Category Archives: .net

.net, development, microsoft

Microsoft’s Scott Guthrie on what has happened to Silverlight

32 Comments

I spoke to Microsoft’s Scott Guthrie last week, during his trip to the UK for a couple of Windows Azure events in Cambridge and London.

Guthrie is now Corporate VP Windows Azure Application Platform, a job he took up in May 2011. Before that he worked on .NET technologies including Silverlight, and I asked if he had any reflections on the subject. He was scrupulously tactful.

“In terms of looking at our XAML stack right now, if you look at some of the announcements we’ve made in terms of Windows 8, Metro, Surface, tablets and desktops, and Windows Phone, XAML is alive and well and being used for more things than ever.

“Silverlight 5 shipped after I moved on to Azure. We did an update to Silverlight 5 about a month ago. For XAML developers, and developers using Silverlight or WPF XAML technologies, there is a long roadmap ahead.”

He seemed to me to be saying that even if Silverlight is dead (nobody expects a Silverlight 6), XAML lives on.

I observed that in the new (and much improved) Windows Azure admin portal, the Silverlight UI has gone, replaced by an HTML 5 user interface.

“It’s actually HTML, it’s not HTML 5. It works with non HTML 5 browsers as well.“ he said. “That was less of a technology statement, it was more that, historically Azure had 5 or 6 admin tools that were fairly disjoint. One of the decisions we made as part of the new Azure that we’re building was, let’s have a single admin tool framework that connected everything. We decided to do it with HTML, partly because we did want to get reach on tablets like iPads and Android devices.

“It was less a technology statement, it was more that we wanted a single admin tool, and we decided to go with an HTML-based approach. We still use Silverlight for some of our admin experiences like database management tools, and for streaming and other capabilities.”

It is true that Silverlight remains in the Azure database design tool, if you use the portal. It is also used extensively in System Center 2012 – yes, I have actually installed it – and in Windows InTune.

It is as if, back in 2009 and early 2010, the memo went out: use Silverlight for everything. Then, later in 2010, the memo went out: use HTML for everything; but too late for the current generation of server admin products.

Microsoft has announced that Visual Studio LightSwitch, which generates Silverlight applications, is being revised to offer HTML applications as well. I expect this process of Silverlight removal and de-emphasis to continue over the next couple of years. Note that Microsoft’s own Windows RT does not support Silverlight (as far as I am aware), nor does Windows 8 on the Metro side.

.net, microsoft, mobile, windows

Windows Phone 8 and Windows 8: nearly converged

4 Comments

Microsoft has shared details of the forthcoming Windows Phone 8 operating system, which is set to be available on devices before the end of 2012.

The improvements are fundamental, and it seems that Microsoft has finally created a mobile platform that has what it takes, technically, to compete in the modern smartphone market. Winning share from competitors is another thing of course; Nokia’s hoped-for third ecosystem is still tiny relative to Apple iOS or Google Android.

It starts with a change in the core operating system, from Windows CE to Windows 8. The two now share the same kernel, and APIs including Graphics, Audio, Media, File System, Networking, Input, Commerce, Base Types and Sensors. The .NET Framework is also the same. The browser will be Internet Explorer 10.

image

Silverlight was not mentioned, nor was XNA, though we were told that Windows Phone 7.x apps will run on Windows Phone 8.

The change does enable multi-core support at last. Screen resolution can now go up to 1280 x 768, ready for high-definition displays. There is also support for MicroSD storage, a feature which should have been in the first release.

What about Windows RT, the runtime for Metro-style apps in Windows 8? Here is the significant slide from yesterday’s presentation:

devchoices

This looks similar to Windows RT, which also supports three development models: XAML and .NET, native C/C++ code, and HTML5. It is not quite the same though. One thing I did not hear mentioned was contracts, the communication and file sharing system built into Windows 8, though we were promised “sharing under user control”. Nor did we hear about language “projections”, the layer that lets different languages in Windows 8 call the same Windows Runtime APIs. My guess at the moment is that Windows Phone 8 does not include the Windows Runtime, though it does have much in common with it. The further guess is that the full Windows Runtime will come in Windows Phone 9.

In other words, it seems that Windows Phone 8 will not run apps coded for Windows 8, though we were told that if you code to the XAML and .NET model for apps, and the native code model for games, few changes will be needed. XNA developers should consider a change of direction.

