---
title: DOSLIB
url: 'https://wiki.teletypegames.org/dos/doslib'
markdown: 'https://wiki.teletypegames.org/dos/doslib.md'
lang: en
date: '2026-10-11'
description: 'DOSLIB is the code that the DOS programs DOSINST, GMENU, BMAGIC and TTGWIKI share (C++, Open Watcom, 16-bit DOS and Win32), and the rules their code follows. Each program has it in its SOURCE/lib folder as a git subtree, so it builds on its own. Repository: git.teletypegames.org/dos/doslib What…'
taxonomy:
  tag:
    - howto
---

# DOSLIB

> DOSLIB is the code that the DOS programs [DOSINST](https://wiki.teletypegames.org/dos/dosinst), [GMENU](https://wiki.teletypegames.org/dos/gmenu), [BMAGIC](https://wiki.teletypegames.org/dos/bmagic) and [TTGWIKI](https://wiki.teletypegames.org/dos/ttgwiki) share (C++, Open Watcom, 16-bit DOS and Win32), and the rules their code follows. Each program has it in its `SOURCE/lib` folder as a git subtree, so it builds on its own.

- **Repository:** [git.teletypegames.org/dos/doslib](https://git.teletypegames.org/dos/doslib)

# What is in it

| Folder | What |
|---|---|
| `core` | No I/O: strings and 8.3 names, INI files, UTF-8 and code page 437, the code pages 437 and 852 with one byte a character (`code_page`), CRC-32, the shared `Error`. |
| `platform` | The interfaces of the machine: `Screen`, `Keyboard`, `Mouse`, `Clock`, `FileSystem`, `Network`, ... |
| `platform/dos`, `platform/win32` | Their implementations: video memory, BIOS, INT 33h, the Watcom C library; the Win32 console. |
| `net` | An FTP client on the `Network` interface. |
| `ui` | Drawing on a `Screen`, the BIOS key codes, a list cursor. |
| `testing` | The hooks of the test builds (scripted keys, screen dump), and test doubles for the unit tests on the host. |
| `tools` | The Watcom build helper, the layer check, the unit test runner, the formatter. |

# Layers

A program is built in layers; each uses only the ones below it, and only through their interfaces:

```
main_*.cpp     the machine: picks the platform implementations
app/           puts the layers together
controller/    keys and commands -> service calls
view/          draws
service/       what the program does
repository/    interfaces of the storage; repository/<kind>/ implements them
model/         the data and its rules, no I/O
platform/      the program's own machine interfaces and their implementations
lib/           DOSLIB
```

`tools/check_layers.py` checks it in CI: which folder may include which, that the DOS and Windows headers are only in the platform code, no `goto`, no `exit()` outside `main`. Everything above the platform also compiles on the host, so it is unit tested there, without DOSBox.

# The code

- C++98, the part Open Watcom compiles: classes, pure virtual interfaces, references, simple templates; no exceptions, RTTI, STL or C++11.
- Interfaces are named by what they are (`FileSystem`), implementations by how (`DosFileSystem`, `FakeFileSystem`). Dependencies come in through the constructor; only `app/` and `main_*.cpp` create concrete objects.
- Failures are a `bool` and a shared `Error`; no global state outside the platform code.
- Files `snake_case`, types `PascalCase`, functions `camelCase`, members `name_`; clang-format 18 with the repository's `.clang-format`.

# Updating a program

```sh
git subtree pull --prefix=SOURCE/lib ssh://git@git.teletypegames.org:2222/dos/doslib master --squash
```

A change made in a program's `SOURCE/lib` goes back with `git subtree push --prefix=SOURCE/lib ... master`.

# Open Watcom notes

- The 16-bit compiler of the large model crashes on a module name longer than 25 characters; the build cuts it with `-nm`.
- A static object over 32 KB ends up in the EXE file: big objects are allocated on the heap.
- On 16 bits the layers cost size (far pointers, constructors, virtual tables): GMENU grew from 30 to 45 KB, DOSINST from 77 to 90 KB.

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---

## Navigation

- Parent: [DOS](https://wiki.teletypegames.org/dos.md)
- Previous: [DOSINST](https://wiki.teletypegames.org/dos/dosinst.md)
- Next: [GMENU](https://wiki.teletypegames.org/dos/gmenu.md)