Erlang modules and the BEAM runtime

What you will learn

• Explain erlang modules in Erlang using the correct mental model
• Trace a focused Erlang example and predict its result before execution
• Recognize a boundary case involving the beam runtime and handle it deliberately

The concept

Erlang modules and the BEAM runtime is a defining part of practical Erlang work. Start by identifying the data or state involved, then trace the operation that changes or interprets it. Pay attention to the rules Erlang applies at this boundary, because those rules explain both the useful behavior and the common failure modes. This lesson keeps the example deliberately small, then connects it to expressions, clauses, and pattern syntax so the ideas form a coherent progression rather than a list of isolated syntax facts.

Example

This example is intentionally small so you can trace every line before adapting it.

-module(main).
-export([start/0]).
start() -> io:format("Hello from Erlang~n").

Read it step by step

1. 1
   Locate the idea

   Identify where erlang modules appears in the Erlang example and name the data it operates on.

2. 2
   Trace the rule

   Trace the relevant Erlang rule one operation at a time, recording any state, type, or control-flow change.

3. 3
   Test a boundary

   Change one input or boundary condition, predict the result, and compare that prediction with the documented outcome.

Common mistakes

Try it yourself