Support for C/C++ is a key feature and one that in my view should have been in the first Windows Phone release. One of the things it enables is official support for SQLite, the cross-platform database engine also found in Mac OS X and numerous other platforms. A good day for SQLite, which pleases me as I am a fan.

There will also be C/C++ gaming libraries coming to Windows Phone 8, including Havoc:

havoc

What else is new? Users will like the new Start screen, which unlike the whole of Windows Phone 8 is also coming to existing devices, which will get a half-way upgrade called Windows Phone 7.8 (7 and 8, geddit?). The innovation in the new Start screen is that any tile can be sized by the user to any of the supported sizes. The smallest size allows four tiles across, so you can make your Windows Phone look more like Android or iOS if you so choose.

newstart2

What else? Microsoft is not announcing “end-user features” yet, but did promise Nokia offline maps plus turn by turn directions; digital wallet which can be paired with a secure SIM for NFC (near field communications) payment, and deep support for Skype and VOIP so they “feel like any other call”. Apparently operators will love the way the wallet is implemented, because unlike Android it is hooked to the SIM, but I doubt they will be so keen on Skype.

There is an improved speech engine which duly failed to recognise speech input correctly in the first demo, though it worked after that.

Finally, Microsoft is now talking Enterprise for Windows Phone. There will be bitlocker encryption and enterprise app deployment without Windows store, as well as device management. Think full System Center 2012 integration.

Conclusion? There is disappointment that existing Windows Phone 7 devices are not fully upgradeable, but this is hardly surprising given the changed core. As a platform it is greatly improved, though I would like to see full WinRT included. Despite its poor start, you cannot dismiss this mobile OS as Microsoft continues to use its financial muscle to try and try again.

If it succeeds, will it be too late for Nokia? Maybe, though my hunch is that Microsoft will do what it takes to keep its key mobile partner alive.

.net, cloud computing, microsoft, mobile, windows

Three reasons why Microsoft should make its own Windows RT (ARM) Tablet

2 Comments

Rumours are flying that Microsoft will announce an own-brand Windows RT tablet on Monday.

No comment on the truth of these, but it would be a smart move.

Here are three reasons.

First, the OEM foistware problem. This has got a little better in recent years, but not enough to compete with Apple and its clean machines. The problem is so bad that Microsoft set up its own retail stores to sell  cleaned-up Windows PCs:

Many new PCs come filled with lots of trialware and sample software that slows your computer down—removing all that is a pain, so we do it for you! Every PC the Microsoft Store sells is put on a software diet and performance is tuned to run the best it can.

Microsoft addressed this in Windows Phone by imposing conditions on the extent to which OEMs can customise the user interface or embed their own software. It cannot do this  though with Windows 8 on x86. Manufacturing its own model is one of the few ways Microsoft can get Windows PCs that work as designed into the hands of consumers.

Second, the design problem. Few Windows PCs (if any) are as well designed as Macs or iPads. Manufacturers are geared towards low prices and frequent model changes rather than intensive work on every detail of the design.

Third, Microsoft wants to make a splash with Windows RT, the ARM version, and there is evidence that it is having difficulty communicating its benefits or convincing its OEM partners to get fully behind it.

This third is the biggest issue, which might drive Microsoft to compete with its third-party partners, and requires some explanation. Many people I speak to cannot see the point of Windows RT. This version of Windows 8 will not run x86 applications, so you cannot install any of your old software. Further, there is no way to install desktop applications, so software vendors cannot port their existing applications. They must create new Metro-style apps instead. So why bother with Windows RT?

This reaction is understandable, but unfortunately for Microsoft Windows 8 on x86 has no chance of competing with Apple’s iPad.

Yesterday I attended an Asus event in London where the company was showing its new range of Android tablets and Windows ultrabooks. It was not showing its prototype Windows 8 machines, but I was able to discuss the likely Windows 8 products, All but one is x86, and they will have Wacom digitizers,  which means they will work with a stylus like an old-style Tablet PC, as well as with touch. That will push up the price.

Worse still, these x86 devices, like the Samsung Slate on which I run WIndows 8 Release Preview, will not be enjoyable to use with touch alone. Users will find themselves running applications designed for keyboard and mouse: you can get them to work, but it is frustrating. These devices are not Windows reimagined, they are the old Windows plus a few new tricks.

