• "What's New in Visual Studio 2013 RC (see also directly linked MS articles)"
  Published by Microsoft
  http://msdn.microsoft.com/en-us/library/vstudio/bb386063(v=vs.120).aspx

Following release of the revolutionary Win8.1 preview, we need some special apps and features. So for that purpose Microsoft also released Microsoft Visual Studio 2013.

Some Key Features of Visual Studio 2013

Visual Studio Languages

• .NET FrameWork 4.5.1 : Now, when you compile an app that targets the .NET Framework 4.5.1, you can add binding redirects to the app configuration file if your app or its components reference multiple versions of the same assembly.
• Visual C++: New features include compiler and STL support for these features:

1. Default template arguments for function templates
2. Delegating constructors
3. Explicit conversion operators
4. Initializer lists/uniform initialization
5. Raw string literals
6. Variadic templates

JavaScript

Block Scoped Variables

You can use the new let and const keywords to declare variables for which the scope is limited to the block in which they're declared. See let Statement (JavaScript) and const Statement (JavaScript).

Container Object

You can create a collection of unique objects by using the Set Object (JavaScript) object, and you can create a collection of key/value pairs by using Map Object (JavaScript) or WeakMap Object (JavaScript).

Your App Store and Visual Studio 2013

Here you can look at the improvements in Windows 8. The main point here is the Start Button in the Taskbar. Another point is the App Store, it has many updated apps. The Windows user experience continues to evolve, and it's getting easier to develop, test, and submit apps to the Windows Store.

The developer samples are here: Windows 8.1 app samples

Microsoft launched some new APIs and features for developers.

App packaging

New app bundles make app submissions even simpler than before. Resource packs let you offer extras, like localization or assets for high-resolution displays, to users who want them, without affecting disk space, bandwidth, or the app-purchase experience for those who don't.

• Resource packs
• App bundles
• Package identity
• App bundle deployment

Asynchronous Programming

A new scheduler API lets you set the priority of tasks and manage jobs. This helps you write apps that use system resources more efficiently and provide a more responsive experience to users.

•      New WinJS scheduling module

Controls (HTML5 and JavaScript)

Add new features, like custom commands and enhanced navigation support, by using the new HTML and JavaScript controls. And updates to existing controls make them simpler to use and add features, like drag-and-drop operations. These new and updated controls make it easier than ever to create a full-featured app.

• AppBarCommand
• BackButton
• Hub
• ItemContainer
• NavBar
• WebView
• Dispose API
• ListView updates
• Repeater
• Template and binding updates

Controls (XAML with C# or C++) Add new features, like date and time pickers and enhanced navigation support, by using the new XAML controls. And updates to existing controls make them simpler to use and more versatile. These new and updated controls make it easier than ever to create a full-featured app.

• AppBar controls
• Flyout
• MenuFlyout
• FlipView updates
• CommandBar
• Hub
• SettingsFlyout
• Header support
• DatePicker
• Hyperlink
• TimePicker
• PlaceholderText

Devices

With Windows 8.1 Preview, create an app that's ready to connect to a wide range of wired and wireless devices. Your users can then enjoy the mobility and flexibility of Windows 8 devices when they view or create content, at home or on the job.

• USB
• Bluetooth
• Point of Service (POS)
• Human interface devices (HID)

DirectX programming

Windows 8.1 Preview introduces DirectX 11.2, that brings a host of new features to improve performance in your games and graphics apps.

• Dynamic shader linking
• Frame buffer scaling
• GPU overlay support
• DirectX tiled resources
• Direct3D low-latency swap chain present
• Function linking graph support
• DXGI Trim API and map default buffer
• Multithreading with SafeImageSource
• Composition of XAML visuals
• Direct2D batching with SafeImageSource

Files

Develop an app that can easily access user content, and make its own content easier for other apps to discover. You can do this in Windows 8.1 with the enhanced support for in-app file management, a wider selection of user libraries for your app to use, and the ability to push your app's unique content to the Windows Index.

• File picker updates
• File comparison
• New KnownFolders
• Manage user libraries
• Retrieve parent files or folders
• New file "Open with" option
• Add to the Windows Index
• Try method for file retrieval

Multimedia

Now it's easier to help users both create and play back exciting media experiences. Windows 8.1 Preview offers new ways to capture and process media, a simple way to add playback controls to apps that use XAML, and native support for Encrypted Media Extensions (EME) for HTML5 playback.

• Video processing
• MediaElement updates
• New media-capture features
• Play To updates
• HTML5 playback DRM support

Networking

Use simpler implementation of HTTP for all supported languages, easier communication for your app, and new APIs for location-based mobile scenarios to develop versatile connected apps.

• New HTTP Client API
• Background transfer updates
• HTTP Request filters
• Real-time connectivity
• Connected Standby updates
• Geofence support
• Wi-Fi Direct

Security

Provide users a security experience that doesn't feel like a hassle, and keep pace with the latest authentication techniques. We've got new ways to authenticate and manage users, expanded support for signatures and certificates, and new capabilities for stored credentials.

• Fingerprint authentication
• Credential Locker updates
• Windows To Go updates
• Certificate trust management
• Web Auth Broker updates
• App account settings
• Selective Wipe
• Smartcards and virtual smartcards

Store

Publish, sell, and maintain your app more easily, with commerce support for in-app purchases, new tools for managing your app's offers and tracking its performance, and a number of enhancements to the Windows Store user experience.

• App onboarding updates
• In-app commerce support
• Large in-app purchase catalog support
• Bing powered Store search
• New and improved Store pages
• Automatic app updates
• Proxy authentication for enterprise scenarios
• Redeemable credit for Store purchases

Tools

Windows 8.1 Preview also has many updates to the tools and templates that you can use to create Windows Store apps. These improvements can help cut down the work in your development and test cycles.

• General updates
• C++ development
• App Network Analyzer
• Diagnostics
• HTML design tools
• Windows App Certification Kit 3.0
• JavaScript editor
• XAML design tools

UX/UI

New windowing modes provide users more control over how they use your app. New tile features let you do more with your app's tile. And updates to search, share, and charms create a more consistent general experience for users.

• New windowing modes
• Search updates
• Charms work on every screen
• Share updates
• Tile updates
• Text to speech
• Work item scheduling with CoreDispatcher