Cloud computing is a phrase used to describe a variety of computing concepts that involve a large number of computers 1 through a real-time communication network such as the Internet.In science,cloud computing is a 2 f or distributed computing over a netwrok,and means the 3 to run a program or app lication on many connected computers at the same time. The architecture of a cloud is developed at three layers: infrastucture,platform,and application,The infrastructure layer is built with virtualized compute,storage,and network resources .The platform layer is for general-purpose and repeated usage of the collection of software resources.The application layer is formed with a collection of all needed software modules for SaaS applications.The infoastructure layer serves as the 4 for building the plarform layer of the cloud. In turn,the platform layer is a foundation for implementing the 5 layer for SaaS applicationgs.