C4/Abstraction/4 - Code

• Code (C4 abstraction)

  • Overview

    • Code elements are the programming-language building blocks that implement a C4/Abstraction/3 - Component: classes, interfaces, enums, functions, objects, and similar constructs.
    • The finest C4 static zoom; many teams skip drawing it and rely on the IDE or generated UML instead.

  • Context

    • Fourth level of C4: answers how is this component* actually built—often too detailed* for stakeholder decks but useful for developers onboarding to a module.

  • Key principles

    • Honest detail — Show the architecturally relevant types and relationships, not every POJO or util class.
    • Optional by value — If the diagram adds no new insight, omit it.

  • Mechanism

    • Expressed in C4/Diagram/4 - Code views; frequently auto-generated from source when used at all.

  • Examples

    • A UML-style class diagram for a service’s core types; a module dependency sketch in lieu of full UML.

  • Misconceptions

    • “C4 requires code diagrams” — False; context + container often suffice per C4/Diagram.
    • “Code diagram = full class diagram of everything” — Usually noise; C4 expects selective structure, not inventory.