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OCR H446 1.2.1 Paging and segmentation
Part 2 of 12 · H446 1.2.1 · Systems software
Paging and segmentation both divide memory, and H446 1.2.1 answers lose marks by blurring them. This worksheet fixes the distinction on four points: how the division is made, where the parts are placed in RAM, how they are mapped back to the program, and which kind of fragmentation follows.
Students will:
- distinguish equal fixed-size pages from variable-size logical segments
- read a page table to explain why storage order need not match program order
- separate internal from external fragmentation and state the cause of each
- recommend paging or segmentation for a described program and acknowledge one limitation
- explain how controlled memory allocation protects one process from another
Inside: 6 explanation cells, 5 multiple-choice questions, 3 fill-in-the-blanks cells and 3 written answers. 28 marks, about 40 to 50 minutes.
Series: H446 1.2.1 · Systems software, part 2 of 12.
Shared by Coding PathwayVerified teacher
- 17 cells
- About 45 minutes
- CC BY-SA 4.0
- Shared 31 Aug 2026
- Updated 3 Sept 2026
Preview
The whole resource, exactly as a class sees it. Answers and marking are held back.
Paging and segmentation
The operating system must allocate RAM to several programs and keep track of where their instructions and data are stored. Dividing memory into smaller sections makes allocation more flexible.
This worksheet compares two methods: paging and segmentation.
You should already know: RAM holds programs and data that are currently in use.
Worked model: two ways to choose boundaries
Paging divides a program and memory into equal fixed-size units. The boundary is chosen by size, not by what the code means. Pages belonging to one program can occupy non-adjacent locations, and a page table records their locations.
Segmentation divides a program into logical sections such as code, data or a stack. Segments can have different sizes because each complete section has a different length.
Which feature identifies paging rather than segmentation?
- AEvery division represents a complete logical section
- BEvery division has the same fixed size
- CEvery program must occupy one continuous block
- DEvery division is stored permanently on disk
| Feature | Paging | Segmentation |
|---|---|---|
| Size | entry 1 | entry 2 |
| Basis | entry 3 division | entry 4 division |
| Boundary follows program meaning? | entry 5 | entry 6 |
A compiler's instructions, program data and call stack are placed in different variable-sized sections. Which method is being described?
- APaging
- BRound robin
- CSegmentation
- DVirtualisation
Worked model: location does not have to match order
A four-page program has this page table:
| Page | RAM location |
|---|---|
| 0 | 5 |
| 1 | 2 |
| 2 | 8 |
| 3 | 1 |
The program's pages are numbered in program order, but they are stored in free locations 5, 2, 8 and 1. The table provides the mapping needed to find each page. The pages do not need to sit next to one another.
What is one benefit of allowing pages to occupy non-adjacent free locations?
- AEvery page is guaranteed to remain in cache
- BPage tables are no longer needed
- CSecondary storage becomes as fast as RAM
- DA program can use separated free areas rather than requiring one large continuous block
Compare paging and segmentation.
Give at least two paired differences using the same comparison criteria.
Students type their answer here.
Why free space can still be awkward
Internal fragmentation is unused space inside an allocated fixed-size page because the program does not fill the final page completely.
External fragmentation is free memory split into separate gaps between allocated variable-size sections. The total free space may be large enough, but no individual gap may fit the next segment.
These terms deepen the comparison and appeared in OCR assessment guidance, but the core distinction remains fixed pages versus variable logical segments.
A segment needs 40 MB. Free gaps of 15 MB, 20 MB and 25 MB exist, but none is large enough on its own. What problem is illustrated?
- AExternal fragmentation
- BInternal fragmentation
- CA page-table lookup
- DA processor interrupt
A program contains a large data section and several much smaller logical modules. Recommend paging or segmentation for preserving meaningful program sections, and justify the choice while acknowledging one limitation.
Make the criterion in the question central to the recommendation.
Students type their answer here.
A student says, ‘Paging keeps each complete function together because page boundaries are logical.’ What is the best correction?
- ACorrect, paging and segmentation are identical
- BPaging uses fixed-size boundaries that may split logical sections; segmentation follows logical sections
- CPaging uses variable-size boundaries and segmentation uses fixed-size boundaries
- DNeither method divides a program
Explain how controlled memory allocation can help protect one process from another.
Link allocation to restricted access and a consequence.
Students type their answer here.
Closed-book checkpoint
Retrieve the allocation model without looking back. There is no answer bank.
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.