SUMMARYUniversity and other educational computer systems may have several thousands to several tens of thousands of users, and several hundreds to several thousands of terminals. When the scale of the system is enlarged, not only is the burden of management increased, but various problems are produced in the system configuration and administration due to the character of the educational system, in which many identical manipulations are performed at the same time. This study was performed in the educational computer system of the Osaka University Information Processing Education Center (now the Cybermedia Center). Through the design and development of a system to support smooth administration of the computer system and classroom activities in the center, the functions needed for support were organized and practical problems were identified, together with methods for their solution. The new system was operated at the Osaka University Information Processing Education Center and was found to contribute greatly to classroom and administration support.

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SUMMARYThe spanning tree maintenance problem for an LAN model in which node processors may halt and recover is considered. An algorithm meeting the conditions that the spanning tree is an L-ary complete tree and that nodes halt or recover singly is presented. The message complexity of this algorithm is shown to be comparable with local computational complexity.