| 摘要 |
A device for monitoring a virtual machine system in which a plurality of operating systems run on a single real machine, includes a register, a monitoring memory, an instruction decoding memory and an address modification circuit. The register stores a first item of information used to distinguish whether a machine instruction is executed by the real machine in real machine mode or in virtual machine mode. The monitoring memory stores a microprogram defining the operations which have to be executed by various machine instructions in real machine mode and in virtual machine mode. The instruction decoding memory stores a start address for the microprogram in the monitoring memory and a second item of information used to designate the switch over in operation for each machine instruction. The address modification circuit modifies the start address of the microprogram, supplied by the machine instruction decoding memory, on the basis of the first and of the second items of information and supplies the modified start address as an address of the monitoring memory. <IMAGE>
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