这尤其是在多处理器系统方面的一个问题，超过程序可能存取一个资料项目哪里。

This is especially a problem on multiprocessor systems where more than one process may be accessing a datum.

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第一，应用程序无法直接存取周边设备，必须呼叫作业系统核心以取得或设定周边资料。

First, the application cannot directly access the peripherals, but instead must call the operating system core to get or set peripheral data.

youdao

多个执行绪可能需要存取共用资料库，或是对一组系统变数进行更新。

Multiple threads may need to access a Shared database, for instance, or make updates to a set of system variables.

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