This document provides an architectural overview of cloud computing and describes how a payroll processing application could be migrated to the cloud. It discusses the key attributes and layers of cloud computing including infrastructure as a service (IaaS), platform as a service (PaaS), and software as a service (SaaS). It then describes how the existing payroll application, which is installed at over 300 locations, could be deployed as a multi-tenant SaaS application in the cloud to reduce costs and maintenance burdens. The document outlines how the application's components would map to a SaaS architecture and how new tenants could be provisioned.