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playground-workflow

Playground workflow

Last reviewed Jun 1, 2026 Content v20260601
Track mode
server_compiled
Means
Compiled runner
Reading
~2 min
Level
beginner

This lesson

This lesson teaches Playground workflow: the syntax, patterns, and safety habits you need before advancing in C.

Coroutines replace callback hell on Android and in Ktor—structured concurrency is interview-critical.

You will apply Playground workflow in contexts like: Kernels, drivers, embedded devices, and performance libraries used by other languages.

Write C in main.c with int main(), click Run on server—the dev runner compiles with cc/gcc -std=c11 and runs the binary; read stderr for compile and linker errors (LEARNING_RUNNER_ENABLED=true). Also include stdio.h and use printf for output; keep a single main() entry point.

At the start of the track—complete before lessons that assume you understand the compiled playground.

Get the most from each lesson's compiled editor—the same habits transfer to VS Code, gdb, and CI running gcc -Wall -Wextra.

Recommended workflow

  1. Read the concept section before editing code.
  2. Click Run to compile with gcc and execute.
  3. Use printf with format specifiers (%d, %s, %p) for debug output.
  4. Fix warnings immediately—they often signal real bugs in C.

What the runner can and cannot do

  • Can — single-file main.c with standard headers
  • Needs local setup — multi-file Make projects, cross-compilers, hardware GPIO

Review JavaScript, Java, and Rust for comparison context.

Self-check

  1. What function prints to stdout in C lessons?
  2. What flag enables common warnings with gcc?

Challenge

First compile and run

  1. Click Run with the default code.
  2. Confirm output appears in the terminal.
  3. Add a second printf with your name.

Done when: the terminal shows the default message and your custom line.

Challenge

Verify compile output

  1. Run the default program.
  2. Confirm output in the terminal.
  3. Add a deliberate unused variable and observe -Wall.
  4. Fix and run again.

Done when: you see compiler warnings when appropriate and clean output after fixing.

Interview prep

What compiler flags should beginners enable?

-std=c11 -Wall at minimum; add -Wextra and -g locally for deeper diagnostics and debugging.

Interview tip Lesson completion confidence

Can you explain this lesson in 30 seconds without reading notes?

Not saved yet.

Playground

Runs on the configured server runner (dev: npm run runner with LEARNING_RUNNER_ENABLED=true). Output appears below the editor.

Check yourself

Multiple choice — immediate feedback.

Discussion

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Starter discussion topics

  • gcc error read how?
  • main signature?

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