汇编源码--drives

; Drive detection by: Lee Hamel (hamell@cs.pdx.edu) - July 6th, 1994
; Partial credit to : Paul Schlyter
;
; Goes thru drives A-Z and determines if they:
; 1) Exist
; 2) Are removable or fixed
; 3) Are local, remote, or shared
; 4) Are a floppy, hard, RAM, subst, or CD-ROM drive
.model tiny
.286
DRIVEXISTS      EQU     1
REMOVEDRV       EQU     0
FIXEDDRV        EQU     1
LOCALDRV        EQU     0
REMOTEDRV       EQU     1
SHAREDRV        EQU     2
FLOPPY          EQU     0
HARD            EQU     1
RAM             EQU     2
SUBST           EQU     3
CDROM           EQU     4
.code
        org     100h
start:          mov     ah,19h
                int     21h             ; get start drive
                mov     ,al
                mov     ax,40h
                mov     es,ax
                mov     bh,es:     ; 40:10h is # of floppies-1
                shr     bh,6
                inc     bh              ; # of actual floppy drives
                mov     bl,1
                mov     di,offset drives
nextchkfloppy:  mov     ax,4409h        ; check if drive exists
                int     21h
                jc      nextsetfloppy
                test    dh,10000000b    ; check if SUBST drive
                jz      chkfloppy
                dec     bh              ; dec actual drive count
                mov     byte ptr ,SUBST
setfloppyexist: mov     byte ptr ,DRIVEXISTS
                jmp     nextsetfloppy
chkfloppy:      dec     bh              ; dec actual drive count
                js      nextsetfloppy
                mov     byte ptr ,REMOVEDRV
                mov     byte ptr ,FLOPPY
                jmp     setfloppyexist
nextsetfloppy:  add     di,4
                inc     bl
                cmp     bl,2            ; if B then jump back
                je      nextchkfloppy
                mov     ch,24           ; loop 24 times (drives C - Z)
                mov     cl,3            ; start at C:
drivechkloop:   mov     ax,4409h        ; check if drive exists
                mov     bl,cl           ; set drive letter
                int     21h             ; 0 = default, 1 = A:, etc.
                jc      nextsetdrv
                mov     byte ptr ,DRIVEXISTS
                mov     ax,4408h        ; check if removable
                int     21h
                mov     byte ptr ,al      ; set REMOVABLE or FIXED
                mov     bx,dx
                mov     dl,dh
                shr     dl,7
                and     dh,00010000b
                shr     dh,4
                mov     byte ptr ,dh      ; set REMOTE or LOCAL
                or      dl,dl                   ; if not SUBST, then jump
                jz      chkremote
                mov     byte ptr ,SUBST
                jmp     nextsetdrv
chkremote:      cmp     dh,REMOTEDRV    ; if REMOTE, then check for CD ROM
                je      chkcdrom
                test    bh,00000010b    ; sharable?
                jz      drivenoshare
                mov     byte ptr ,SHAREDRV
drivenoshare:   test    bl,00000010b    ; RAM drive?
                jnz     nextsetdrv
                mov     byte ptr ,RAM
                jmp     nextsetdrv
chkcdrom:       push    cx
                mov     ax,1500h
                xor     bx,bx
                int     2fh
                pop     cx
                or      bx,bx           ; MSCDEX driver found?
                jz      nextsetdrv      ; if not, jump to next drive setup
                mov     ax,150bh
                dec     cl              ; 0=A:, etc.
                int     2fh
                inc     cl
                or      ax,ax
                jz      nextsetdrv      ; drive supported by MSCDEX?
                mov     byte ptr ,CDROM
nextsetdrv:     add     di,4
                inc     cl
                dec     ch
                jnz     drivechkloop
                mov     ah,0eh
                mov     dl,
                int     21h             ; reset start drive
                mov     cl,'A'          ; output all existing drives
                mov     di,offset drives
                mov     ah,9
drvdumploop:    cmp     byte ptr ,DRIVEXISTS
                jne     nextdrvdump
                mov     al,cl
                int     29h
                xor     dh,dh
                mov     dl,byte ptr 
                shl     dx,4
                add     dx,offset removablemsg
                int     21h
                xor     dh,dh
                mov     dl,byte ptr 
                shl     dx,3
                add     dx,offset localmsg
                int     21h
                xor     dh,dh
                mov     dl,byte ptr 
                shl     dx,3
                add     dx,offset typemsg
                int     21h
                mov     dx,offset crlf
                int     21h
nextdrvdump:    add     di,4
                inc     cl
                cmp     cl,'Z'
                jbe     drvdumploop
                ret
curdrive        db      0
drives          db      26 dup(0,1,0,1)
        ; default to not exist, fixed, local, hard drive
crlf            db      10,13,'$'
removablemsg    db      ':    Removable $'
                db      ':        Fixed $'
localmsg        db      'Local  $'
                db      'Remote $'
                db      'Shared $'
typemsg         db      'Floppy $'
                db      'Hard   $'
                db      'RAM    $'
                db      'Subst  $'
                db      'CD-ROM $'
        end     start