Operating Systems Layer
IB Syllabus: A1.3 – Operating systems and control systems
Table of Contents
Overview
The Operating Systems Layer covers how system software manages hardware resources, provides services to applications, and creates a user-friendly interface between humans and machines. It also includes control systems – specialised computing systems that use sensors and actuators to monitor and manage real-world processes.
This layer covers all 7 outcomes of A1.3 (Operating systems and control systems). A1.3.1–A1.3.4 are assessed at both SL and HL; A1.3.5–A1.3.7 are HL only.
Sub-pages
| # | Topic | Syllabus | Key Concepts | Level |
|---|---|---|---|---|
| 1 | OS Fundamentals | A1.3.1, A1.3.2 | Role of OS, key functions (memory, file, device, security, scheduling), types of OS | SL + HL |
| 2 | Scheduling | A1.3.3 | Process states, FCFS, Round Robin, Priority, Multilevel Queue, Gantt charts | SL + HL |
| 3 | Polling and Interrupts | A1.3.4 | Polling, interrupt handling, ISR, CPU overhead, latency, real-world scenarios | SL + HL |
| 4 | Multitasking | A1.3.5 | Context switching, resource contention, deadlock, starvation, semaphores | HL only |
| 5 | Control Systems | A1.3.6, A1.3.7 | Sensors, actuators, transducers, open-loop vs closed-loop, feedback, real-world applications | HL only |
Teaching Sequence
These topics follow the classroom teaching order (W16–W22), starting with OS fundamentals after completing the Hardware Layer:
- OS Fundamentals (W16–W17) – Role, functions, and types of operating systems
- Scheduling (W17) – CPU scheduling algorithms with Gantt chart exercises
- Polling and Interrupts (W18) – How the OS detects and responds to hardware events
- Multitasking (W21, HL) – Concurrency, resource allocation, and deadlock
- Control Systems (W22, HL) – Sensors, actuators, and feedback loops in real-world systems
Learning Objectives
By the end of this topic, you should be able to:
- Describe the role of operating systems and their key functions (A1.3.1, A1.3.2)
- Compare different scheduling approaches: FCFS, Round Robin, Priority, Multilevel Queue (A1.3.3)
- Evaluate the use of polling versus interrupt handling for different scenarios (A1.3.4)
- Explain how the OS manages multitasking and resource allocation, including deadlock (HL) (A1.3.5)
- Describe the components of a control system: sensors, actuators, transducers, controllers (HL) (A1.3.6)
- Explain how control systems are used in real-world applications, distinguishing open-loop from closed-loop (HL) (A1.3.7)
Connections
- Hardware Layer – The OS manages hardware resources: CPU scheduling, memory hierarchy, device I/O (A1.1)
- Information Layer – Data representation underpins how the OS stores and processes information (A1.2)
- Programming Layer – Understanding OS concepts (memory, processes, file I/O) helps explain runtime behaviour of programs (B2, B3)
- Communication Layer – The OS manages networking, protocols, and security that enable communication (A2)
- Applications Layer – Applications run on top of the OS and rely on its services for resource access (A3)