What is cloud computing and differentiate among IaaS, PaaS, and SaaS with examples.

• A. Cloud delivers IT resources over the internet; IaaS provides infrastructure (e.g., AWS EC2), PaaS provides a platform (e.g., Heroku), SaaS provides applications (e.g., Office 365).
• B. Cloud delivers only storage, not compute.
• C. IaaS provides applications; PaaS provides hardware; SaaS provides platforms.
• D. Cloud services require on-premises servers.

Answer: (D)

Cloud computing means delivering computing resources over the internet on a pay‑as‑you‑go basis, instead of owning and managing your own hardware. In IaaS you rent the basic building blocks—virtual machines, storage, and networking—and you install and manage the operating system, runtime, and applications yourself. The provider takes care of the physical infrastructure and virtualization. A common example is AWS EC2 or Google Compute Engine, where you control the VM and the software you run on it. In PaaS the provider supplies a ready-to-use platform with the runtime, middleware, database support, and deployment tools, so you focus on writing and deploying your application while the platform handles the underlying environment and scalability. Examples include Heroku, Google App Engine, and AWS Elastic Beanstalk. In SaaS you access fully functional software hosted by the provider over the internet; you use the application directly, with the provider handling everything from the infrastructure to the software updates. Examples are Microsoft 365, Google Workspace, and Salesforce. The main trade-off is control versus convenience: more control and responsibility in IaaS, less in PaaS, and minimal management in SaaS. Clouds are about delivering compute, storage, and services via the internet, not just storage, and you don’t need on‑premises servers for these models.