The shape of the lesson
By the end of the lesson, learners can
- What the OS does: Learn the nine functions in the syllabus, and for each one be ready to say what the OS actually does.
- From power on to app: An application cannot talk to the hardware directly.
- Spot the function: Exam questions often describe something happening and ask which OS function it is.
- Nine functions: files, interrupts, interface, peripherals and drivers, memory, multitasking, platform for applications, security, user accounts.
- Add detail: say what the OS does for each function, not just its name.
- Layers: application on OS, OS on firmware, firmware (bootloader) on hardware.
- Bootloader: firmware in ROM that loads the OS into RAM at start-up.
One picture every idea returns to
The operating system (OS) manages the computer's hardware and software and provides a platform for running applications. Its functions are: managing files, handling interrupts, providing an interface, managing peripherals and drivers, managing memory, managing multitasking, providing a platform for applications, providing system security and managing user accounts. Applications run on the OS, the OS is run on the firmware, and the firmware (the bootloader) runs on the hardware.
Forty-five minutes, phase by phase
| Time | Phase | What happens in the room | Grouping |
|---|---|---|---|
| 0 to 5 min | Hook: predict | Open with the question in the title, The computer's manager.. The operating system sits between your apps and the hardware, sharing out memory, the processor and devices, and keeping everything secure. Put the figure on the board: it is the one picture every idea in the lesson returns to. | Whole class, then pairs |
| 5 to 13 min | Teach and check: What the OS does | Learn the nine functions in the syllabus, and for each one be ready to say what the OS actually does. | Whole class, then pairs |
| 13 to 21 min | Teach and check: From power on to app | An application cannot talk to the hardware directly. Model the worked example Start-up order on the board, one line at a time. | Pairs |
| 21 to 30 min | Teach and check: Spot the function | Exam questions often describe something happening and ask which OS function it is. Model the worked example Match the function on the board, one line at a time. Your turn: A user drags a document into a folder called Homework. Which OS function is this? | Connect-Extend-Challenge |
| 30 to 36 min | Check | The four Stage 1 questions from the student lesson, answered on mini whiteboards or by show of fingers. Re-teach the one most get wrong. | Individual, then whole class |
| 36 to 43 min | Plenary | The exam-style questions from Stage 2, one at a time: thirty seconds alone, then a random call. The feedback lines in the key give the examiner's wording. | Individual, random call |
| 43 to 45 min | Exit and homework | Set the worksheet below (6 questions, 16 marks). Learners self-assess against the objectives before they leave. | Individual |
Protect the parts that carry the learning
The sequence carries about fifty minutes of material, so the lab is driven by one student while the class predicts rather than explored freely. Times are a guide.
Protected: the check at 30 minutes. It is the only individual read on whether the key idea landed, and it is not cut.
Cut first if the build overruns: the last check in Spot the function, never the check or the plenary.
In a 60 minute block: run worksheet questions 1 to 3 in class as a Rally Coach set and model both the hardest worked example and its check live.
Connect-Extend-Challenge
After the new idea, each student writes three lines: how it connects to what they knew, how it extends their thinking, and what still challenges them. Pairs compare, then the challenges become the plenary.
The full structure, with its variations and the other twelve, is on the cooperative-learning page.
What to head off, and how
| Trap learners fall into | Teaching move that pre-empts it |
|---|---|
| "It manages memory" on its own often scores nothing. | Add the detail: it allocates memory to each program and stops programs overwriting each other's memory. |
| The bootloader is firmware, not the operating system. | The OS is usually stored on the SSD or hard disk, not in ROM. |
The operating system, firmware and the hardware: worksheet
6 questions, 16 marks. Written in the style of the papers; no past paper question is reproduced.
Identify four functions of an operating system.
Describe how an operating system manages memory.
Describe what is meant by multitasking and how the OS manages it.
Explain how hardware, firmware and an operating system are needed to run application software.
A school's computers are used by many different students. Identify three ways the operating system could help keep each student's work secure.
A student says: "The bootloader and the operating system are the same thing." Explain why the student is wrong.
Answer key and marking notes
- Managing files.
- Managing memory.
- Managing multitasking.