Too expensive, too hard to use: Windows 8 on x86 is not an iPad-beater.

Windows RT on the other hand is more promising. This does have a desktop, but it will only run Office, Windows Explorer, and whatever other desktop utilities Microsoft chooses to provide. Office aside, you will be forced to use touch-friendly Metro apps most of the time. Microsoft can tune Windows RT by removing legacy components that are no longer needed, because applications which rely on them cannot be installed. You also get the power efficiency of ARM, so a long battery life. Finally, if Microsoft has done it right Windows RT should be more secure, since the entire operating system is locked down.

Windows RT is critical to Microsoft and if it has to make its own hardware in order to market it properly, then it should do so.

.net, microsoft, professional, software development, visual studio

New Windows 8, new Visual Studio 2012

Microsoft has released the Release Candidate of Visual Studio 2012 (now the official name), which you can download here, to coincide with the release of Windows 8 Release Preview and Windows Server 2012 Release Preview.

Visual Studio also has a new logo, as you can see from the setup window below.

image

Microsoft’s Jason Zander has posted about the new release here. Some of the main areas of difference between the RC and the Beta are:

  • Better performance
  • User interface tweaks including the return of a little more colour to the product
  • Solution Explorer filtering
  • New Metro style app templates
  • Improved XAML and Blend designers
  • Updated ASP.NET 4.5 web forms to support the await keyword
  • Tweaks to LightSwitch, Team Foundation Server, Architectural Tools

There is also a more detailed post by Scott Hanselman on what’s new in web development here.

.net, javascript, professional

Convert .NET Intermediate Language to JavaScript

3 Comments

Whomever called JavaScript the assembly language of the web was a true prophet.

Compiling .Net code to JavaScript is not new. I have heard that Microsoft’s Office Web Apps, browser-hosted editing of Office documents, are built with Script#.

The difference with JSIL is that it compiles .NET Intermediate Language (IL), and therefore works with any .NET language – though note that:

JSIL is still in development. You will hit bugs

The screenshot says it all

image

.net, development, mobile, silverlight, software development, visual studio, windows

Hands on: building an app for Windows 8 Metro

2 Comments

How difficult is it to build an app for the Windows Runtime (WinRT), which powers Metro-style apps in Windows 8?

Here is how I created a simple calculator app (this is one in an occasional series) using Visual Studio 11 beta. I started with a new Visual C# Windows Metro Style project, choosing a blank template.

image

A slight complication is that you are prompted to install a Developer License, which means logging into your Windows Live account.

image

Next, I had to layout the controls. Visual Studio creates a single-page app with a main page called BlankPage.xaml. I renamed this to Calc.xaml. I also used Visual Studio’s refactor menu to rename the page class from BlankPage to Calc.

image

The default application has a black background, which seems gloomy. I changed the Background of the container grid to white.

My basic calculator design is based on six rows and four columns, so I added 6 RowDefinitions and 4 ColumnDefinition to the XAML grid. The units for RowDefinitions and ColumnDefinitions can be set to Auto, Pixel or Star. Star means the unit is a weight which is calculated at runtime. For example, if you set the value of one RowDefinition.Height to 2 and the others to 1, the first one would be twice as high as the others. Here is my basic grid:

image

Next, I placed controls in the grid. The easiest way to get them to fill the space neatly is to set their HorizontalAlignment and VerticalAlignment properties to Stretch. Then you control the margin round the control with the Margin property. You can have a control fill more than one cell by using the Grid.ColumnSpan and Grid.RowSpan properties.

I found it easier to add the controls in code using copy and paste.

image

A Grid has no FontSize property, and although the Page has a FontSize property it does not seem to be inherited by the controls. I therefore set the FontSize individually for each control but there must be a better way of doing this.

I then wrote minimal code that performs calculations without always crashing, and tested the app.  When you debug, you can choose Local Machine, Simulator, or Remote Machine. I found it easier to debug using the simulator, since if you use Local Machine and Visual Studio is running on the main display, then the app you are debugging becomes invisible if you hit a breakpoint or exception. The simulator seems really good (it is actually a remote session into your own machine) and I would like some way of running all Metro apps in a window like this, not just for debugging!

image

A few reflections

A developer with experience of C# and XAML (which is also used by Windows Presentation Foundation and by Silverlight) will not have much trouble getting started with WinRT, though I noticed that XAML is substantially cut-down, as Patrick Klug observes here.

