AQA 7517 4.6.1.4: Role of an operating system (OS)
The free BugBot lessons that teach this point, a robot to try it on, and the past-paper questions that test it.
What it covers
At GCSE (F9.9) you listed what an operating system does: the user interface, memory management, multitasking, peripherals, users and files. At A level the question is why it is organised that way. The answer is two ideas: the operating system hides the complexity of the hardware, and it manages resources that many programs compete for. This lesson covers both, then the two pieces of low-level software that make them possible: the BIOS, which starts the machine, and device drivers, which let the operating system talk to hardware it has never seen.
- Hiding the hardware
- Managing resources
- Device drivers
- The BIOS and booting
Or do it in the simulator, with tasks that mark themselves
Lessons that teach it
- A10.2 The operating system, BIOS and device drivers Operating systems, software and translators
Hiding the hardware, managing resources, booting from the BIOS, and a driver table for the robot. - A10.3 Memory management: paging, segmentation and virtual memory Operating systems, software and translators
Logical and physical addresses, page tables, segments, page faults and disk thrashing. - A10.4 Interrupts Operating systems, software and translators
Polling versus interrupts, priorities, the stack and interrupt service routines in the fetch-decode-execute cycle. - A10.5 Scheduling algorithms Operating systems, software and translators
First come first served, round robin, shortest job first, shortest remaining time and multi-level feedback queues, compared on one set of… - A10.9 Project: a tiny robot operating system Operating systems, software and translators
Share the robot between three tasks with round robin, drive it through device drivers, and stop the patrol with an interrupt.
Try it on a robot
The task from A10.2 The operating system, BIOS and device drivers, running here. Change the program and press Run.
The specification is AQA's own document; this page says which of our lessons teach point 4.6.1.4 and is not endorsed by the board.