The operating system DJS200/XT1G is a general drum operating system designed for the computers DJS200/20 and DJS200/10. This paper discribes the structucre and the implementation of the operating system. The function of XT1G is realized by a kernel and a number of processes which are placed at various hierarchical levels. The synchronization mechanisms adopted are mainly communication primitives

also the priority schedule approach and the read/write list primitives are introduced The resource scheduling uses different algorithms for various resources of the system. The structure can guarantee the. correctness

efficiency and adaptability of the system. This paper shortly presents the key points of the implementation of the system. Finally

a multiprogramming example is given.