$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)
'/*------------------------------------------------------------------*/
$CODE SEG "MLIB2"
'/*------------------------------------------------------------------*/
  FUNCTION CURRENTDRIVE() PUBLIC AS STRING
    LOCAL TMP$, TMPSEG??, TMPPTR??, STARTDRIVE?, TESTDRIVE?

    TMP$ = STRING$(26, 32)
    TMPSEG?? = STRSEG(TMP$)
    TMPPTR?? = STRPTR(TMP$)

    ASM PUSH AX
    ASM PUSH CX
    ASM PUSH DX
    ASM PUSH ES
    ASM PUSH DI

    ASM MOV AH, &H19 ;' GET CURRENT DRIVE
    ASM INT &H21
    ASM MOV STARTDRIVE?, AL ;' SAVE AS ORIGINAL DRIVE

    ASM POP DI
    ASM POP ES
    ASM POP DX
    ASM POP CX
    ASM POP AX
    T = 65 + STARTDRIVE?
    FUNCTION = CHR$(T)
  END FUNCTION
'/*------------------------------------------------------------------*/
  FUNCTION GETDRIVELIST() PUBLIC AS STRING
    LOCAL TMP$, TMPSEG??, TMPPTR??, STARTDRIVE?, TESTDRIVE?

    TMP$ = STRING$(26, 32)
    TMPSEG?? = STRSEG(TMP$)
    TMPPTR?? = STRPTR(TMP$)

    ASM PUSH AX
    ASM PUSH CX
    ASM PUSH DX
    ASM PUSH ES
    ASM PUSH DI

    ASM MOV AH, &H19 ;' GET CURRENT DRIVE
    ASM INT &H21
    ASM MOV STARTDRIVE?, AL ;' SAVE AS ORIGINAL DRIVE
    ASM MOV DL, AL ;' "CHANGE" TO CURRENT DRIVE SO AS TO LOAD
    ASM MOV AH, &H0E ;' DOS'S LAST DRIVE VALUE INTO AL
    ASM INT &H21
    ASM XOR CX, CX
    ASM MOV CL, AL ;' MAXIMUM NUMBER OF DRIVES TO TEST=LAST DRIVE

    ASM MOV ES, TMPSEG??
    ASM MOV DI, TMPPTR?? ;' NOW ES:DI -> TMP$
    ASM XOR DX, DX ;' START TRYING WITH 0 (DRIVE A:)
    ASM CLD ;' BE SURE TO WORK FORWARD

    TRYADRIVE:
    ASM MOV DL, TESTDRIVE?
    ASM MOV AH, &H0E ;' ATTEMPT TO CHANGE TO NEW DRIVE IN DL
    ASM INT &H21
    ASM MOV AH, &H19 ;' CHECK SUCCESS BY GETTING CURRENT DRIVE INTO AL
    ASM INT &H21
    ASM CMP AL, TESTDRIVE? ;' WAS CHANGE GOOD?
    ASM JB SKIPPER1 ;' IF NO

    DODRIVELETTER:
    ASM ADD AL, 65 ;' IF YES, FIGURE ASCII OF DRIVE RETURNED ("A"=65)
    ASM STOSB ;' LOAD BYTE TO TMP$

    SKIPPER1:
    ASM INC TESTDRIVE? ;' NEXT DRIVE TO TRY
    ASM LOOP TRYADRIVE

    ASM MOV AH, &H0E ;' RETURN TO ORIGINAL DRIVE
    ASM MOV DL, STARTDRIVE?
    ASM INT &H21

    EXITVDRIVES:
    ASM POP DI
    ASM POP ES
    ASM POP DX
    ASM POP CX
    ASM POP AX

    FUNCTION = RTRIM$(TMP$)
  END FUNCTION
'/*------------------------------------------------------------------*/
   FUNCTION ISDRIVE(OPT$) PUBLIC AS INTEGER
    T$ = GETDRIVELIST
    IF INSTR(1,T$,OPT$) > 0 THEN FUNCTION = 1 ELSE FUNCTION = 0
   END FUNCTION
'/*------------------------------------------------------------------*/
'  $INCLUDE "C:\CODE\MLIB\MLIB.INC"
'  CLS
'  PRINT DRIVELIST
'  PRINT ISDRIVE("A")
'  PRINT ISDRIVE("B")
'  PRINT ISDRIVE("C")
'  PRINT ISDRIVE("D")
'  PRINT ISDRIVE("E")
'  PRINT ISDRIVE("F")
'  PRINT ISDRIVE("Z")
'  PRINT CURRENTDRIVE
'  Y$ = GETKEY
'/*------------------------------------------------------------------*/