（汇编源代码 ）PRINT FILE PROGRAM (打印文件)

核心提示：INTRODUCTIONThe following example is a simple program to read a file and print the contents to a standard printer. It gets the filename of the file to print fro

INTRODUCTION

The following example is a simple program to read a file and print the contents to a standard printer. It gets the filename of the file to print from the DOS command prompt input line. The prompt input information is passed to the program in a buffer area of the Program Segment Prefix (PSP). The address of the Program Segment Prefix is passed to the program in the ES and DS registers when the program execution starts. This program checks the keyboard between every character printed for an escape key code to terminate execution of the program.

; This program prints a file defined on the command line
.MODEL small
;************* Stack Section *********************
.STACK 500
;************* Data Section **********************
.DATA
psp_seg　　　 dw　 0
no_cl_mess　　db　"This routine requires that a "
　 db　　"filename be on the command line for printing."
　 db 0dh,0ah,"Please try with a filename.",0dh,0ah,"$"
file_bad_open　db "Bad file open",0dh,0ah,"$"
file_bad_read db "Bad file read",0dh,0ah,"$"
printer_bad_mess　db　 "!! Printer Error !!!!",0dh,0ah,"$"
printing_mess db　"A file is being printed,",0dh,0ah
　 db　 "To stop printing, Press ESC key",0dh,0ah,"$"
filename　　　 db　 128 dup(0)
file_handle　　dw　 0
file_count　　 dw　 0
file_pointer　 dw　 offset file_buffer
file_buffer　　db　 1024 dup(0)
; ************* ----------- *********************
;*************　Code Section　*******************
.CODE
start　　 proc near
　;DS and ES are indexing PSP area
　 mov　al,[DS:80H]　　 ;load AL with size of data line
　 mov　dx,@data　　　　;get segment address of data area
　 mov　ds,dx　　　　　 ;point DS to data area
　 mov　psp_seg,ES　　　;save PSP address
　 cmp　al,1　　　　 ;?? data in DOS command line ??
　 ja　 get_PSP_filename　;branch if data found
　;if here, there is no data on command line
　 ;display error message to user and terminate
　 lea　dx,no_cl_mess
;-------------------------
terminate_display:
　 ;display message indexed by DX then terminate
　 mov　ah,09
　 int 21H　　 ;DOS Call
;-------------------------
terminate_program:
;terminating the program
　　mov　ah,4CH　　;set AH for terminating function
　　mov　al,00　　 ;set terminating code variable
　　int 21H　　　　;call DOS to terminate
;------------------------------------------
; %%%%%%%%%%%%% ----------- %%%%%%%%%%%%%%%
get_PSP_filename:
　;move PSP filename to filename buffer in our data area
　 mov　ax,ds
　 mov　es,ax　　;point ES to data segment
　 mov　ds,psp_seg
　 mov　si,82H　 ;SI source is PSP data area
　 lea　di,filename
　 cld　　　　　 ;make strings go forward
　 get_PSP_data_1:
　　　lodsb　　　;load string data byte
　　　　 ;check for end of filename
　　　cmp　al,21H
　　　　 ;branch if end of string
　　　jb　got_PSP_filename
　　　　 stosb　　 ;store string data byte
　　　　 jmp　get_PSP_data_1
got_PSP_filename:
　 mov　al,0
　 stosb　　 ;make ASCIIZ string with zero end
　 push es
　 pop　ds　 ;reset data segment pointer
;try to open file
　 mov　ah,3dH
　 lea　dx,filename
　 mov　al,0　　 ;read access code
　 int 21H　　　;DOS Call
　 jnc　file_open_ok
　 lea　dx,file_bad_open
　 jmp　terminate_display
;+++++++++++++++++++++++++++++++++++++++++++
;############### +++++++++++ ###############
file_open_ok:
　 ;save file handle
　　mov　file_handle,ax
　　lea dx,printing_mess　;display start message
　　mov　ah,09
　　int 21H　　　 ;DOS Call
file_read:
　 ;read in block of file data
　　mov　ah,3fH
　　lea dx,file_buffer
　　mov　cx,1024
　　mov　bx,file_handle
　　int 21H　　　　;DOS Call
　　jnc　file_read_ok　 ;branch if good read
　　　 ;else read file error occurred
　　　　 ;close file
　　　　mov　ah,3eh
　　　　mov　bx,file_handle
　　　　int 21H
　　　　;index exit error message
　　　　lea　dx,file_bad_read
　　　　jmp　terminate_display
file_read_ok:
　 ;check to see if no more file data
　　cmp　ax,0
　　je　 close_file　 ;branch if no data left
　　;else reset data block size and pointer
　　mov　file_count,ax
　　lea　bx,file_buffer
　　mov　file_pointer,bx
;!!!!!!!!!!!!!!!!!　^^^^^^^^　!!!!!!!!!!!!!!!!!!!!
print_data_block:
　 ;main loop to print block of file data
　　;scan keyboard to check for any keys
　　　mov　ah,1
　　　int 16H
　　　jz　print_data_block_1　;branch if no key
　　 ;get key code out of buffer
　　　mov　 ah,0
　　　int　16H　　　　　;call BIOS keyboard
　　　cmp　 al,01BH　　　　 ;check key code
　　　je　 close_file　　;branch if ESC
print_data_block_1:
　　mov　si,file_pointer
　　mov　al,[si]
　　mov　ah,0
　　mov　dx,0　　　;select LPT1
　　int 17H　　　 ;BIOS Call
　　test ah,25H
　　jnz　printer_error
　　inc　si
　　mov　file_pointer,si
　　dec　file_count
　　jnz　print_data_block　　;loop if more data
　 ;else go read in next block of file data
　　jmp　file_read
;!!!!!!!!!!!!!!!!　^^^^^^^^　!!!!!!!!!!!!!!!!!!!!
close_file:
　　mov　ah,3eh
　　mov　bx,file_handle
　　int　21H　　;DOS Call
　　jmp　terminate_program
;--------------　??????????　-------------------
printer_error:
　　　;index exit error message
　　　lea　dx,printer_bad_mess
　　　jmp　terminate_display
;_______________________________________________
start　endp　　　;end of start procedure
　 end　start　 ;define start as beginning of program