Cloud Computing

IB Syllabus: A1.1.9 – Cloud computing service models, A1.3.2 – Virtualization

Key Concepts
Worked Examples
1. Example 1: Classify Cloud Services
2. Example 2: Recommend a Cloud Model
Quick Code Check
Spot the Error
Fill in the Blanks
Predict the Output
Practice Exercises
1. Core
2. Extension
3. Challenge
Connections

Key Concepts

What is Cloud Computing? (A1.1.9)

Cloud computing is the delivery of computing resources – servers, storage, databases, networking, and software – over the internet (“the cloud”). Instead of buying and maintaining physical hardware, organisations rent resources from a cloud provider and pay only for what they use.

Key characteristics of cloud computing:

Resources are hosted in large data centres managed by cloud providers (e.g., AWS, Microsoft Azure, Google Cloud Platform)
Pay-as-you-go pricing model – no large upfront hardware investment
Resources can be scaled up or down on demand (e.g., add more servers during busy periods)
Accessed from anywhere with an internet connection

Cloud Service Models (A1.1.9)

Cloud services are categorised into three models based on how much the provider manages versus how much the user controls.

SaaS (Software as a Service)

Complete applications delivered via a web browser
The provider manages everything: infrastructure, platform, and application
The user simply uses the software – no installation, updates, or server management
Examples: Google Docs, Microsoft 365, Canva, Gmail, Zoom
Least control, most convenience

PaaS (Platform as a Service)

A platform for building and deploying applications
The provider manages the infrastructure and runtime environment
The developer writes and deploys code without managing servers or operating systems
Examples: Heroku, GitHub Pages, Azure App Service, Google App Engine
Medium control

IaaS (Infrastructure as a Service)

Raw computing resources: virtual machines, storage, networking
The provider manages the physical hardware only
The user manages the operating system, runtime, and applications
Examples: AWS EC2, Azure Virtual Machines, Google Compute Engine, DigitalOcean
Most control, most responsibility

Control vs Responsibility Spectrum

        Least Control                        Most Control
        Most Managed                         Least Managed
        ┌──────────┬──────────┬──────────┐
        │   SaaS   │   PaaS   │   IaaS   │
        └──────────┴──────────┴──────────┘
You manage: Nothing   App code   OS + Apps
Provider:   Everything Platform   Hardware

A common exam mistake is confusing the three models. Remember: SaaS = you use it, PaaS = you code on it, IaaS = you build everything on it. The more letters before “aaS,” the more you manage.

Virtualization (A1.3.2)

Virtualization is the process of creating virtual versions of physical resources – servers, storage, or networks – using software. It is the foundational technology that makes cloud computing possible.

Hypervisor

Software that creates and manages virtual machines
Sits between the physical hardware and the virtual machines
Examples: VMware ESXi, Microsoft Hyper-V, KVM
Type 1 (bare-metal): runs directly on hardware – used in data centres
Type 2 (hosted): runs on top of an existing OS – used on desktops (e.g., VirtualBox)

Virtual Machines (VMs)

Emulate complete computer systems, each with their own operating system
Multiple VMs can run on a single physical server, each isolated from the others
One physical server might run 10 VMs, each appearing to be a separate computer

Containers

A lightweight alternative to VMs (e.g., Docker)
Share the host operating system kernel instead of running a full OS per instance
Faster to start, use less memory, but offer less isolation than VMs

Virtualization enables cloud computing because one physical server can run many virtual servers for different customers, maximising hardware utilisation.

Benefits of virtualization:

Better resource utilisation – no idle hardware; one machine serves many users
Isolation – if one VM crashes, others are unaffected
Easy scaling – spin up new VMs in minutes rather than purchasing new hardware
Snapshot and backup – save the exact state of a VM and restore it later

Cloud vs On-Premise

Factor	Cloud	On-Premise
Cost	Operational (monthly fees)	Capital (upfront purchase)
Scaling	Easy – add resources on demand	Difficult – buy new hardware
Maintenance	Provider handles updates and repairs	In-house IT team required
Control	Less – provider’s rules and configurations	Full control over all aspects
Accessibility	Anywhere with internet	Local network only (without VPN)
Security	Shared responsibility with provider	Entirely your responsibility

Enrichment: 5 Essential Characteristics (NIST)

This goes beyond the IB syllabus but helps build understanding.