Visual Studio 2011 is an excellent IDE although I do not much like the new property editor; a minor point, but I find the latest go at prettification detrimental to usability; it is too busy. This may be a matter of familiarity and it is a minor point.

image

The XAML visual designer is slow to refresh even with my simple app, so this could be annoying with a more complex layout.

Layout with XAML works well, though it is more difficult than say Windows Forms for a new developer. It is easy to get peculiar results unless you do everything with pixel layout, which is not the best approach.

What about Metro itself? Apps always run full screen, and I had a problem with this in that my little calculator does not need all that space.

image

I am not a designer; and I suppose with a bit of effort you could add some decoration or effects to use the space, or add extra features. But why?

I was thinking about the Atari ST the other day, following the death of Jack Tramiel. The ST did not really multitask, but to get around the problem of needing to run a second app without closing the first, it had the concept of desktop accessories, available from a pull-down menu. My calculator would work well as a desktop accessory in Metro, except there is no such concept – unless you count the “Snap” split view. I wonder if Microsoft is too religious about its “Immersive UI” concept.

A few reservations then; but that does not take away from the overall impression of a strong integrated development experience for building Metro-style apps.

.net, microsoft, professional, software development, visual studio, windows

Developers: will you do Metro?

6 Comments

It is fascinating to watch the Metro-fication of all things Microsoft, from the Xbox 360 user interface to Windows Phone to Windows 8 to forthcoming versions of Office and other applications.

Future versions of Dynamics products were previewed at the Convergence 2012 event (which included a session called CRM goes Metro) and there are a bunch of screenshots here.

image

Microsoft calls Metro a design language and you can see its guiding principles here. Calling it a language does not seem quite right; the word “style” is more accurate, but it does have building block elements (and yes it is blocky) which I guess make it more than just a style.

A safe prediction at this point is that all Microsoft’s products will be touched by Metro influence, even though not all will become full Metro apps running on the Windows Runtime (WinRT).

In the past the style adopted by Microsoft for its own applications have strongly influenced third-party applications as well. Once Windows, Office, Dynamics and other apps have a Metro look, other apps that do not may begin to look dated or out of place.

Metro is controversial though, perhaps even more so than the Office Ribbon which replaced menus in Office 2007 and 2012. There is some connection: members of the Office team who worked with Steven Sinofsky on the design of Office 2007, including Julie Larson-Green and Jensen Harris, are now working with him on Windows 8. Harris has written extensively about the work on Office 2007 on his Office User Interface Blog, though the last substantial post was in 2008.

What’s not to like about Metro? Here’s a few arguments against:

  • Beauty is in the eye of etc; but the blockiness of the Metro style does give it a utilitarian appearance. In Windows Phone 7 it is nice to use, but not so great to look at.
  • The Live Tile concept, where shortcut blocks can be populated with current information, adds a random element to Metro start screens which does not always look good.
  • The emphasis on simplicity and immersion makes Metro vulnerable to the accusation that it wastes too much precious screen space.
  • Metro tends to be a horizontally scrolling style, though I am not sure if this is baked into the guidelines. This takes some adjustment since most of us are more used to vertical scrolling to see more content.
  • Metro seems to be optimized for a touch UI, and while its advocates insist that it is just as good with keyboard and mouse, that is a stretch. Metro seems to be a big bet on touch as the future of human-computer interaction.

On the other hand, the usability of Windows Phone 7 is a point in its favour, and some are convinced. Paul Greenberg, in a positive take on Microsoft’s strategy based on his trip to Convergence 2012, says:

They have nailed UX (a.k.a user experience). Nailed it. Their combination of the extremely well done Metro interface and their work on natural user interfaces involving voice and touch is the new gold standard – and I’m someone who loves Apple products. (please, Mac fanboys, spare my life.)

I would be interested to hear from developers whether you expect to embrace the Metro style in your apps, wither in WinRT or elsewhere.

.net, azure, cloud computing, microsoft, open source, software development

Microsoft’s platform nearly invisible at QCon London 2012

3 Comments

QCon London ended yesterday. It was the biggest London QCon yet, with around 1200 developers and a certain amount of room chaos, but still a friendly atmosphere and a great opportunity to catch up with developers, vendors, and industry trends.

