts, email and calendars across all these devices.
SkyDrive also has the ability to make certain folders public – to share their contents with friends and family, for example. This feature is useful for workmates collaborating on big documents or projects. Like Apple, Microsoft wants developers to incorporate SkyDrive into their apps, both on PCs and Windows Phones.
Devices SkyDrive is accessible from PCs and Macs, but also from smartphones running the Windows Phone operating system. It has a good mobile website, too, which works on other mobile devices.
The cost SkyDrive is free, and you get 25GB of storage for your documents and files. At the time of writing, there is no way to buy additional storage.
Ease of use One easy way to use SkyDrive is from within Microsoft applications, such as the latest version of Office, which lets you save documents directly to your SkyDrive. It's also integrated into Windows Phones, allowing you to save photos to your SkyDrive immediately after taking them. Using the main website to upload and access files is simple, too.
Privacy and security Microsoft gives every file you store on SkyDrive its own web address, making it easy to share them with friends – and the URLs are long and complex enough not to be guessed. You can also set files and folders to share with specific contacts or to be entirely private.
Great for... Anyone with a Windows Phone and the hardy people who are still using Hotmail in 2011. SD
Key features Google has a number of cloud services that increasingly interlink. Gmail, for example, now offers an impressive 7.6GB of free storage for emails and attachments, while also storing your contacts.
Another Google cloud service is Google Calendar, which stores your engagements in the cloud so you're never far from a device telling you when your dentist appointment is.
Google Docs is for creating, editing and sharing documents, spreadsheets and presentations – an online equivalent of Microsoft's Office (although in response to Google Docs, Microsoft now has one of those too).
Google eBookstore is a cloud service for buying ebooks and accessing them from any web-enabled device, while the company has a music service live in the US, and coming our way soon.
Devices Google makes its cloud services available across every device possible: computers, tablets and smartphones. On the latter two, this is a mixture of apps and (often superior) mobile websites. They work particularly well on devices running Google's Android software.
The cost All Google's cloud services are free. That said, if you find yourself bumping up against the upper storage limit on Gmail, 20GB costs $5 a year, 80GB costs $20, 200GB costs $50, 400GB costs $100 a year and 1TB will set you back $256.
Ease of use Google's experience shines through: its services are easy to use, with Google Docs presenting no problems for anyone switching from desktop tools such as Office. Over time, the different services have also linked together in some good ways, such as prompting you to make a calendar appointment from within Gmail.
Privacy policy Google's policy of selling ads relating to keywords in your emails can spook new Gmail users, but the company says its systems are entirely automated – and are also used to screen out viruses and spam from your inbox. Security-wise, Gmail can offer a two-step verification process to enter an additional code when logging in.
Great for... Cost-sensitive web users who buy into the Googleplex dream. SD
Dropbox
Key features Dropbox is the independent option in the four main cloud services we have chosen: it's a startup that doesn't make its own devices or operating systems. Its pitch
is simple sharing, with files saved to Dropbox made instantly available across all your other devices.
Other key selling points are the fact that Dropbox works when you're offline because the files are actually stored on your devices, but it also keeps data usage to a minimum – important for mobile users – by only transferring the parts of files that change when you edit them.
Dropbox also includes sharing features to give friends, family and colleagues access to specific folders, so that it'll feel like that folder is stored on their computer too. You also have a Public folder where every file has a link for anyone to view.
Devices Dropbox works on just about anything: its website is fine for PCs and Macs, while it has apps for iPhone, iPad, Android and BlackBerry. Phone users can edit files and then upload their photos and videos.
The cost Dropbox is free at its basic level, which provides 2GB of storage for your files. You pay $9.99 a month for the Pro 50 package (50GB) and $19.99 a month for Pro 100 (100GB).
Ease of use Dropbox has been designed to be easy to start using straight away, even if you're not a geek. The focus is on simplicity, from uploading files to sharing them with others. From the moment that your different devices are set up to synchronise your files, it's seamless.
Privacy policy Dropbox caused a stir earlier in 2011 with a change to its terms and conditions taken by many people as a claim to ownership over the files stored on it. The following week, however, it clarified to users that "You retain ownership of your stuff… We don't own your stuff."
Great for… Independently minded souls with a range of devices from different manufacturers. SD
Cloud atlas: Specialist providers
Photos: Digital cameras and smartphones mean a lot of people have thousands of photos stored on their computers. Why store them in the cloud too? Partly to make them easier to share, but also for security: a back-up in case your hard drive comes a cropper.Flickr is the best-known cloud photos service, although in recent years it has faced serious competition from Facebook. You can upload to Flickr from your computer or mobile device, and it now makes it easier to post them on social networks too. Rivals include Photobucket and Picasa Web Albums, although now there are also mobile cloud photo apps such as Instagram and Picplz, which let you apply a range of visual effects before sharing.
Music: Apple's iCloud will soon be the most high-profile cloud music service in the UK, but there are already rivals available.
Sony's Music Unlimited is one of the best, because it combines the ability to store your existing music collection in the cloud with a Spotify-style library of songs you don't own, to stream. It works on computers, but also Android devices and the PlayStation 3 console.
Carphone Warehouse also has a cloud music service, My Music Anywhere, which stores your collection online, including playlists, and allows you to access it from other computers and your smartphone.
There is also US service MP3tunes, which is controversial within the music industry (record label EMI sued it), but it was one of the first to offer a music locker, with 2GB of free storage and more for customers who pay.
Games: When it comes to games, the term "cloud" means something different. It's not about uploading your games to a remote server, but about never having to own the games in the first place: no downloads or discs required. Your chosen game runs on OnLive's server, delivering video to whatever screen you're playing on – PC, Mac, TV or tablet – then transmitting your controls back up to the server. One key advantage is that you don't need the most powerful hardware to run even the latest, most graphic-intensive games.
To play on a TV, you'll need the OnLive Game System (a set-top box and joypad) which costs £69.99 plus subscription at £6.99 a month, although you buy access to brand new games separately.
One rival is Gaikai, which aims to strike deals with websites to make games and demos playable within the web browser.
Cloud hardware: The lowdown
Most of the talk around the cloud concerns software and websites, but increasingly there is hardware too. Google's Chromebooks are laptops designed to be used with the company's cloud services. They even boot up straight into the web browser. Amazon's Kindle Fire tablet works with that company's cloud services. It goes on sale in the US this month, but no UK release date has been set.
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