The US National Institute of Standards and Technology (NIST) defines five essential characteristics of cloud computing:

On-demand self-service – provision resources (e.g., new servers, storage) without requiring human interaction with the provider
Broad network access – accessible from any device (laptop, phone, tablet) over the network
Resource pooling – the provider’s computing resources serve multiple customers simultaneously, with resources dynamically assigned based on demand
Rapid elasticity – scale up or down quickly based on demand; resources appear unlimited to the user
Measured service – usage is monitored, controlled, and billed accordingly (like a utility such as electricity)

Worked Examples

Example 1: Classify Cloud Services

For each service, identify whether it is SaaS, PaaS, or IaaS, and explain why.

Service	Model	Reasoning
Google Docs	SaaS	A complete application accessed through a browser; Google manages everything
AWS EC2	IaaS	Provides virtual machines; the user installs and manages the OS and applications
Heroku	PaaS	Developers deploy code without managing servers; Heroku handles infrastructure
Microsoft 365	SaaS	Complete productivity suite delivered via browser; Microsoft manages everything
Azure Virtual Machines	IaaS	Provides raw VMs; the user manages OS, runtime, and applications
GitHub Pages	PaaS	Developers push code and the platform builds and hosts the website automatically

The pattern: ask “who manages the operating system?” If the provider manages everything including the application, it is SaaS. If the provider manages infrastructure but you deploy your code, it is PaaS. If you manage the OS and everything above it, it is IaaS.

For each organisation, recommend the most appropriate cloud service model and justify the choice.

Scenario A: A school wants email and documents for staff and students.

Recommendation: SaaS (e.g., Google Workspace, Microsoft 365)
The school does not need to manage servers or write custom software. They need ready-made tools that work immediately. SaaS provides this with minimal IT overhead.

Scenario B: A startup is building a web application and wants to focus on writing code.

Recommendation: PaaS (e.g., Heroku, Google App Engine)
The developers want to deploy their application without managing servers, configuring operating systems, or handling scaling. PaaS abstracts away infrastructure so the team can focus on product development.

Scenario C: A large enterprise with strict regulatory compliance requirements needs full control over security configurations.

Recommendation: IaaS (e.g., AWS EC2, Azure VMs)
The enterprise needs to configure firewalls, encryption, and access controls precisely. IaaS gives them full control over the virtual machines and networking while still avoiding the cost of purchasing physical hardware.

Quick Code Check

Q1. Which cloud service model gives the user the most control over the computing environment?

Q2. Google Docs is an example of which cloud service model?

Q3. What technology enables one physical server to run multiple virtual servers simultaneously?

Q4. A developer wants to deploy a web application without managing any servers or operating systems. Which model is most appropriate?

Spot the Error

A student classified several cloud services for their exam revision. One service is classified incorrectly. Click the line with the error, then pick the correct fix.

1Google Docs → SaaS (complete application in a browser) 2AWS EC2 → PaaS (virtual machines in the cloud) 3GitHub Pages → PaaS (deploy code, platform builds the site) 4Canva → SaaS (design tool accessed via browser)

Pick the correct classification for AWS EC2:

Fill in the Blanks

Complete the comparison of cloud service models and virtualization concepts by filling in each blank.

Fill in the blanks to complete this summary of cloud computing:

CLOUD SERVICE MODELS
====================
 provides complete applications accessed through a web browser.
 provides a platform for developers to build and deploy applications.
 provides raw computing resources like virtual machines and storage.

VIRTUALIZATION
==============
A  is software that creates and manages virtual machines.
 are lightweight alternatives to VMs that share the host
operating system kernel.

Predict the Output

A small business wants to use spreadsheets, email, and document editing without managing any servers or installing software on their computers. Which cloud service model is most appropriate?

Type the service model abbreviation:

A hospital needs to host patient records in the cloud but must comply with strict data protection regulations. They need full control over firewall rules, encryption, and access policies. Which cloud service model should they choose?