As expected, Microsoft is using its Build developer conference to distribute a pre-beta, developer preview version of Windows 8 (for x86 PCs only; the hardware to run the ARM version on isn't finished yet).
In Depth: Hands on: Windows 8 review
Windows 8 is Microsoft's combined desktop, laptop and tablet operating system, designed to go from 10-inch touch-only tablets to big screens in your living room, from ultra-portable notebooks to massive gaming systems and business desktops.
It's got the Windows Phone 7 Metro-style touch interface of live tiles, the Metro programming model for building web apps and native apps that run full screen and share information.
Windows 8 also features gestures to put two apps on screen side by side, and the traditional Windows desktop for when you need richer apps like the ones we've been using in Windows for years.
That's a combination no other single operating system can offer - but how well does it work?
The inspiration of Windows Phone 7's Metro interface is clear in the interface for the Windows 8 Lock screen and Start screen (which completely replaces the Start menu).
But this isn't a slavish copy of the phone operating system look.
It still has the live tiles and the personalisation, enabling you to pin people, RSS feeds and web pages alongside apps. But it's more colourful, more flexible and better designed, to enable you to arrange and explore large numbers of apps.
Windows 8 interfaceYou can customise both the image you see on the Windows 8 Lock screen and the details of unread emails and missed instant messages that it shows. And you can pin desktop apps such as Office or Task Manager, and even a link to the desktop, to the Lock screen.
You can group tiles together - giving groups a name or leaving them blank - and make any tile single or double width. Just swipe the tile up a little to get the option to change the size, unpin the app or uninstall it completely.
You'll be able to do that for pre-installed Metro software too (which is what Microsoft is encouraging OEMs to bundle on new Windows 8 PCs).
As well as moving a tile to a new location by dragging it, you can also drag it up to the top of the screen with one finger and hold it there while you swipe across the screen to get to where you want to drop it - a much easier way of dealing with a long list of tiles.
Future builds of Windows 8 will also enable you to pinch to zoom out so you can see all the tiles on screen at once, and rearrange groups at the same time.
Once you launch apps, you can use gestures to arrange them. Swiping from the left switches to the next app, but you can also swipe and drag to put two apps on a screen side by side - and one of those can be the Windows desktop.
There are only three window sizes for apps arranged like this (counting full screen), so that developers don't have to worry about making an infinite number of layouts look good. One app is a thin QVGA 'snap' view on either side of the screen, and the other is a larger VGA full view - which is why this only works on 1366-resolution widescreen PCs.
But if the Windows 8 desktop is in full view you can still use Aero Snap to arrange two windows, and if it's in snap view you get thumbnails for all the running desktop apps that you can tap to open.
This is a good combination of enabling you to use two apps at once on a tablet. This is something only the occasional dual-screen Android tablets enable you to do, and then only for a limited number of apps. It also makes it easy to switch from Metro apps to desktop apps and back.
Swipe in from the right of the screen and you get what Microsoft is calling the Windows 8 "charms": search and share, which work across different apps; devices and settings; plus a button for switching between the Start menu and the desktop.
The Settings charm gives you the settings for the current Metro application plus options for volume, brightness, notifications, networking, switching language and choosing to sleep, shut down or restart.
It's great to have one place to do that in every application. It's also a logical place for commands such as Restart that used to be on the Start menu, because there was nowhere else to put them. We kept looking in there for a link to the Control Panel, which is currently just a tile on the Start screen.
It would be more logical to put a link here for more settings, in the same way that the friendly Control Panel interface organises the most common options clearly, with a link to the desktop control panel for other settings (and you can still search for specific control panels just like searching for an app or file).
Open an app that needs the Windows desktop and you get the familiar desktop view with Recycle Bin, task bar and Start button.
But the Start button opens the Start screen again - the Start menu is gone in Windows 8.
The look of the desktop and desktop apps will change before the Windows 8 release date. We're expecting the new-look Task Manager to be a clue to the final interface style, but the ribbon makes an appearance in Explorer. This is always controversial, but we think it works well for organising options and tools together.
If you use multiple monitors, you finally get better desktop management. You can have the Start screen on one monitor and the desktop on the other, which keeps the two interfaces separate.
But if you're using multiple screens it's more likely you're using desktop apps, so you'll like the option to duplicate the task bar on both screens or pick which icons you see on the task bar for each screen. You can also finally put a different desktop background on each screen.
