# Chapter 1: Boot Sequence

## Sample code

- Directory: `docs/os-on-arduino/code/01_boot`

```bash
uv run pio run -d 01_boot -t upload
uv run pio device monitor -b 115200
```

## Source code

The sketch for this chapter. Click a file name to expand. The code is mirrored automatically from the manuscript repository, so what you see here is always current.

### `docs/os-on-arduino/code/01_boot`

:::{dropdown} `src/main.cpp` — 63 lines
:icon: code

[Open on GitHub](https://github.com/iory/learning-os-from-arduino/blob/main/docs/os-on-arduino/code/01_boot/src/main.cpp)

```{literalinclude} ../../../../code/01_boot/src/main.cpp
:language: cpp
:linenos:
```

:::

### `docs/os-on-arduino/code/01_boot_vector_dump`

:::{dropdown} `src/main.cpp` — 60 lines
:icon: code

[Open on GitHub](https://github.com/iory/learning-os-from-arduino/blob/main/docs/os-on-arduino/code/01_boot_vector_dump/src/main.cpp)

```{literalinclude} ../../../../code/01_boot_vector_dump/src/main.cpp
:language: cpp
:linenos:
```

:::


## On the board

```{figure} ../_static/ch01_boot.gif
:name: fig-ch01-boot
:width: 100%

Nothing appears for a while after the monitor opens; everything comes out at once the moment you send `S`. If `data_var` reads `12345`, copying the initialized data worked.
```

## Pitfalls

(Collected from reader questions — ask via
[GitHub Issues](https://github.com/iory/build-your-own-arduino-rtos/issues).)