Traditional reconfigurable computing platforms are designed to be single user and have been acknowledged to be difficult to design applications for. The design tools are still primitive and as reconfigurable computing becomes mainstream the development of new design tools and run time environments is essential. As the number of system gates is reaching 10 million on current FPGAs, there is an increase in demand to share a single FPGA amongst multiple applications. A third party must be introduced to handle the sharing of the FPGA and we therefore introduce the first real single FPGA concurrent multi-user operating system for reconfigurable computers. In this paper we describe the complete operating system for reconfigurable architecture and the implementation details for the first limited multi-user operating system. The first OS is a loader, it allocates FPGA area and it can dynamically partition, place and route applications at run-time. As OS for reconfigurable computing is a new area of research, we also had to develop techniques for regression testing and performance comparison. This involved the development of a test suite.