Windows 8 searchThere's no Start menu in Windows 8, but you can search as if it was still there. Hit the Start button on the keyboard (or on a tablet PC) and start typing. The results you see on screen are for apps, so you don't have to go swiping through the tiles to launch programs. But you also see if there are matches in settings or file names.
You can pick apps that you can search directly here, including social and music apps and Internet Explorer, which searches on Bing.
This is the way sharing works too; choose the Share charm and you can pick a contact to email or a social app that has signed up for sharing, so you could send a tweet or upload a photo to Facebook the same way from any Metro app. How successful this is depends on how many apps use these features, which is something developers have to build into their apps.
Internet Explorer 10 on Windows 8IE10 runs in Windows 8's Metro interface as well as the desktop. If you want to change settings - such as turning on the Tracking Protection Lists or saving a favourite or home page - you'll need to swipe for the app bar and tap the button to open the page on the desktop.
Swiping also shows the address bar and the list of open tabs. Press the '+' button to open a new tab; press and hold to open a new tab for InPrivate browsing that doesn't save cookies or history. Most of the time that's all you need from a browser, so IE 10 works very well as a Metro app.
It also works well as a modern browser - it has the vast majority of usable standards in HTML 5 and CSS 3, it's fast because of the hardware acceleration and it has excellent security thanks to SmartScreen.
Internet Explorer 10 in Windows 8 also still has Flash, Silverlight and all the other plug-ins that other tablet browsers often lack.
Windows 8 applicationsMetro apps don't have to work the same way in Windows 8 as Microsoft apps, but some things are consistent. Swipe up from the bottom of the screen or down from the top and the app bar and any controls appears. This is similar to the Windows Phone 7 menu gesture, but is better suited to the larger screen.
The developer preview has a couple of dozen Metro apps, from utilities for setting alarms to games to the obligatory Facebook and Twitter tools.
One of these is a media app, which is fun but basic. We haven't yet seen Media Center or Windows Media Player or Zune for Windows 8. You can paint with your fingers, handwrite notes and reminders, or waste hours reading RSS feeds laid out like magazine pages.
These Windows 8 apps were written by Microsoft interns in 10 weeks this summer, and they range from pretty but basic (Tweet@rama isn't going to replace Seesmic) to accelerometer games that are huge fun to play.
They're very like Windows Phone apps scaled up, and they're easily better than many trivial apps for Android tablets and the iPad. While they don't match the best apps on other platforms, they bode well for what developers with more time and inspiration will be able to deliver.
The Live apps for Metro look impressive, although again they're not in this Windows 8 pre-beta developer preview build.
The Mail app has a very Windows Phone look, but uses the widescreen space well to show folders or accounts as well as your inbox and messages.
The calendar app has a nice two-day view as well as week and month views, and overlays multiple calendars from Windows Live.
The People app aggregates your contacts from Windows Live, Facebook, Twitter, LinkedIn and Exchange. It looks remarkably like the Windows Phone version, down to the icon for linking contact entries that are the same person.
The Photos app grabs your pictures from Facebook and Flickr as well as SkyDrive, and even from PCs that you connect to remotely through SkyDrive.
Windows 8 app creationDesktop Windows apps are the same Windows apps they've always been, at least on x86. At this point, although we've seen a prototype ARM Windows version of Office, Microsoft is saying that all ARM applications will be Metro apps.
Metro apps run in their own sandboxes for security, and while they can use your location - if you give them permission - access files and share information with other apps, that's limited to accessing documents and pictures rather than being able to get at the whole file system.
The developer tools for creating Metro apps are the same powerful tools Microsoft has for writing standard Windows programs and Windows Phone apps, but with templates for the Metro layouts. These include full screen, snap view and full view in landscape and portrait at different screen resolutions.
This broad language support should reassure developers who have been complaining about lack of Silverlight support since ex-Microsoft server chief Bob Muglia suggested last year that Silverlight was being sidelined. We're not sure why Microsoft didn't come out and explain the position much earlier.
Now developers can concentrate on building interesting apps, and we're looking forward to seeing what they come up with.
Windows StoreWe've seen a preview of the Windows Store, but it's not in the developer preview of Windows 8. The Store is a Metro app that looks similar to the Windows Phone Marketplace, but it'll include desktop apps as well.
You can search for something specific or browse the categories, which highlight new apps as well as top rated, top free and top paid apps. Developers can offer trial versions and see how popular their apps are and what errors have been reported.
