# Introduction | QMK Firmware
Documentation for QMK Firmware

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# 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's tmk_keyboard project. The original TMK code, with modifications, can be found in the `tmk_core` folder. The QMK additions to the project may be found in the `quantum` folder. Keyboard projects may be found in the `keyboards` folder.

### Userspace Structure ​

Within the folder `users` is a directory for each user. This is a place for users to put code that they might use between keyboards. See the docs for Userspace feature for more information.

### Keyboard Project Structure ​

Within the folder `keyboards`, its subfolder `handwired` and its vendor and manufacture subdirectories e.g. `clueboard` is a directory for each keyboard project, for example `qmk_firmware/keyboards/clueboard/2x1800`. 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 `rules.mk`.
- `config.h`: The file that sets the default compile time options. Do not edit this file directly, instead use a keymap specific `config.h`.
- `info.json`: The file used for setting layout for QMK Configurator. See Configurator Support for more information.
- `readme.md`: A brief overview of the keyboard.
- `<keyboardName>.h`: This file is where the keyboard layout is defined against the keyboard's switch matrix.
- `<keyboardName>.c`: This file is where you can find custom code for the keyboard.

For more information on project structure, see QMK Keyboard Guidelines.

### 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 3 possible `config.h` locations:

- keyboard (`/keyboards/<keyboard>/config.h`)
- userspace (`/users/<user>/config.h`)
- keymap (`/keyboards/<keyboard>/keymaps/<keymap>/config.h`)

The build system automatically picks up the config files in the above order. If you wish to override any setting set by a previous `config.h` you will need to first include some boilerplate code for the settings you wish to change.

    #pragma once

Then to override a setting from the previous `config.h` file you must `#undef` and then `#define` the setting again.

The boilerplate code and setting look like this together:

    #pragma once

    // overrides go here!
    #undef MY_SETTING
    #define MY_SETTING 4