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documentation, particularly for programming, you should not rely on the information found here, as it will be woefully out of date.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.
 
▀ [3.0+] 26 drive designators (0 through 19H) are available.
 
▀ To preserve upward compatibility, new applications should limit them-
  selves to the drive letters A-Z (0=A, 1=B, etc.).
 
▀ Logical drives means the total number of block devices: floppy disks,
  simulated disk drives (RAMdisks), and hard-disk drives. A single phys-
  ical 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.
 
▀ [3.0+] The value returned in AL is either 5 or the drive code corre-
  sponding to the LASTDRIVE entry (if any) in CONFIG.SYS, whichever is
  greater.
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