| 摘要 |
PURPOSE:To facilitate operation by determining whether access to a nonportable type storage medium is allowed or not on the basis of loading/nonloading data. CONSTITUTION:A device function table 4 contains power-on information on each device, etc., together with M/D data M1 when a storage device is loaded in an external storage device 12 connected to a data processing system 1 or M/D data D0 when not. The M/D data is stored on a magnetic drum DR as a nonportable medium, not to mention a magnetic disk DPU as a portable medium. When access is allowed by a CPU11, an instruction is set in an access instruction register 3, and when there is an instruction which is not accessed by a problem program, a flag 13 is set to ''1''. Then, the flag 13 is set to ''0'' for an instruction which is accessed by a control program. For example, when a request to access an unloaded drum 12-2 is made by the problem program, a check circuit 5 informs the CPU11 that the access is not allowed, and when a request to access is made by the control program, the CPU11 is informed that the access is allowed.
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