Before you can build C or C++ programs, you need a way to manage the steps involved—like compiling source files, linking them together, and handling dependencies between them. This process is managed by a build system. Classic build systems such as Make or custom shell scripts have been used for decades, but they often require manual configuration and can be difficult to adapt to different operating systems or compilers. When you want your project to work on Windows, macOS, and Linux, you quickly run into challenges: file paths differ, available compilers change, and the commands to build or link your project can vary widely. Maintaining separate build scripts for each platform is time-consuming and error-prone, making cross-platform development a real headache.

CMake was created to solve these problems. It is an open-source, cross-platform build system generator that was first released in 2000. Unlike traditional build systems, CMake does not actually build your code directly. Instead, it generates native build scripts—such as Makefiles for Unix-like systems or Visual Studio project files for Windows—based on a simple, platform-independent configuration file. This file, usually called CMakeLists.txt, describes your project structure, source files, dependencies, and build rules in a way that CMake can understand. By doing so, CMake allows you to write your build instructions once and generate the appropriate build scripts for any supported platform or compiler, greatly simplifying the process of building C or C++ projects across different environments.