Microsoft was near-invisible at QCon. There was a sparsely attended Azure session, mainly I would guess because QCon attendees do not see that Azure has any relevance to them. What does it offer that they cannot get from Amazon EC2, Google App Engine, Joyent or another niche provider, or from their own private clouds?

Mark Rendle at the Azure session did state that Node.js runs better on Windows (and Azure) than on Linux. However he did not have performance figure to hand. A quick search throws up these figures from Node.js inventor Ryan Dahl: 

  v 0.6.0 (Linux) v 0.6.0 (Windows)
http_simple.js /bytes/1024 6263 r/s 5823 r/s
io.js read 26.63 mB/s 26.51 mB/s
io.js write 17.40 mB/s 33.58 mB/s
startup.js 49.6 ms 52.04 ms

These figures are more “nothing to choose between them” than evidence for better performance, but since 0.6.0 was the first Windows release it is possible that it has swung in its favour since. It is a decent showing for sure, but there are other more important factors when choosing a cloud platform: cost, resiliency, services available and so on. Amazon is charging ahead; why choose Azure?

My sense is that developers presume that Azure is mainly relevant to Microsoft platform businesses hosting Microsoft platform applications; and I suspect that a detailed analysis would bear out that presumption despite the encouraging figures above. That said, Azure seems to me a solid though somewhat expensive offering and one that the company has undersold.

I have focused on Azure because QCon tends to be more about the server than the client (though there was  a good deal of mobile this year), and at enterprise scale. It beats me why Microsoft was not exhibiting there, as the attendees are an influential lot and exactly the target audience, if the company wants to move beyond its home crowd.

I heard little talk of Windows 8 and little talk of Windows Phone 7,  though Nokia sponsored some of the catering and ran a hospitality suite which unfortunately I was not able to attend.

Nor did I get to Tomas Petricek’s talk on asynchronous programming in F#, though functional programming was hot at QCon last year and I would guess he drew a bigger audience than Azure managed.

Microsoft is coming from behind in cloud -  Infrastructure as a Service and/or Platform as a Service – as well as in mobile.

I should add the company is, from what I hear, doing better with its Software as a Service cloud, Office 365; and of course I realise that there are plenty of Microsoft-platform folk who attend other events such as the company’s own BUILD, Tech Ed and so on.

Update:

This is the basis for the claim that node.js runs better on Windows:

IOCP supports Sockets, Pipes, and Regular Files.
That is, Windows has true async kernel file I/O.
(In Unix we have to fake it with a userspace thread pool.)

from Dahl’s presentation on the Node roadmap at NodeConf May 2011.

.net, development, microsoft, mobile, software development, windows

Windows on ARM: Microsoft can write Desktop apps, but you cannot

15 Comments

Microsoft’s Windows chief Steven Sinofsky has written a long post describing Windows on ARM (WOA), which he says is a:

new member of the Windows family, much like Windows Server, Windows Embedded, or Windows Phone

There are many point of interest in the post, but the one which stands out for me is that while the traditional Windows desktop exists in WOA, third party applications will not be allowed there:

Developers with existing code, whether in C, C++, C#, Visual Basic, or JavaScript, are free to incorporate that code into their apps, so long as it targets the WinRT API set for Windows services. The Windows Store can carry, distribute, and service both the ARM and x86/64 implementations of apps (should there be native code in the app requiring two distributions).

says Sinofsky. He writes with extreme care on this issue, since the position for which he argues is finely nuanced. Why have the Windows desktop on WOA at all?

Some have suggested we might remove the desktop from WOA in an effort to be pure, to break from the past, or to be more simplistic or expeditious in our approach. To us, giving up something useful that has little cost to customers was a compromise that we didn’t want to see in the evolution of PCs

he says, while also saying:

WOA (as with Windows 8 ) is designed so that customers focused on Metro style apps don’t need to spend time in the desktop.

From a developer perspective, the desktop is more than just a different Windows shell. Apps that run on the Windows Runtime (WinRT) are isolated from each other and can call only a limited set of “safe” Windows APIs, protecting users from malware and instability, but also constraining their capabilities. The desktop by contrast is the old Windows, an open operating system. On Windows 8 Intel, most things that run on Windows 7 today will still work. On WOA though, even recompilation to target the ARM architecture will not help you, since Microsoft will not let desktops apps install:

Consumers obtain all software, including device drivers, through the Windows Store and Microsoft Update or Windows Update.

