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With the success of SaaS-based solutions, few desktop solutions are built today. Instead, developers create applications to run within the cloud and on mobile devices. Behind the scenes, developers who create new cloud-based applications or who move existing applications to the cloud are truly driving the cloud’s explosive growth. Creating a cloud-based application is very similar to building a traditional web-based application. Developers normally use a programing language such as PHP, Ruby, Perl, Python, or C#, along with HTML and CSS, and a database. Many cloud-solution providers offer tools that developers need to build and deploy a solution, as discussed in Chapter 3, “Platform as a Service (PaaS).”