Loadable Kernel Modules, or LKM, are object files that contain code to extend the running kernel, or so-called base kernel, without the need of a kernel recompilation. Operating systems other than Linux, such as BSD systems, also provide support for LKM's. However, the Linux kernel generally makes far greater and more versatile use of LKM's than other systems. LKM's are typically used to add support for new hardware, filesystems or for adding system calls. When the functionality provided by an LKM is no longer required, it can be unloaded, freeing memory.