IAAS ,SAAS, and PAAS --> Windows Azure.

Infrastructure as a Service (IAAS)

Vendors provide the infrastructure to build solutions, and you rent the hardware such as servers, load balancers, a firewall, and cables. You then configure these remotely and install your solutions on them. You can scale up by requesting more servers and reconfiguring the load balancer without purchasing more hardware. You can scale down at any time by reconfiguring the infrastructure you rented from the cloud service provider. This vendor approach is called Infrastructure as a Service (IaaS) because a customer can rent the infrastructure without having to forecast and provision for the highest possible demand in advance. In this approach, you are responsible for correctly configuring the rented infrastructure.

Software as a Service (SAAS)

In another approach, you can rent a service offered by the vendor and then configure the service by using the interface provided by the vendor, without having to know what infrastructure the vendor uses to provide that service. This approach is called Software as a Service (SaaS) because you pay to use defined services. For example, Microsoft Exchange Online carries a per-mailbox charge. To configure it, you use a web application supplied by the vendor to request mailboxes, and name and dimension them. You receive a password for that user and nothing else is necessary—users can access their mailboxes immediately.

Platform as a Service (PASS)

The third approach is Platform as a Service, or PaaS. In this approach, you rent a platform on which you deploy your applications without configuring the infrastructure and without the limitations of the SaaS approach.

The Windows Azure platform fits best in the PaaS category, because it doesn’t provide access to the underlying virtualization environment or operating system details such as the network interface, IP configuration, and disk management.

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Windows Azure Step By Step -->

What is Windows Azure ?

Windows Azure is an operating system, which is created for cloud computing. Like all operating systems, its purpose is to provide an abstraction from the physical hardware components and a set of services that every application can use.
In other words, Windows Azure has the same role as a traditional operating system on any hardware platform.

It also has many similarities to—as well as many differences from—a traditional file system. Unlike a traditional operating system such as Windows 7, which abstracts a single box with its CPU, hard disks, keyboard, mouse, and graphics cards, Windows Azure abstracts a set of servers, providing a common platform for building services and applications in a completely virtual environment. In this environment, you work with servers, but you do not install the application on server A or server B; you deploy an application, but not on a specific disk C or D; and you do not have to configure the network card or the virtual directory to expose your services.

Like traditional operating systems, Windows Azure exposes a way to store data, called local storage. However, this storage doesn’t consist of physical hard disks nor is it a traditional network share such as \\servername\sharename. Instead, Windows Azure provides shared storage. It provides CPU power—but not just the processors you can see when you open the case of a physical server. In fact, no one can see the actual disks or machines that host a Windows Azure solution; you just upload the application to the environment and let Windows Azure choose the best servers, disks, and load balancing strategies for a particular solution. You can describe your application’s needs in a logical way. For example, you can request 1 GB of local disk space to cache remote resources, but you cannot force Windows Azure to deploy your solution on a specific disk or server. You can specify that your application needs to listen for HTTPS requests on port 443, but you cannot configure the IP address of the virtual node.

Windows Azure you cannot install on locally, there is no installer available. 

How to connect with Azure world ?

Open your browser and type address  [www.windowsazure.com]

Click on Free Trial

Sign in with Microsoft account /Hotmail account or create new -->

Enter your Credit card details (Dont worry your data and card is safe with Microsoft - Note deduct 1.0 $ from your credit card).

After Setting up of your Windows Azure subscription, you have to open [manage.windowsazure.com] for managing your Azure.
Now you can start managing your Windows Azure.

With Windows Azure you can configure WebSite, Create Virtual Machines as per your requirement, you can start Mobile services , cloud services SQL database, Use Storage, the best thing you can create and manage your Active directory from here.

Ok, next i am going to sharing about IAAS, SAAS and PAAS.

Thanks comments awaited.

Enjoy on Microsoft Cloud.