# Introduction

This page attempts to explain the basic information you need to know to work with the QMK project. It assumes that you are familiar with navigating a Unix shell, but does not assume you are familiar with C or with compiling using make.

## Basic QMK structure

QMK is a fork of [Jun Wako](https://github.com/tmk)'s [tmk_keyboard](https://github.com/tmk/tmk_keyboard) project. The original TMK code, with modifications, can be found in the `tmk` folder. The QMK additions to the project may be found in the `quantum` folder. Keyboard projects may be found in the `handwired` and `keyboard` folders.

### Keyboard project structure

Within the folder `keyboards` and its subfolder `handwired` is a directory for each keyboard project, for example `qmk_firmware/keyboards/clueboard`. Within it you'll find the following structure:

* `keymaps/`: Different keymaps that can be built
* `rules.mk`: The file that sets the default "make" options. Do not edit this file directly, instead use a keymap specific `Makefile`
* `config.h`: The file that sets the default compile time options. Do not edit this file directly, instead use a keymap specific `config.h`.

### Keymap structure

In every keymap folder, the following files may be found. Only `keymap.c` is required, and if the rest of the files are not found the default options will be chosen.

* `config.h`: the options to configure your keymap
* `keymap.c`: all of your keymap code, required
* `rules.mk`: the features of QMK that are enabled
* `readme.md`: a description of your keymap, how others might use it, and explanations of features. Please upload images to a service like imgur.

# The `config.h` file

There are 2 `config.h` locations:

* keyboard (`/keyboards/<keyboard>/config.h`)
* keymap (`/keyboards/<keyboard>/keymaps/<keymap>/config.h`)

If the keymap `config.h` exists, that file is included by the build system and the keyboard `config.h` is not included. If you wish to override settings in your keymap's `config.h` you will need to include some glue code:

```
#ifndef CONFIG_USER_H
#define CONFIG_USER_H

#include "config_common.h"
```

If you want to override a setting from the parent `config.h` file, you need to `#undef` and then `#define` the setting again, like this:

```c
#undef MY_SETTING
#define MY_SETTING 4
```
