Yesterday Terry showed you how Windows 10 will usher in a new generation of Windows by powering innovation and more personal computing across the largest range of devices, including Microsoft Surface Hub and the world’s first holographic computing platform; Microsoft HoloLens.

Windows 10 will empower people to do some amazing things with a new version of Cortana for the PC, a new web browsing experience (“Project Spartan”), a true Xbox quality gaming experience on Windows, new holographic and group computing devices, and of course a new set of universal apps – People & Messaging, Photo, Video, Music and Maps – that begin to showcase a few of the new developer platform capabilities.

Windows 10 is also designed to be a service that delivers continuous innovation and new possibilities to the 1.5 billion people already using Windows each month. We’ll start by offering Windows 10 as a FREE upgrade to qualified Windows 7, Windows 8, Windows 8.1 and Windows Phone 8 and 8.1 customers – creating the broadest possible customer base*.

Today we’re going to talk about what it all means for you, our Windows developers.

Last April at Build 2014 we talked about the principles behind the design of our Windows development platform

In Windows 10, we are further simplifying how we talk about these goals as follows:

Driving scale through reach across device type. We are working to make Windows 10 a unified, developer platform for ALL of our devices so you can reach the greatest number of customers with your work across phones, tablets, PCs, Xbox, IoT devices and the new Surface Hub and HoloLens opportunities

Delivering unique experiences. Microsoft’s company-wide emphasis on the people using technology rather than simply the platforms themselves means that we are increasing efforts to provide new technologies that improve the way people interact with computers. With Windows 10, developers will be able to build on top of our investments in Cortana and speech recognition, touch, audio, video and holograms to extend their app experiences in ways they used to only dream about but are now possible on Windows 10.

Maximizing developer investments. We remain committed to helping you get the most out of your investments in training, tools, and code to continue and target our new offerings. We also recognize that many of you are looking for more ways to target a range of platforms with the same basic code or toolset with cross platform technologies.

Driving scale

Everyone wants a broader customer base and we believe Windows 10 will continue to increase customer adoption. Another closely related problem facing software developers today is the proliferation of device types and the amount of work it takes to consistently deliver compelling experiences across them all. Windows 10 addresses these fragmentation challenges.

First, as noted earlier Windows 10 will begin a new relationship with customers in which experiences are updated and delivered regularly – like a service, ensuring the vast majority of customers are using the latest version to take full advantage of your latest experiences. That process begins with a free upgrade for eligible Windows customers. With this new low friction and rapid cadence, Windows will empower developers to take advantage of new features and capabilities faster than ever before because now their customers are always running the latest Windows.

We’re also doing the work necessary to help make sure that apps and games look great across a full range of devices, display surfaces and input models. The Windows 10 platform will build upon the universal Windows app framework released with Windows 8.1 to provide developers the tools to deliver new app experiences across devices with a minimum amount of additional work.

Delivering unique experiences

Windows 10 introduces several new features that open up new avenues for developer innovation. With Windows 10 and HoloLens developers will have access to a platform that bridges the digital and physical world changing the way people interact with devices and applications. Many of you already tap into Cortana on phones. Soon, you’ll be able to take advantage of Cortana with new capabilities on a wider variety of Windows 10 devices.

We’ve also begun to share more about a new web experience for Windows 10 dubbed “Project Spartan,” which gives people new and better ways to engage the content they love across devices. Spartan introduces a new rendering engine designed for interoperability with the modern web. You can find out more about what Spartan means for web development from the team that built it on the IEBlog.

Maximizing your investments

Microsoft has a long history of protecting the investments of developers. For every release we dedicate an enormous number of resources to make sure the vast majority of existing applications continue to run as expected.

But protecting investments is about more than just ensuring that existing code continues to run; it’s also about safeguarding the skills you’ve spent years perfecting continue to serve you well in building solutions for the Windows 10 platform. With Windows 10 you’ll continue to build apps with the language of your choice in Visual Studio and enjoy a variety of cloud services through Azure, all of which can be developed and deployed in Visual Studio using the tools, languages and frameworks with which you are familiar.

Maximizing investments also speaks to our promise to support cross platform solutions. We know that developers have made investments in order to more easily target multiple platforms and device types. Accordingly, we’ve taken steps to make it easier than ever for developers working across platforms to also bring their solutions to Windows.

Back at Build last year we announced that we were releasing Win JS for use under an open source license across platform. (http://dev.windows.com/en-us/develop/winjs and http://try.winjs.com). We continue to invest in improving these libraries, with the release of Win JS 3.0 last September, a major update.

We then announced plans to help developers use Visual Studio and C# to deliver solutions to iOS and Android (as well as Windows), leveraging tools like Xamarin (http://xamarin.com) and Unity (http://unity3d.com). We also recently announced support for applications built using Apache Cordova in Visual Studio, with a full Android emulator experience (). Finally, for native C++ developers, we recently announced Visual Studio support for building not only shared libraries for Android, but also complete Native Activity applications for Android.

What’s next?

We’re more committed than ever to making sure that you can leverage your work to reach more customers, regardless of where they are, what device type they’re on, or what operating system they’re running. The best way to start preparing for Windows 10 is to start building universal Windows apps today for Windows 8.1.

Here are some great resources to get started:

Official Documentation

Comprehensive Online Training

Developing Universal Windows Apps (C#/XAML) Jumpstart. On demand training providing real world guidance to build universal Windows apps with C# and XAML.

If you are currently a Windows Phone Silverlight developer, there’s never been a better time to investigate moving your development over to Windows XAML, which provides the ability to deliver universal Windows apps. We recently released a comprehensive set of materials detailing how. Check them out here.

We’ll have much more to share about the Windows 10 developer experience over the coming months. Build 2015 will be full of detailed Windows 10 platform information. Registration opens today, so hurry to secure a seat by visiting buildwindows.com [Update: Build is currently sold out but we encourage you to join the wait list]. You can read more about Build from Steven Guggenheimer here.

We know many of you will participate in the Windows Insider Program , through which you will be able to acquire the latest builds of Windows 10. Keep in mind that this is prerelease software, and you are likely to encounter a variety of issues at this stage. You will likely not want to use this yet as your primary development Operating system.

We’re also working to include our developer tools and SDKs into the Windows Insider Program in the future, so if you want to be one of the first ones to receive early previews of our tools please sign up today.

*Hardware and software requirements apply. No additional charge. Feature availability may vary by device. Some editions excluded. More details at http://www.windows.com.