# CMake CMakeLists.txt

**CMakeLists.txt** is the build configuration file. It describes what to build, where sources are, dependencies, and build options. Written in CMake's scripting language (imperative, case-insensitive commands).

Minimal example:

```cmake
cmake_minimum_required(VERSION 3.20)
project(MyApp)

add_executable(myapp main.cpp)
```

This declares a project named `MyApp` (creates a binary `myapp` from `main.cpp`). Run `cmake .` to generate build files in the current directory (or `cmake -B build` for out-of-source).

Common commands:

```cmake
cmake_minimum_required(VERSION X.Y)  # minimum CMake version
project(name LANGUAGES C CXX)        # project name, languages used
add_executable(name source.cpp)      # executable target
add_library(name source.cpp)         # library target
target_link_libraries(exe lib)       # link target to library
find_package(PackageName)            # find external package
include_directories(/path/to/headers) # add include path
set(VARIABLE value)                  # set variable
```

Commands are functions: `command(arg1 arg2 ...)`. Lists use semicolons or spaces. Variables are `${VAR}`. Comments start with `#`.

Structure:

1. `cmake_minimum_required` (must be first)
2. `project()` declaration
3. `find_package()` calls for dependencies
4. `add_executable()` or `add_library()` for targets
5. `target_link_libraries()` and other target configuration
6. `install()` rules (optional)

CMake scans source files for dependencies. It's declarative about what you want to build; the generator handles how to actually compile it for your platform.