Windows chief Steven Sinofsky suggested that Microsoft would also learn from Apple's mistakes and allow in-app purchasing, but there's no news on what the charges to developers will be.
Windows 8 cloud integration and synchronisationInstall an app from the Windows Store and it will show up on all your PCs. Give it a Live account and Windows 8 will also sync settings between all your PCs. It'll sync your desktop background, lock screen, what you have pinned to the task bar, IE favourites, passwords and your browsing history so you can find the page you were looking at, whether you opened it at home or at work.
You can also use SkyDrive to access one PC from another, remotely over the web, even if it's behind a firewall. This is how the Photos app will be able to get images from your different PCs.
Metro apps can also sync information using SkyDrive, although if they have a lot of data they have to ask permission before they fill up your space. Desktop apps can do the same, but coding that up isn't as simple.
On-screen keyboard and handwriting recognitionWindows 8's multi-touch on-screen keyboard is a big improvement over what you get in Windows 7.
Fuzzy hit targeting (which we explain in the Windows desktop and touch section below) makes it far more accurate.
It also has excellent auto correct for common mistakes. Sometimes it suggests a change but doesn't make it automatically - if you type a real word but you could have meant to type something slightly different.
And to make it faster, you can hit the Insert key rather than having to move your finger to select from the menu. You'll also see the familiar red squiggly underline for spellings Windows doesn't recognise and can't fix.
For faster typing when you're holding a tablet in both hands, you can split the keyboard in half and type with your thumbs. Although the keys look far too small, this is also remarkably accurate.
Or you can use handwriting. The writing area is far less fiddly than in Windows 7, with plenty of space over two lines. Your handwriting is converted straight into text, but select the text if it's wrong and you can correct or rewrite it.
Windows 8 apps can also use ink that keeps your writing but recognises the text, just as in Windows 7 - there's a simple Metro ink application as well as the Windows Journal. Unless your handwriting is really bad, recognition is generally accurate.
Windows 8 desktop and touchEven on the highest touch resolution Windows 7 screens (and few Windows 7 tablets have high touch resolution screens), touching the tiny icons in toolbars can be hard. Even closing a window by touch is a hit and miss affair.
Although the Windows 8 desktop looks substantially the same and tiny buttons for the notification area still look tiny, Microsoft has done a hugely impressive job at making it easy to accurately select things on screen with touch.
Tap the notification button and you don't open the on-screen keyboard or Action Center instead, even though they're mere pixels away.
Swipe to select a range of files in Explorer by dragging your finger over them and they select neatly, with checkboxes next to them to make it easy to remove anything you don't want.
The Explorer ribbon buttons and options aren't particularly big buttons, but we could select the ones we wanted every single time, and it was easy to select entries in Task Manager.
The secret is something called 'fuzzy hit targeting' which works the same way the touchscreen keyboard does on Windows Phone 7, detecting where it's most likely that you meant your finger to go.
The software developer has to interpret that to pick the right button. Microsoft has done an excellent job of that for standard Windows controls such as minimising, maximising and closing buttons or expanding a folder tree in a file dialog (another tiny triangular button we could touch accurately every time), as well as for the ribbon and other Windows components.
The test will be how well that works on a wide range of third-party applications where it's up to the developer to deal with the information from Windows 8 touch, so we expect Windows 8 tablets to come with pens.
The converse of touching what you want is not touching what you don't want. In particular, you don't want to worry about resting your hand on screen while you're writing with a pen, which for most of us is the only way to write neatly (and you need to be reasonably neat for handwriting recognition to work).
Windows is the only tablet operating system that handles palm rejection, blocking the brush of your hand on screen as you write.
We haven't seen this in operation on an ARM tablet yet, but Microsoft says the handwriting recognition will work there are well.
Windows 8 securityWhen you first turn on a Windows 8 PC it asks if you want to use a Windows Live account with it. Say yes and that becomes your Windows account, with the same username and password.
If you don't want to type that in on a touch screen every time you unlock your PC, you can use a PIN or set a picture password. Choose a picture and draw three gestures on it - it could be a smiley face on a photograph or three squiggly waves on a picture of the ocean, or whatever you'll remember to draw every time you see the photo.
That's a nice combination of easy to remember and easy to do, and it's also secure enough to protect you. With the number of fingerprints we put on the screen in just a couple of hours, your password gesture won't stand out the way some unlock gestures do on smartphones.
