page 60,132 title PRTSCRN -- Print the Screen via Interrupt 5 (Shift-PrtScrn) ;****************************************************************************** ; ; I N T 5 ; ; This is a modification of IBM's Interrupt 5 logic. It does the same ; print screen, but if the character to be printed is in the range ; x'00' to x'19' or x'80' to x'99', then a blank is passed instead. ; ; As with IBM's Interrupt 5 logic, the cursor position is saved ; and restored upon completion. The routine runs with ; interrupts enabled. If a subsequent 'Print Screen' key is depressed ; during the time this routine is printing it will be ignored. ; ; Address 50:0 contains the Print Screen status: ; ; 50:0 = 0 Either Print Screen has not been called or upon ; return from a call this indicates a successful ; operation. ; = 1 Print Screen is in progress. ; = 255 Error encountered during printing. ; ; Author Robert S. Russell ; Bootstrap Creations ; 1902 Pomar Way ; Walnut Creek, California 94598 ; ;******************************************************************************* ;------------------------------ ; print status byte ;------------------------------ scrnstat segment at 0h dd 5 dup(?) ; skip int 0-4 int5of dw 1 dup(?) ; int vector for int 5 (offset) int5cs dw 1 dup(?) ; int vector for int 5 (code seg) org 500h status_byte db 1 dup(?) ; 1 = print in progress ; 0 = print not in progress ; 255 = error during print scrnstat ends page code segment public 'code' assume cs:code,ds:scrnstat,ss:code org 100h prtscrn: jmp set_vector ; put initialization code at bottom ; so it can be freed after use. print_screen proc near sti ; enable interrupts push ds ; save regs used push ax push bx push cx ; will be used for cursor limits push dx ; will hold current cursor position mov ax,scrnstat ; a..data segment mov ds,ax ; set data segment cmp status_byte,1 ; is print already in progress? jz exit ; yes, let's get out of here mov status_byte,1 ; indicate print now in progress mov ah,15 ; get the current screen mode int 10h ; [al] = mode ; [ah] = # of cols/line ; [bh] = visual page ;------------------------------------------------------------------------------- ; at this point the columns/line are in ax and the page, if ; color, is in bh. al contains the current video mode ;------------------------------------------------------------------------------- mov cl,ah ; will use cx register to mov ch,25 ; control row and columns. call crlf ; send a cr/lf sequence push cx ; save screen bounds mov ah,3 ; get cursor position int 10h ; and save it pop cx ; recall screen bounds push dx ; recall [bh] = visual page xor dx,dx ; will set cursor position to [0,0] ;------------------------------------------------------------------------------- ; the loop from printloop up to loop_end is the loop to read each cursor ; position from the screen and print the character there. ;------------------------------------------------------------------------------- printloop: mov ah,2 ; indicate new cursor position int 10h ; set cursor position mov ah,8 ; indicate read the character there int 10h ; character now in [al] cmp al,20h ; is char "unprintable"? jb blankit ; yes, so blank it out cmp al,9fh ; printable with hi order bit set? ja printit ; yes, so print it cmp al,80h ; printable with hi order bit cleared? jb printit ; yes, so print it blankit: mov al,20h ; change char to blank printit: push dx ; save cursor position xor dx,dx ; use printer 1 xor ah,ah ; request print the char in [al] int 17h ; print the char pop dx ; restore cursor position test ah,25h ; check for printer error jnz print_err ; quit if error detected inc dl ; move to next column cmp cl,dl ; is this the end of the line? jne printloop ; no, so proceed. xor dl,dl ; return to col 0 (new line) mov ah,dl ; [ah] = 0 push dx ; save new cursor position call crlf ; do cr/lf pop dx ; restore cursor position inc dh ; skip to next line cmp ch,dh ; done? jnz printloop ; no, continue loop_end: pop dx ; get cursor position mov ah,2 ; specify cursor set request int 10h ; restore beginning cursor position mov status_byte,0 ; indicate print screen not in progress jmp short exit ; and get out of here print_err: pop dx ; get cursor position mov ah,2 ; request cursor position set int 10h ; restore cursor position err20: mov status_byte,0ffh ; indicate error exit: pop dx ; restore all the regs pop cx pop bx pop ax pop ds iret print_screen endp ;***** carriage return, line feed subroutine *********************************** crlf proc near xor dx,dx ; select printer 0 xor ah,ah ; send initial cr/lf to printer mov al,10 ; = lf int 17h ; print the line feed xor ah,ah ; clear ah mov al,13 ; = cr int 17h ; print the carriage return ret crlf endp end_print_screen: ;end of resident routine set_vector: push ds xor ax,ax push ax mov ax,scrnstat ; set ds to point to int vector table mov ds,ax ; cli ; disable interrupts so that interrupt ; address doesn't get garbled lea ax,print_screen ; address of print_screen routine mov int5of,ax ; store it in int 5 vector mov int5cs,cs ; and save paragraph address lea dx,end_print_screen ; end of resident interrupt routine sti ; allow interrupt pop ax pop ds int 27h ; terminate but stay resident code ends end prtscrn