## Physical Device Driver Reference

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### Separate Threads

Because character device monitors are part of a data stream, they must process data records rapidly so that they do not delay I/O. A monitor application must be written so the threads that actually read and write the monitor data run at a high priority. They must never perform operations such as I/O or semaphore waits that might cause excessive delay. The monitor application can have other threads running at normal priorities to handle such functions.