Important Notice

The pages on this site contain documentation for very old MS-DOS software, purely for historical purposes. If you're looking for up-to-date documentation, particularly for programming, you should not rely on the information found here, as it will be woefully out of date.

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     63 drive designators (0 through 3Fh) are available.
 
     [Version 3.0+]
     26 drive designators (0 through 19h) are available.
 
     To preserve upward compatibility, new applications should limit
     themselves to the drive letters A-Z (for example, 0 = A and 1 = B).
 
     Logical drives means the total number of block devices: floppy
     disks, simulated disk drives (RAMdisks), and hard-disk drives. A
     single physical hard-disk drive is frequently partitioned into two
     or more logical drives.
 
     In single-drive IBM PC-compatible systems, the value 2 is returned
     in AL, because PC-DOS supports two logical drives (A: and B:) on
     the single physical floppy-disk drive. The actual number of
     physical drives in the system can be determined with ROM BIOS Int
     11h.
 
     [Version 3.0+]
     The value returned in AL is either 5 or the drive code
     corresponding to the LASTDRIVE entry (if any) in CONFIG.SYS,
     whichever is greater.
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