What if you really want to use WOA, but have some essential desktop application without which you cannot do your work, and which cannot quickly and easily be ported to WinRT? Microsoft’s answer is that you must use Windows on Intel.

That said, Microsoft itself has this problem in the form of Office, its productivity suite. Microsoft’s answer to itself is to run it on the desktop:

Within the Windows desktop, WOA includes desktop versions of the new Microsoft Word, Excel, PowerPoint, and OneNote, codenamed “Office 15”.

No Outlook, which I take to imply that a new WinRT-based Exchange client and PIM (Personal Information Manager) is on the way – a good thing.

Microsoft’s aim is to give customers the security and stability of a locked-down machine, while still offering a full version of Office. If you think of this as something like an Apple iPad but with no-compromise document editing and creation, then it sounds compelling.

At the same time, some users may be annoyed that the solution Microsoft has adopted for its legacy desktop application suite is not also available to them.

The caveat: it is not clear in Sinofsky’s post whether there may be some exceptions, for example for corporate deployments, or for hardware vendors or mobile operators. It will also be intriguing to see how Office 15 on ARM handles extensibility, for example with Office add-ins or Visual Basic macros. I suspect they will not be supported, but if they are, then that would be a route to a kind of desktop programming on WOA.

It will be interesting to see how Microsoft locks down Explorer, which Sinofksy says is present:

You can use Windows Explorer, for example, to connect to external storage devices, transfer and manage files from a network share, or use multiple displays, and do all of this with or without an attached keyboard and mouse—your choice.

By the way, this is a picture of the Windows ARM desktop as it looked at the BUILD conference last September. The SoC (System on a Chip) on this machine is from NVIDIA.

.net, cloud computing, hardware, microsoft, mobile, windows

Windows Phone 8 “Apollo”: Windows 8 kernel, more form factors

Microsoft’s partner ecosystem is vulnerable to leaks, as demonstrated today by reports of a video said to have been made for Nokia, which arrived in the hands of a smartphone review website. The leaked information was corroborated by Windows journalist Paul Thurrott who has received advance information independently from Microsoft, but under non-disclosure:

Thanks to a recent leak which has revealed some interesting information about the next major Windows Phone version, I can now publicly discuss Windows Phone 8 for the first time.

First, a quick recap:

  • Windows Phone 7.5 “Mango” came out in the second half of last year and was the launch OS for Nokia’s Lumia phones.
  • Windows Phone “Tango” is expected in the second quarter of 2012 and appears to be a minor update focused on low-end handsets.
  • Windows Phone “Apollo” is the subject of the new leaks. Some of the details:
  • Uses the Windows 8 kernel and other OS components, rather than Windows CE
  • Supports multicore processors
  • Supports more form factors and screen resolutions
  • Preserves compatibility with Windows Phone 7 apps
  • Adds BitLocker encryption

I presume this also means that native code development will be supported, as it is for the Windows Runtime (WinRT) in Windows 8.

Date for “Apollo”? The rumour is towards the end of this year, as a close follow-on from Windows 8 itself.

Like many leaks, this one raises as many questions as it answers. While it makes sense that Windows Phone 8 and Windows 8 should share the same kernel, it also raises the question of  how they are differentiated. Windows 8, especially on ARM, is designed for small screens and tablets. Windows Phone 8, we now learn, will support more form factors. The implication is that there may be Windows Phone 8 devices that are close in size to Windows 8 devices. Will they run the same apps from the same Marketplace, at least in some cases, in the same way that some iOS apps support both iPhone and iPad?

The Windows 8 and Windows Phone 8 era will be simplified in one sense, with a single core operating system across desktop and devices. In another sense though, it ushers in new complexity, with multiple platforms that have subtle or not so subtle differences:

  • Windows 8 desktop side, on laptop and tablet (x86)
  • Windows 8 desktop side, laptop and tablet (ARM) – rumoured to be locked down for Office and perhaps a few other favoured apps
  • Windows 8 Metro side, desktop, laptop and tablet (x86) which should be nearly the same as
  • Windows 8 Metro side, desktop, laptop and tablet (ARM) – runs WinRT
  • Windows Phone 8 – runs WinRT, plus Silverlight compatibility layer

My guess is that Microsoft will push WinRT as the single platform developers should target, but I can see scope for confusion among both developers and users.