This page covers how wiRedPanda saves and loads circuits, exports to hardware description languages, visualizes waveforms, and manages resources and translations.

---

## The `.panda` File Format

Circuit files (`.panda`) use a binary format (`App/IO/Serialization.h`):

```
[Preamble]
  - Magic number (0x57504346 = "WPCF") + format version
  - Metadata (QMap): dolphin data, rect, etc.

[Elements]
  - Element count
  - For each element:
    - Type (ElementType)
    - Position, rotation, flip state
    - Input and output ports with IDs
    - Element-specific properties (frequency, color, etc.)

[Connections]
  - Connection count
  - For each connection:
    - Source port ID (output)
    - Destination port ID (input)
```

On load, a **port map** is built during element deserialization so that connections can resolve their endpoints. The format is backward-compatible and can read files from older wiRedPanda versions.

### Version History

The file `App/IO/VersionInfo.h` tracks all format versions:

| Version | Release | Key Changes                                       |
|---------|---------|---------------------------------------------------|
| V_1_1   | 2015    | Clock element added                               |
| V_2_4   | 2019    | Audio element support (Buzzer, AudioBox)          |
| V_3_1   | 2021    | Lock state for input elements; display colors     |
| V_4_1   | 2024    | QMap-based format; port serial IDs                |
| V_4_2   | 2024    | TruthTable output data stored in file             |
| V_4_5   | 2025    | Preamble gains a metadata QMap                    |
| V_4_6   | 2025    | Preamble unified into a single metadata QMap (dolphin filename and scene rect folded in) |
| V_4_7   | 2026    | QNEConnection uses QMap-based serialization       |
| V_5_0   | 2026    | File format version bump for 5.0.0                |

The deserialization code reads the file version and applies automatic migrations as needed. Reading older versions is **always** supported.

---

## Code Generation (App/CodeGen)

### Arduino (`App/CodeGen/ArduinoCodeGen.cpp`)

Converts a circuit into an Arduino sketch:
- Maps circuit inputs/outputs to GPIO pins.
- Emits `setup()` with `pinMode()` calls.
- Emits `computeLogic()` with boolean expressions for combinational logic and state machines for sequential elements.
- Supports multiple board configurations (Uno, Mega, etc.).
- Generates testbench for validation.
- Supports IC hierarchy.

### SystemVerilog (`App/CodeGen/SystemVerilogCodeGen.cpp`)

Converts a circuit into synthesizable SystemVerilog:
- Emits `module` declarations with `input`/`output` ports.
- Generates `assign` statements for combinational logic.
- Handles hierarchical IC modules recursively.
- Supports sequential elements (flip-flops).
- Can be validated with iverilog, yosys, and verilator.

---

## BeWavedDolphin (Waveform Viewer)

The built-in waveform viewer (`App/BeWavedDolphin/`) provides signal visualization, similar to GTKWave:

- **`BeWavedDolphin.cpp`**: main tool window
- **`BeWavedDolphinUI.cpp`**: generated UI layout
- **`WaveformView.cpp`**: waveform rendering
- **`SignalModel.cpp`**: data model with input and output signals
- **`SignalDelegate.cpp`**: item delegate for signal cells
- **`Serializer.cpp`**: saves/loads waveform captures

**Features:**
- **Table-based**: Rows = signals, Columns = time steps.
- **Simulation**: Runs the circuit for every input combination (or user-specified patterns).
- **Visualization**: Renders waveforms as line plots or binary values.
- **Export**: PDF, PNG, and text formats.
- **Interactive**: Users can edit input patterns, set clock waves, and zoom.

Access it from the **Simulation** menu → **Waveform** (Ctrl+W) to see how signals propagate through a circuit over time. Ideal for analyzing sequential circuits.

---

## Resources and Internationalization

### Element Icons

Icons live in `App/Resources/Components/`, organized by category:
- `Input/`, `Logic/`, `Memory/`, `Output/`, `Misc/`
- SVG format for scalability

### Translations

wiRedPanda supports 39 languages:

- `.ts` files (Qt Linguist) in `App/Resources/Translations/`
- Managed via [Weblate](https://hosted.weblate.org/projects/wiredpanda/wiredpanda)
- Compiled to `.qm` during build
- Uses `tr()` and `QT_TR_NOOP()` in code

To add a new translatable string:
```cpp
QString msg = tr("New translatable message");
```

For more details on contributing translations, see the [Translation Guide](How-to-translate.md).

---

## See Also

- [Architecture Overview](Architecture-Overview.md) — Where I/O and code generation fit in the overall architecture
- [Element System](Element-System.md) — The elements that are serialized and exported
- [Testing and CI](Testing-and-CI.md) — Tests for serialization and code generation