When copying diskettes on a drive whose physical drive number has more than one logical drive letter assigned to it, the operating system issues diskette swap prompts to tell the user which logical drive letter is currently referencing the physical drive number. Function 03h is typically used to avoid this prompt by setting a drive number (corresponding to the drive letter) that is referenced in the next I/O request. The last logical drive letter assigned to the physical drive is determined by calling DSK_GETLOGICALMAP.