Bare machine (or bare metal), in computer parlance, means a computer without its operating system. Modern operating systems evolved through various stages, from elementary to the present day complex, highly sensitive real-time systems. After the development of programmable computers (which did not require physical changes to run different programs) but prior to the development of operating systems, programs were fed to the computer system directly using machine language by the programmers without any system software support. This approach is termed the "bare machine" approach in the development of operating systems. Today it is mostly applicable to embedded systems and firmware, while everyday programs are run by a runtime system within an operating system.