汇编语言编写DOS下的内存驻留程序(3)

核心提示：mov word ptr New_Keyboard_IO,es ;Segment of interrupt handlermov al,16hmov ah,25hint 21h3.4 检查中断矢量这里都是采用COM格式编程,可以建立一个BAT文件来处理写好的程序,以减少击键次数.设BAT文件名为MAKE.BAT:MAS

mov word ptr New_Keyboard_IO,es ;Segment of interrupt handler
mov al,16h
mov ah,25h
int 21h
3.4 检查中断矢量
这里都是采用COM格式编程,可以建立一个BAT文件来处理写好的程序,以减少击键次数.设BAT文件名为MAKE.BAT:
MASM %1
LINK %1
EXE2BIN %1.EXE %1.COM
如果写好的程序名为MACRO.ASM,则可敲入:
C:\MAKE MACRO.ASM
即可.
3.5 显示中断矢量
下面这个例子可以列出所有的重要的中断矢量内容,在刚刚打开PC时,并且没有执行任何驻留程序时,可以发现所有的中断矢量段值都相同,这些地址值所存放的是ROM的程序.当你修改中断矢量之后,就可以利用这个程序观察到中断矢量的变化.以下就是IVEC.ASM的内容:
cseg segment para public 'CODE'
org 100h
jmp start
assume cs:cseg,ds:cseg
start: 
mov bx,cs ;Make data seg be the same as
mov ds,bx ;the code seg
call vectors
waitIn:
mov ah,0bh
int 21h
cmp al,0ffh
jne waitIn
mov ah,4ch
int 21h
;****************************************************************************
;Scan through display table,prinying two vectors per line
;If any record has an interrupt #=zero,this indicates
;end of the table.
;****************************************************************************
mov di,offset disptab ;Pointer to start of table
mov dh,0 ;Zero out top half of DX
vloop: 
mov dl,[di] ;Get the interrupt number
cmp dl,0 ;If it's zero,we are done
je vdone ;so exit loop
add di,1 ;Advance pointer 1 byte
mov si,[di] ;Get pointer to description
call dvector ;Call the display routine
add di,2 ;Get the interrupt number
mov dl,[di] ;Advance to the next record 
cmp dl,0 ;If it's zero,we are done
je vdone ;so exit loop
add di,1 ;Advance pointer 1 byte
mov si,[di] ;get pointer to description
call dvector ;Call the display routine
add di,2 ;Advance to the next record
jmp vloop 
vdone: ;Print final CRLF
ret
vectors endp
;----------------------------------------------------------------------------
;Displays an interrupt vector.Display is in the form of
;,<INTERRUPT#>, :
;where ,and
;are all dexadecimal numbers
;Call with
;DX -interrupt number
;DS:SI -pointer to banner string
;----------------------------------------------------------------------------
dvector proc near
call dstring ;Display the string in DS:SI
call dbyte ;Display the byte in DL
call dspace ;Display a space
call dspace
;
mov al,dl ;move the interrupt number to AL
mov ah,35h ;Function is Get interrupt vector
int 21h
mov dx,bx ;Move BX to DX so we can display
call ddword ;double-word in ES:DX
call dEndFra
call dcrlf ;Display a newline
ret
dvector endp 
;----------------------------------------------------------------------------
;DS:SI points to ASCII string to be printed
;----------------------------------------------------------------------------
dstring proc near
push si
push ax
dis: mov al,[si] ;Fetch the next character
cmp al,0 ;If it's zero,we are done
je disdone 
call dchar ;If not,point it
inc si ;Advance pointer to nest char
jmp dis
disdone:pop ax
pop si
ret
dstring endp
;---------------------------------------------------------------------------- 
;ES:DX contains double word to be displayed
;----------------------------------------------------------------------------
ddword proc near
push dx ;Save offset temporarily
mov dx,es ;Move segment to DX
call dsword ;Display segment
call dcolon ;Print a ";"
; call dcrlf
pop dx ;Restore offset to DX
call dsword ;Display offset
ret
ddword endp
;----------------------------------------------------------------------------
;DX containes single word to be displayed
;----------------------------------------------------------------------------
dsword proc near
push dx ;Save low byte temporarily
mov dl,dh ;Move high byte to low byte
call dbyte ;Display high byte
pop dx ;Restore low byte to DL
call dbyte ;Display low byte
ret
dsword endp
;----------------------------------------------------------------------------
;DL contains byte to be displayed
;----------------------------------------------------------------------------
dbyte proc near
push ax ;Save any registers used