# DOS_Sim

**Repository Path**: eran/dos_sim

## Basic Information

- **Project Name**: DOS_Sim
- **Description**: DOS
- **Primary Language**: Unknown
- **License**: GPL-2.0
- **Default Branch**: master
- **Homepage**: None
- **GVP Project**: No

## Statistics

- **Stars**: 0
- **Forks**: 0
- **Created**: 2026-10-07
- **Last Updated**: 2026-10-07

## Categories & Tags

**Categories**: Uncategorized

**Tags**: None

## README

# DOS Simulator

A DOS emulator for iOS and iPadOS, built on the DOSBox 0.74-3 core with a
SwiftUI front end.

This repository contains the complete corresponding source code, as required
by the GPLv2 license the core is derived from.

## Requirements

- macOS with Xcode (Apple Silicon or Intel)
- iOS 26.5 or later for the app target (`NativeDosCore` itself targets 15.0)

## Build

```bash
cd XCode/DOS_Simulator
open DOS_Simulator.xcodeproj
```

Select the `DOS_Simulator` scheme and run. The `NativeDosCore` target builds
the emulator core as a static library and is built automatically as a
dependency of the app.

To build from the command line:

```bash
# Core only
xcodebuild -project DOS_Simulator.xcodeproj -scheme NativeDosCore \
  -configuration Debug -sdk iphoneos build

# Full app
xcodebuild -project DOS_Simulator.xcodeproj -scheme DOS_Simulator \
  -configuration Debug -sdk iphoneos \
  -destination 'generic/platform=iOS' build
```

The app bundles the core, which is a fat static library carrying both
`arm64` (device) and `x86_64` (simulator) slices, so a simulator build must
keep `ONLY_ACTIVE_ARCH=NO`.

### Regenerating the core target

`XCode/DOS_Simulator/Tools/generate_core_target.rb` recreates the
`NativeDosCore` target and re-adds the third-party sources to the build. It is
idempotent, so it can be re-run safely. It needs the `xcodeproj` gem:

```bash
cd XCode/DOS_Simulator
ruby Tools/generate_core_target.rb
```

## Running DOS games

The app's `Documents` directory is mounted as drive C:. Put the game files
directly in `Documents` (not in a subfolder), then either type the program
name at the DOS prompt or add it to the `[autoexec]` section of
`Documents/config/dospad.cfg`:

```ini
[autoexec]
PLAY.BAT
```

Configuration is read from `Documents/config/dospad.cfg`. The app writes a
default one on first launch if it is missing.

Note that the DOSBox shell does not accept relative paths with a drive letter
(`C:\PLAY.BAT` reports `Illegal command`); either `cd` first or use the bare
file name.

No game content is included in this repository.

## Known limitations

- **Pause is a spin poll.** The main loop checks the pause flag every 0.25s,
  so resuming from the background can lag by up to that much.
- **The core cannot be stopped.** SDL 1.2 offers no way to terminate the
  DOSBox main loop from outside, so "stop" degrades to a `reboot` back to the
  prompt. A full restart requires restarting the app process.
- **Command injection is a hack.** Queued commands are pushed by sending a
  Return to interrupt the shell's readline. It is timing sensitive.
- **The DOS `OPEN` command is not implemented.**
- **SDL 1.2 is end of life.** Xcode updates may require patches.
- **On-screen controls are not wired up yet.** The current UI only starts the
  core and reports its state.

## License

GPLv2. See [LICENSE](LICENSE).

The core is derived from [iDOS](https://github.com/litchie/dospad) by litchie,
which is GPLv2, so the whole application is distributed under GPLv2.

### Third-party components

| Component | Version | License | Location |
|---|---|---|---|
| DOSBox | 0.74-3 | GPLv2 | `NativeDosCore/dosbox` |
| iDOS (dospad) | as vendored | GPLv2 | `NativeDosCore/dosbox` (iOS-specific changes) |
| SDL | 1.3.0 (hg-4429) | LGPLv2.1 | `NativeDosCore/SDL`, `NativeDosCore/include` |
| SDL_sound | as vendored | LGPLv2.1 | `NativeDosCore/SDL_sound` |
| SDL_net | as vendored | LGPLv2.1 | `NativeDosCore/SDL_net` |
| mt32emu | as vendored | LGPLv2.1 | `NativeDosCore/mt32emu` |
| libFLAC | prebuilt | LGPLv2.1 | `NativeDosCore/deps/lib` |
| libogg | prebuilt | BSD | `NativeDosCore/deps/lib` |
| libvorbis / libvorbisenc / libvorbisfile | prebuilt | BSD | `NativeDosCore/deps/lib` |
| libmpg123 / libout123 / libsyn123 | prebuilt | LGPLv2.1 | `NativeDosCore/deps/lib` |

`NativeDosCore/deps/lib` contains prebuilt static libraries inherited from
iDOS. Their sources are available from the upstream projects listed above.

This project also uses zlib and the iOS system frameworks.