這個都是過去DOS時代的匯編源碼，雖然已經過去了，但是對於學習匯編還是有幫助的，匯編語言只是程序員一門基礎語言，大多人掌握即可，不一定要深入研究.......
name dev
page 60,132
title 'DEV --- Report installed device drivers'
; DEV --- a utility to report device header information for
; all installed device drivers
;
; Requires PC-DOS or MS-DOS 2.0.
;
; Used in the form:
; A>DEV
;
; version 1.0 December 12, 1984
; Copyright (c) 1984 by Ray Duncan
cr equ 0dh ;ASCII carriage return
lf equ 0ah ;ASCII line feed
blank equ 20h ;ASCII space code
eom equ '$' ;end of string marker
cseg segment para public 'CODE'
assume cs:cseg,ds:data,es:data,ss:stack
dev proc far ;entry point from PC-DOS
push ds ;save DS:0000 for final
xor ax,ax ;return to PC-DOS
push ax
mov ax,data ;make our data segment
mov ds,ax ;addressable via DS and ES.
mov es,ax
mov ah,30h ;check version of PC-DOS.
int 21h
cmp al,2
jae dev1 ;proceed, DOS 2.0 or greater.
mov dx,offset msg2 ;DOS 1.x --- print error message.
jmp dev6
dev1: mov cx,ax ;save DOS version number.
mov ah,15 ;now try and open the "NUL" device.
mov dx,offset nulfcb
int 21h
or al,al ;opened successfully?
jz dev2 ;yes, jump.
mov dx,offset msg1 ;no, print error msg and exit.
jmp dev6
dev2: ;Pick up double pointer to device
;driver chain out of reserved
;area in fcb. This area is mapped
;differently in DOS 2.x and DOS 3.x.
cmp cl,2 ;is this DOS 2.x?
ja dev3 ;no, jump.
mov bx,word ptr nulfcb+25
mov es,word ptr nulfcb+27
jmp dev4
dev3: ;come here if DOS 3.0 or greater.
mov bx,word ptr nulfcb+26
mov es,word ptr nulfcb+28
dev4: call header ;print sign-on message and
;column headings.
dev5: ;trace through the device chain
call prdev ;print device header information
;for driver pointed to by ES:BX.
;pick up addr of next header.
les bx,dword ptr es:[bx]
cmp bx,-1 ;found last one yet?
jne dev5 ;no, try next.
mov dx,offset msg3 ;yes, print "end of device chain".
dev6: mov ah,9 ;print the string whose address
int 21h ;is in DX.
ret ;then return to DOS.
dev endp
header proc near ;print out headings for device
mov dx,offset hdr ;driver information.
mov ah,9
int 21h
ret
header endp
prdev proc near ;print out device driver info.
;ES:BX is pointer to device header,
;which must be preserved.
mov ax,es ;convert segment of device header
mov di,offset inf1
call hexasc
mov ax,bx ;convert offset of device header.
mov di,offset inf2
call hexasc
mov ax,es:[bx+4] ;get attribute word, save a
push ax ;copy of it, then convert it.
mov di,offset inf3
call hexasc
mov ax,es:[bx+6] ;convert ptr to device strategy.
mov di,offset inf4
call hexasc
mov ax,es:[bx+8] ;convert ptr to device int handler.
mov di,offset inf5
call hexasc
;if not char device, clear out name
;field and set number of units.
pop ax ;get back attribute word.
test ax,08000h ;is bit 15 = 1 ?
jnz prdev7 ;yes, it's character dev, jump.
;no, it's block device.
;set flag to skip device name.
mov byte ptr inf8,eom
mov al,es:[bx+10] ;pick up number of units.
aam ;convert to ASCII decimal and
add ax,'00' ;store into output string.
mov byte ptr inf7+1,al
mov byte ptr inf7,ah
;set type = B for Block
mov byte ptr inf6,'B'
jmp prdev9
prdev7: ;if char device, move its 8-character
;name into the output string.
xor si,si
prdev8: mov al,es:[si+bx+10]
mov [si+inf8],al
inc si
cmp si,8
jne prdev8
;remove # of units field.
mov word ptr inf7,' '
;set type = C for Character.
mov byte ptr inf6,'C'
prdev9: mov dx,offset inf ;now print device information
mov ah,9 ;and exit.
int 21h
ret
prdev endp
hexasc proc near ;convert binary word to hex ASCII.
;call with AX=binary value
; DI=addr to store string
;returns AX, CX, DI destroyed.
push ax ;save copy of original value.
mov al,ah
call btoa ;convert upper byte.
add di,2 ;increment output address.
pop ax
call btoa ;convert lower byte.
ret ;return to caller.
hexasc endp
btoa proc near ;convert binary byte to hex ASCII.
;call with AL=binary value
; DI=addr to store string
;returns AX, CX destroyed.
mov ah,al ;save lower nibble.
mov cx,4 ;shift right 4 positions
shr al,cl ;to get upper nibble.
call ascii ;convert 4 bits to ASCII equivalent
mov [di],al ;store into output string.
mov al,ah ;get back lower nibble.
and al,0fh
call ascii ;convert 4 bits to ASCII
mov [di+1],al ;and store into output string.
ret ;back to caller.
btoa endp
ascii proc near ;convert 4 lower bits of AL
add al,'0' ;into the equivalent ASCII char.
cmp al,'9' ;in the range {0...9,A...F}
jle ascii2 ;and return char. in AL.
add al,'A'-'9'-1 ;"fudge factor" for range A-F.
ascii2: ret ;return to caller.
ascii endp
cseg ends
data segment para public 'DATA'
msg1 db cr,lf
db 'Failed to open NUL device.'
db cr,lf,eom
msg2 db cr,lf
db 'Requires DOS version 2 or greater.'
db cr,lf,eom
msg3 db cr,lf
db 'End of device chain.'
db cr,lf,eom
hdr db cr,lf
db 'Addr Attr '
db 'Str Int Type Units Name '
db eom
inf db cr,lf
inf1 db 'XXXX:' ;seg device header
inf2 db 'XXXX ' ;offs device header
inf3 db 'XXXX ' ;attribute
inf4 db 'XXXX ' ;strategy
inf5 db 'XXXX ' ;interrupt handler
inf6 db 'X ' ;type (block or char)
inf7 db 'XX ' ;units (if block device)
inf8 db ' ' ;name (if char device)
db eom
;fcb to open NUL device
nulfcb db 0 ;drive
db 'NUL' ;name of NUL device
db 8 dup (' ')
db 25 dup (0)
data ends
stack segment para stack 'STACK'
db 64 dup (?)
stack ends
end dev