- Providing an interface. (Also accept: handling interrupts, managing peripherals and drivers, providing a platform for running applications, providing system security, managing user accounts; one mark each, up to four.)
- It allocates memory (RAM) to programs and data when they are loaded, and frees it when they close.
- It keeps the memory of each program separate so one program cannot overwrite another's data.
- Multitasking is running more than one program so that they appear to run at the same time.
- The OS shares processor time (and memory) between the programs, switching rapidly between them.
- The bootloader is firmware, stored in ROM, which is run on the hardware when the computer is switched on.
- The bootloader loads the operating system into RAM, so the OS is run on the firmware.
- Applications are run on the operating system, which provides them with services such as memory and access to hardware.
- Separate user accounts with a username and password for each student.
- Access rights so a student can only open their own files.
- A firewall and automatic security updates (or locking the screen after inactivity).
- The bootloader is firmware stored in ROM that runs first when the computer is switched on.
- Its job is to load the operating system, which is usually stored in secondary storage and then runs from RAM.
6 multiple-choice questions on this lesson
From the topic question bank. Assign them in the app for a marked score in your gradebook, or run the topic as a class game.
Which operating system function shares processor time between several programs so they appear to run at the same time?
- AManaging multitasking
- BHandling interrupts
- CManaging files
- DProviding an interface
A user saves an essay, renames it Final and moves it into a folder called English. Which operating system function is being used?
- AManaging files
- BManaging memory
- CManaging user accounts
- DManaging peripherals and drivers
Where is the bootloader stored?
- AIn non-volatile memory such as ROM
- BOn the hard disk with the operating system
- CIn RAM, so it can be changed by the user
- DIn the processor's cache
A student opens a game while a large download continues. The OS gives the game its own section of RAM and stops it overwriting the download's data. Which function is this?
- AManaging memory
- BManaging multitasking
- CProviding system security
- DProviding a platform for running applications
Which sequence correctly describes what happens from switching on a computer to running a word processor?
- AThe hardware runs the bootloader; the bootloader loads the OS into RAM; the OS loads the word processor
- BThe OS loads the bootloader; the bootloader loads the hardware; the word processor starts the OS
- CThe word processor runs on the firmware; the firmware loads the OS; the OS starts the hardware
- DThe bootloader loads the word processor from ROM; the word processor then loads the OS
An exam asks students to describe how an operating system manages memory. Which answer would earn the marks?
- AIt allocates RAM to each program when it loads, frees it when the program closes and keeps programs' memory separate
- BIt manages the memory so that the computer works properly
- CIt makes the RAM bigger when it becomes full so more programs can run
- DIt stores every program permanently in RAM so they load faster
Quiz key
Managing multitasking means the OS switches the processor rapidly between programs, so they seem to run together. Handling interrupts deals with signals that need attention, managing files organises stored data, and the interface lets the user communicate with the computer.
Saving, naming and moving files into folders (directories) is managing files. Managing memory allocates RAM to running programs, managing user accounts keeps each user's files and settings separate, and managing peripherals uses drivers to communicate with devices.
The bootloader is firmware held permanently in non-volatile memory (ROM), so it can run at power on. The operating system, not the bootloader, is usually on the hard disk or SSD. RAM and cache are volatile and are empty when the computer starts.
Allocating RAM to each program and stopping programs overwriting each other's memory is managing memory. Multitasking is sharing processor time. System security covers logins, firewalls and access rights. Providing a platform is the general idea of giving applications services, but the specific function described here is memory management.
At power on the hardware runs the bootloader (firmware in ROM). The bootloader loads the operating system from storage into RAM. The OS then loads applications and provides their services. The other sequences reverse the layers: the OS does not load the bootloader, applications do not run directly on firmware, and the word processor is not stored in ROM.
The creditworthy answer gives the detail: allocating RAM, freeing it, and stopping programs overwriting each other's memory. Simply repeating "manages the memory" adds nothing. The OS cannot increase the physical size of RAM, and RAM is volatile, so programs are not stored there permanently.
Slides for this lesson
A projectable deck for every pack is on the way. Until then, present the student lesson full screen: its sections, figure and lab tabs follow the same order as the plan above.