billing and accounts receivable. Young people and adults as well use SaaS applications in their personal lives. For example, students in particular back up their music on sites such as iTunes. The following is a quote from a Chinese exchange student in the Boston area: I use the cloud to back up my music. I like being able to listen to my music from all of my www.TechnicalPDF.com devices. And, I don't have to worry about running out of space on my smartphone. Services for residential customers, such as the Office- like Google Docs suite, the document-sharing service DropBox, the backup service Carbonite, and social media sites LinkedIn and Facebook are examples of Software as a Service. PaaS: Cloud-Based Data Centers with Specialized Software Platform as a Service providers manage the operating system, servers, virtualization, storage, and networking within their data centers. They provide data centers with specialized software to enterprises and application developers. For example, one PaaS provider, Microsoft, currently maintains massive data centers in the United States, Europe, and Asia. The Microsoft Azure platform is available to developers to customize applications that they in turn offer to their customers. Both Salesforce.com and NetSuite sell directly to developers as well as to business customers. The services Salesforce.com and NetSuite sell to developers are considered PaaS offerings because developers use the platforms to customize and support software for their own customers. An enterprise customer can also create applications directly on Azure, or use standard office software such as word processing and spreadsheet applications as well as productivity applications such as web conferencing and calendaring, and then later port them to Azure. By using applications housed on Azure, organizations eliminate the complexity of supporting in-house applications. Azure also offers storage facilities to developers and enterprise customers. A bank can store a year's worth of records on Azure to which each of i