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OCR H446 1.2.2 Libraries, linkers and loaders

Part 5 of 7 · H446 1.2.2 · Applications generation

A library, a linker and a loader are distinguished in H446 1.2.2 by reusable code, combination at build time and placement in memory at run time. This worksheet follows compiled modules all the way to a running program, so that a build failure and a launch failure are diagnosed to the right tool.

Students will:

  • describe what a library provides and what a linker combines into a single executable
  • explain the loader's run-time role in placing code and data into main memory
  • develop several distinct benefits of using an external library beyond a one-word claim
  • state risks of depending on external library code and pair a mitigation with each
  • distinguish an unresolved-routine build failure from a failure to load at launch

Inside: 5 explanation cells, 1 multiple-choice question, 2 fill-in-the-blanks cells and 5 written answers. 51 marks, about 40 to 50 minutes.

Series: H446 1.2.2 · Applications generation, part 5 of 7.

Shared by Coding PathwayVerified teacher

  • 13 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.

Libraries, linkers and loaders

Worked model: reuse, build, run

Arrowed library, linker and loader build-run pathbuild time and run time are different momentsBUILD TIMEobject modulestranslated program partslibrary codereusable routineslinkerresolves/combinesexecutableone runnable programRUN TIMEOS loaderloads required statemain memorycode + required data/librariesLinker: executable. Loader: memory and execution.

A library supplies reusable routines. At build time the linker resolves or combines program/object modules with required library code/references to form an executable. At run time the operating-system loader places the executable and required code/data into memory.

Fill in the blanks4 marks
Reusable routines are stored in a gap 1. The gap 2 forms the executable from program/object and required library code. The operating-system gap 3 places the executable and required state into gap 4.
  • library
  • linker
  • loader
  • memory
  • compiler
Multiple choice1 mark

Which description contains the missing second linker mark that candidates often omitted?

  • AIt combines required program/library code to form one executable
  • BIt links libraries
  • CIt loads source into the compiler
  • DIt places an executing program in memory

Library decision

Benefits can include faster development/debugging, reusable tested routines, specialist/optimised implementations, portability and consistency. Drawbacks can include poor fit, dependency or version failure, security risk, licensing constraints, resource overhead and reliance on external maintenance. Pre-tested does not mean the complete program needs no testing.

Written answer8 marks

Explain four distinct benefits of using a numerical library in an environmental model. Develop each beyond a one-word claim.

Connect library property -> developer/runtime consequence. Do not repeat ‘saves time’ four ways.

Students type their answer here.

Written answer9 marks

Explain three drawbacks or risks of using an external image-processing library in a long-lived public service, and give one mitigation for each.

Use dependency, security, licence, fit, maintenance or resource angles.

Students type their answer here.

Written answer9 marks

Diagnose each failure: (1) an unresolved routine name prevents an executable being formed; (2) an executable exists but required code cannot be placed in memory at launch; (3) a library update changes behaviour. Name the responsible stage/tool and one useful check.

Separate build time, load time and runtime/dependency behaviour.

Students type their answer here.

Apply the model independently

The remaining tasks change the context or reduce the support. Complete them without copying the worked model, then check that each explanation connects a mechanism to its consequence.

Written answer8 marks

A robotics team compiles three modules and uses a tested sensor library. Explain the complete path from source modules to a running program, including compiler output, linker input/output and loader action. Conclude why the library, linker and loader cannot be treated as one interchangeable stage.

Use moments and states, not only tool names; finish with the build-time/run-time distinction.

Students type their answer here.

Written answer8 marks

Repair: ‘Libraries contain source that the loader tests, and the linker puts it into RAM, so the program no longer needs testing.’

Correct library purpose, linker, loader and testing claim.

Students type their answer here.

Fill in the blanks4 marks
A library supports code checkpoint gap 1. The linker produces an checkpoint gap 2 at build time. The loader places required code and data into checkpoint gap 3 at run time. Pre-tested routines reduce work but do not remove checkpoint gap 4.

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.