Adaptive optics systems rely on a real-time control system which is responsible for receiving wavefront sensor information and computing and applying the necessary correction to the deformable mirrors. Historically, real-time control systems have relied on customised hardware comprised of multiple FPGA and DSP systems, which high complexity. More recently it has been demonstrated that conventional PCs are now sufficiently powerful to to perform this task. In this talk, I will present an open-source real-time control system, DARC, discuss its implementation on the CANARY AO system at the William Herschel Telescope, and cover the algorithms available. Extension to ELT-scale operation will be discussed, including hardware and detector considerations. The internal architecture of this modular system will be presented, with a case being made for its suitability for implementation on any AO system type, on any telescope.