An open, reconfigurable and modular monitoring and control system is presented for CNC machine tools. The CNC operating system is a fully integrated an open real-time, preemptive DSP operating system and a Windows NT application. It has vendor neutral architecture, and supports multiple DSP boards and multiple host computers for distributed operation. The system’s transparent communication protocol allows connection between software modules on the same or different DSP boards and host computers. The connections can be set up at runtime via a scripting language. The operating system allows modular integration of new functions developed in C language, and can be reconfigured to control robots, machine tools or processes, using simple script commands. The system can be used as an open architecture, modular operating system for the progressive development of real time signal processing, motion and process control applications running in WINDOWS NT and DSP environments. Sample applications for machine tool control and sensor assisted machining applications are presented.