The Windows Azure Platform is Microsoft’s Windows Platform as a Service (PaaS) offering that runs on servers and
related network infrastructure located in Microsoft data centers and is connected to the public Internet. The
platform consists of a highly scalable (elastic) cloud operating system, data storage fabric and related services
delivered by physical or logical (virtualized) Windows Server 2008 instances. The Windows Azure Software Development
Kit (SDK) provides a development version of the cloud-based services, as well as the tools and APIs needed to develop,
deploy, and manage scalable services in Windows Azure, including Visual Studio 2008 or 2010 templates for a standardized
set of Azure applications.

According to Microsoft, the primary uses for Azure are to

Add web service capabilities to existing packaged applications

Build, modify, and distribute applications to the Web with minimal on-premises resources

Perform services, such as large-volume storage, batch processing, intense or high-volume computations, and so on, off premises

Create, test, debug, and distribute web services quickly and inexpensively

Reduce costs and risks of building and extending on-premises resources

Reduce the effort and costs of IT management

The economic environment into which Microsoft released Azure in late October 2008 dictates that cost reduction — mentioned repeatedly in the preceding list — will be the primary motive for its adoption by small, medium, and enterprise-scale IT departments.

Microsoft designed the Azure Platform to enable .NET developers to leverage their experience with creating in Visual Studio 2008+ ASP.NET Web applications and Windows Communication Framework (WCF) services. Web application projects run in a sand-boxed version of Internet Information Services (IIS) 7; file-system-based web site projects aren’t supported, but announcement of a “durable drive” is expected at PDC 2009. Web application and Web-based services run in partial trust Code Access Security, which corresponds approximately to ASP.NET’s medium trust and limits access to some OS resources. The Windows Azure SDK (March 2009 CTP) enabled optional full trust Code Access security for invoking non-.NET code, using .NET libraries that require full trust, and inter-process communication using named pipes. Microsoft promises support for executing Ruby, PHP, and Python code in the cloud platform. The initial development platform release was restricted to Visual Studio 2008+ as the development environment with future support scheduled for Eclipse tools. The Azure Platform supports Web standards and protocols including SOAP, HTTP, XML, Atom, and AtomPub.