e as follows: Software as a Service (SaaS) Application developers manage and develop specific applications for enterprises. Enterprise and residential customers pay monthly fees to use these applications, which are generally accessed via a web browser interface. Platform as a Service (PaaS) Providers make their hardware and basic application suite available to developers and enterprises that create specialized add-on applications for specific functions. Infrastructure as a Service (IaaS) Developers create applications on basic computing and storage infrastructure owned and supported by cloud providers. This is the hardware used by developers. www.TechnicalPDF.com Software as a Service is the most frequently used cloud service. Organizations that want to avoid the staff time needed to develop, test, and roll out new applications often use Software as a Service. With SaaS, new applications can be implemented more quickly than if the customer implemented them on their own servers. They can turn to developers to write them or simply use existing cloud-based applications. Customers are attracted to Software as a Service because the cloud provider manages applications, the operating systems on which applications are installed, the virtualization in the server, servers, storage, and broadband connections between users and the applications. The customer's responsibility is porting applications to the cloud, and monitoring the billing and usage. Many SaaS providers offer applications, such as Salesforce.com and NetSuite, used by business and commercial organizations. Salesforce.com offers its customer relationship management (CRM) services for managing relationships concerning customers and sales prospects. Its software can be used to automate writing sales proposals. It also profiles and targets customers based on these profiles. NetSuite, owned by Oracle, offers businesses an end-to- end software suite that includes CRM, inventory, and e- commerce applications that integrate web sales with back-office functions such as 