CLOUD AND DISTRIBUTED COMPUTING
Cloud computing is the result of the evolution and adoption of existing technologies and paradigms. The goal of cloud computing is to allow users to take beneﬁt from all of these technologies. The "cloud" aims to cut costs, and helps the users focus on their core business instead of being impeded by IT obstacles.
New concepts are mixed with new ones, and some old technologies are being reinvented. Today, many research areas and projects under the cloud umbrella need to be sorted and classified. Accordingly, this survey article presents a unified view of the Cloud Computing main concepts, characteristics, models and architectures.