Windows 8 repairHardware fails and PCs crash. And sometimes Windows gets in so much of a mess that it's easier to start from scratch. That's all easier to deal with in Windows 8, with yet another Metro-style interface.
This enables you to choose between a full reset and a refresh. A full reset requires an admin account, because it formats the drive and deletes all your data. A refresh installs a clean copy of the Windows 8 operating system but keeps your files, favourites, pinned tiles and applications.
Windows 8 networkingThe new Metro Settings charm and control panel make it very easy to connect to Wi-Fi or mobile broadband, with built-in drivers for 3G dongles as well as built-in radios.
Windows 8 will automatically use the fastest connection, and it knows that you have to pay for mobile broadband and keeps track of what you're spending.
It won't download Windows Updates on your 3G connection and it can automatically use less bandwidth - for example telling photo apps to send low resolution thumbnails rather than full images.
Windows 8 performanceIt's hard to judge the performance of code that's this early in development, but running Windows 8 on a recent notebook gave the same excellent performance as Windows 7, at least for desktop apps.
Cold boot and full shutdown are both impressively fast, even on hard drive systems (not just with an SSD).
If anything, the system requirements for Windows 8 are less demanding than Windows 7, thanks to the need to write code that can run on an ARM tablet. Microsoft tells us to expect slightly improved battery life on x86 laptops compared to Windows 7, too.
The minimum spec is a 1GHz processor, 1GB of RAM (2GB for 64-bit PCs), 16GB of disk space (32GB for 64-bit) and DirectX 9 graphics with WDDM 1.0.
The system tries to save on memory by sharing it between applications rather differently. Because a lot of apps use the same libraries and runtimes, they can have a lot of the same code in memory. So whenever Windows 8 finds that one of the 4K pages of memory one app is using is the same as the one another app is using, it only keeps one of them and shares it between them.
Initially, Windows 8 seems to be using less memory than Windows 7 on similar hardware, but we need to test this in more depth to see how it affects performance.
If you're going for something more modern, Windows 8 supports the new sector sizes on larger hard drives. It also supports a range of interesting sensors - temperature, pressure and current as well as the usual light, motion and location. It even supports specialised sensors such as blood pressure, for building health-tracking tools.
With the developer preview of Windows 8, you have to do a clean installation on your PC, and that's going to be true of the beta and any release candidate version too.
The release version of Windows 8 will be able to upgrade Windows 7 PCs. The problem for pre-release versions is that there's no way of undoing the installation, so you can't go back if anything goes wrong. It's also likely that you will have to do a clean install of each new test version of Windows 8 as they come along.
From the testing we've done so far, the developer preview of Windows 8 itself is pretty reliable, but the same isn't true of some of the Metro apps.
Initially some of these froze or showed only a blank screen. And because Metro apps get suspended automatically if you're not using them, there isn't an easy way to close an app except through Task Manager. This is finger-friendly enough, but isn't as easy as dragging the app off the top of the screen the way you can on the HP TouchPad, say.
We don't expect to see reliability problems in the long term, and Microsoft is very clear that this is a pre-beta preview version of code. We've already seen a newer build with more interface features running, so issues at this stage don't necessarily mean a black mark for the release version of Windows 8.
Our early Windows 8 verdict
Although it has previously hinted at a Windows 8 release date Microsoft isn't officially talking about a release date for x86 PCs or for new ARM devices.
We don't know anything about price, or about which different versions of Windows will be on sale.
This is a developer preview to encourage developers to start writing Metro applications, and to remind users that an iPad or Android tablet isn't the only option.
We'd say it succeeds in that. Windows 8 is on target to give you a tablet experience that's very like Windows Phone on a bigger screen, with the same fluid and responsive and very personal experience, plus the same sort of smart integration between different applications.
But you also get the desktop that's almost what you're used to, with all the applications people are still buying PCs for - at least on x86 PCs.
The Start screen is a very different way of working from the Start menu, and we're not convinced everyone will take to it. However, upcoming features such as semantic zoom may make a difference there.
The transition between the Start menu and the desktop is also a little jarring, even though switching from Metro to desktop apps works well.
It may be that Microsoft will refine the experience, or it may be that people will get used to it. At this stage there are certainly rough edges, but the Windows 8 experience is also extremely compelling and genuinely innovative.
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