$CPU 8086          ' make compatible with XT systems
$LIB ALL OFF       ' turn off all PowerBASIC libraries
$ERROR ALL OFF     ' turn off all PowerBASIC error checking
$OPTIMIZE SIZE     ' optimize for smaller code
 $COMPILE UNIT      ' compile to a UNIT (.PBU)
'$COMPILE EXE       ' compile to a UNIT (.PBU)

DEFINT A-Z         ' Required for all numeric functions, forces PB to not
                   ' include floating point in UNIT (makes it smaller)
'/*------------------------------------------------------------------*/
$CODE SEG "MLIB5"
'/*------------------------------------------------------------------*/
FUNCTION ISDRIVEREADY( BYVAL Drive$ ) PUBLIC AS INTEGER
' This FUNCTION returns -1 (true) if the drive is ready, or 0 (false),
' if the drive is not ready, or the drive letter is an invalid drive.
' It will NOT recognize a CD-ROM drive as being ready.

  DIM DriveNum AS LOCAL INTEGER
  DIM DriveIsReady AS LOCAL INTEGER

  DriveNum = ( ASC( Drive$ ) OR 32 ) - 97
  DriveIsReady = -1 'assume drive will be ready

  ! push DS
  ! xor  AX, AX
  ! mov  DX, DriveNum     ; zero - based drive numbering used
  ! int  &H13             ; CALL BIOS TO RESET the drive controller
  ! mov  AX, &H401
  ! mov  CX, &H101
  ! mov  DX, DriveNum
  ! int  &H13
  ! mov  AX, &H401
  ! mov  CX, &H101
  ! mov  DX, DriveNum
  ! int  &H13
  ! jnc  DriveOK          ; carry set could be a fixed disk
  ! mov  AH, &H1C         ; so LET us look, USING DOS
  ! mov  DX, DriveNum
  ! inc  DX               ; one - based drive numbering used
  ! int  &H21
  ! cmp  DX, &HFF
  ! je   DriveOK
  ! mov  AX, [BX]
  ! cmp  AX, &HF8
  ! je   DriveOK
  ! mov  DriveIsReady, 0

DriveOK:

  ! pop DS

  DriveReady = DriveIsReady
  IF DriveReady = -1 THEN FUNCTION = 1 ELSE FUNCTION = 0

END FUNCTION
'/*------------------------------------------------------------------*/
'  $INCLUDE "C:\CODE\MLIB\MLIB.INC"
'  CLS
'  PRINT "CHECKING DRIVE A = " ISDRIVEREADY("A")
'  PRINT "CHECKING DRIVE C = " ISDRIVEREADY("C")
'  Y$ = GETKEY
'  PRINT "CHECKING DRIVE A = " ISDRIVEREADY("A")
'  Y$ = GETKEY