' Check for available drives.
' (c) 1996 Eternity Software
' Code by Michael Hemmelder
' Last modification : 15 - 02 - 1996
' Status: Public Domain

cls
Print "Available drives:"
print Drives$(0)		' print available drives without dd's
Print Drives$(1)		' print available drives with dd's

FUNCTION drives$(dd)
   ' returns a string containing the available drives
   ' dd - 0 = String does not contain available disk drives
   '      1 = String contains available disk drives
   '
   if dd = 1 then                         ' Check parameter
    start = 0                             ' Include disk drives
   else
       start = 2                          ' Do not include disk drives
   end if
   od = GetCurDrive                       ' Save current drive
   for t=start to 25                      ' Loop until drive = z
      changedrive(t)                      ' Change to drive
      tu = getcurdrive                    ' What is the current drive?
      if t = tu then                      ' Is it the same as the counter?
         dri$ = dri$ + chr$(t + 65)       ' Yes, this drive is available
      end if
   next t
   ChangeDrive od                         ' Restore current drive
   drives$ = dri$                         ' result of function
END FUNCTION

FUNCTION GetCurDrive
   ' Returns the current drive
   '
	REG 1,&H1900
	CALL INTERRUPT &H21
	GetCurDrive = VAL(RIGHT$(STR$(REG(1)),2))
END FUNCTION

SUB ChangeDrive(dr)
   ' Changes current drive
   ' dr = drive no. to change to (a=0 b=1 c=2 ...)
   '
   de$ = hex$(dr)
	REG 1,&H0E00
   REG 4,dr
   CALL INTERRUPT &H21
END SUB