RSX-DAS is a flexible CAMAC-based data acquisition software system that runs on a variety of PDP-11 architectures and under RSX-11 operating systems. Since 1983, five versions of RSX-DAS have been developed at tile Plasma Physics Laboratory, University of California, Los Angeles, U.S.A. and the Institute of Plasma Physics, Academia Sinica, China. The system has modular, multi-tasking and concurrent processing features. The commnunication among seventeen tasks is accomplished through parent/offspring tasking, event flags and shared regions. The user interface to RSX-DAS consists of a set of user friendly commands, indirect command files and menus. The database consists of four static shared regions for the control of data acquisition and display, one dynamic shared region for the data of current shot, and data files for previous shots. The moduiarity of the CAMAC interface software allows operation on several CAMAC organizations, for example a parallel branch or some dedicated crates, and allows easy addition and subtraction of CAMAC hardware.