## Physical Device Driver Reference

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### 5h - Remarks

The physical device driver must perform the following actions:

Return a byte from the device
Set the status WORD in the request header

For input on character devices with a buffer, the physical device driver returns from this function with the busy bit set to 0, along with a copy of the first character in the buffer. The busy bit is set to 1 to indicate no characters in the buffer. This function allows the operating system to look ahead one input character, without blocking in the physical device driver.