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OCR H446 1.2.1 Virtual machines

Part 10 of 12 · H446 1.2.1 · Systems software

OCR uses virtual machine broadly, so H446 1.2.1 covers two quite different things under one name: software presenting a computer so a guest operating system can run inside a host, and software that executes intermediate code. This worksheet keeps them apart and evaluates virtualisation on isolation, resources and portability.

Students will:

  • distinguish a virtual machine hosting a guest operating system from one running intermediate code
  • explain how several virtual servers can run on one physical server
  • explain why the same intermediate code can be distributed to different processor types
  • weigh benefits and drawbacks of running guest operating systems in virtual machines
  • choose the right virtual concept by asking which function is being replaced

Inside: 6 explanation cells, 4 multiple-choice questions, 3 fill-in-the-blanks cells and 5 written answers. 41 marks, about 45 to 60 minutes.

Series: H446 1.2.1 · Systems software, part 10 of 12.

Shared by Coding PathwayVerified teacher

  • 18 cells
  • About 45 minutes
  • CC BY-SA 4.0
  • Shared 31 Aug 2026
  • Updated 3 Sept 2026

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The whole resource, exactly as a class sees it. Answers and marking are held back.

Virtual machines

OCR uses virtual machine broadly: software takes on the function of a machine. You must understand two important instances.

  1. Software presents a virtual computer so a guest operating system can run within a host system.
  2. A software virtual machine executes intermediate code, translating it for the target hardware.

Virtual machines are not virtual memory or virtual storage.

Worked model: two abstraction levels

Two OCR meanings of virtual machineoperating system within anotherguest OS and applicationsvirtualisation softwarehost OS and hardwareexecuting intermediate codeportable intermediate codesoftware virtual machinemachine-specific instructionsIn both cases software takes on a machine function, but the purpose and abstraction level differ.

In an OS virtual machine, the guest behaves as though it has its own processor, memory, storage and devices. Virtualisation software maps these virtual resources onto the physical host. Several isolated guests can share one machine.

In an intermediate-code virtual machine, source code is translated once into a portable intermediate representation. A suitable VM on each target converts or executes that representation for the local processor. This supports portability.

Choose the virtual concept from its job

Do not begin with the word virtual and guess. Ask what function is being replaced:

  • storage presented through a remote or abstracted location is virtual storage;
  • secondary storage supplementing limited RAM is virtual memory;
  • software behaving like a computer or executing intermediate code is a virtual machine.

In an extended response, define only the concept used by the scenario, then connect its mechanism to the supplied workload, resources and risks. Generic cloud-security claims do not replace contextual reasoning.

Multiple choice1 mark

Which definition best matches OCR's broad use of virtual machine?

  • AA physical RAM chip reserved for one application
  • BA remote folder only
  • CSoftware used to take on the function of a machine
  • DA scheduling queue stored in ROM
Fill in the blanks4 marks
In operating-system virtualisation, the physical computer is the entry 1. The operating system running inside the virtual computer is the entry 2 OS. Virtualisation software allocates virtual processor, memory, storage and entry 3 resources while keeping guests entry 4 from one another.
Multiple choice1 mark

What is one benefit of isolating a test operating system inside a virtual machine?

  • AThe VM makes the physical machine unnecessary
  • BEvery program runs with zero overhead
  • CThe VM permanently adds physical processor cores
  • DA failure or malware experiment can be contained and the VM can be reset without directly altering the host
Written answer4 marks

Explain how a company can run several virtual servers on one physical server.

Describe virtual hardware, resource sharing and one consequence.

Students type their answer here.

Worked model: intermediate code and portability

A source program is translated into intermediate code rather than directly into one processor's machine code. The same intermediate code can be distributed to several platforms. Each platform has its own compatible software VM, which translates or executes the intermediate instructions for that machine.

The program gains portability, but the target needs the VM and translation introduces processing overhead.

Fill in the blanks5 marks
Source code is first translated into entry 1 code. A platform-specific virtual entry 2 then converts or executes it as local entry 3 code. The same intermediate form can therefore run on several entry 4, improving software entry 5.
Multiple choice1 mark

Why can intermediate code be portable?

  • AA compatible VM on each target handles the translation to that target's machine instructions
  • BIntermediate code is identical to every processor's native code
  • CIt removes the need for any target software
  • DIt is stored only in virtual memory
Written answer8 marks

Explain two benefits and two drawbacks of running guest operating systems in virtual machines.

Develop each point with a mechanism or consequence.

Students type their answer here.

Multiple choice1 mark

A computer moves a page from RAM to secondary storage because RAM is full. Which concept is this?

  • AOperating-system virtual machine
  • BVirtual memory
  • CIntermediate-code virtual machine
  • DDevice-driver translation
Written answer4 marks

A developer must test an application on three operating systems without buying three computers. Explain how virtual machines help and identify one limitation of the approach.

Apply host/guest language to the scenario.

Students type their answer here.

Written answer3 marks

A language distributes the same intermediate program to laptops with different processors. Explain the role of the virtual machine on each laptop.

Follow the representation from intermediate code to execution.

Students type their answer here.

Written answer6 marks

A school plans to host several isolated training servers as virtual machines on one powerful physical server. Assess the approach and reach a justified conclusion.

Discuss resource use, isolation, management and failure/performance risk in this scenario.

Students type their answer here.

Closed-book checkpoint

Complete the common principle and the distinction between the two forms.

Fill in the blanks3 marks
Virtualisation replaces a physical function with a software entry 1. One form presents an entire computer environment to another operating system; the other processes a portable representation for a target entry 2. Both depend on underlying real resources, so allocation and translation can add entry 3.

Review your understanding

Before submitting, check that you can explain the main distinction in your own words, apply it in an unfamiliar context and justify each consequence rather than only naming a feature.