The .cpp file extension is overwhelmingly associated with C++ source code files. C++ is a powerful, general-purpose programming language developed by Bjarne Stroustrup as an extension of the C programming language, or "C with Classes." A .cpp file contains the actual implementation or definition of functions and classes declared in corresponding header files (usually with a .h or .hpp extension). These files are human-readable text files containing instructions written in the C++ syntax. When a programmer wishes to create an executable program, these source files are compiled by a C++ compiler (like GCC, Clang, or MSVC). The compiler translates the human-readable code into machine code. Because C++ is used for everything from operating systems and game engines to high-performance computing and embedded systems, .cpp files are fundamental to a vast array of software development projects. They are plain text and can technically be opened by any text editor, but they are best viewed and edited using an Integrated Development Environment (IDE) that provides syntax highlighting and debugging tools specific to C++.