Function 440Eh Get Logical Drive Map

mov bl, Drive ;0 = default, 1 = A, 2 = B, etc.

mov ax, 440Eh ;Get Logical Drive Map

int 21h

jc error_handler ;carry set means error

Get Logical Drive Map (Function 440Eh) determines whether a physical drive has more than one logical drive number and returns the active drive number if it does.

Parameter

Drive

Specifies the drive number to check (0 = default drive, 1 = A, 2 = B, etc.). The function checks the physical drive that corresponds to this logical drive number.

Return Value

If the function is successful, the carry flag is clear and the AL register contains the active drive number for the corresponding physical drive. If the physical drive has only one drive number, the AL register contains 00h.

If the function is not successful, the carry flag is set and the AX register contains an error value, which may be one of the following:

Value

Name

0001h	ERROR_INVALID_FUNCTION
0005h	ERROR_ACCESS_DENIED
000Fh	ERROR_INVALID_DRIVE

Comments

If a program attempts to access the drive by using an inactive drive number, MS-DOS prompts the user with the message “Insert diskette for drive x: and press any key when ready.”