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TITLE scrn2.asm
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; AUTHOR Tim Spencer - Compuserve [73657,1400]
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; DATE March 15, 1987
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_TEXT SEGMENT BYTE PUBLIC 'CODE'
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_TEXT ENDS
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_DATA SEGMENT WORD PUBLIC 'DATA'
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SCRN STRUC ; screen data structure - defined in video.h
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off dw 0 ; offset (cursor position)
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seg dw 0 ; screen buffer address
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port dw 0 ; status port address
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attrib dw 0 ; attribute to use
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cgacrd dw 0 ; retrace checking enabled if not zero
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SCRN ENDS
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_DATA ENDS
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DGROUP GROUP _DATA
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ASSUME CS:_TEXT, DS:DGROUP, SS:DGROUP, ES:NOTHING
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_TEXT SEGMENT BYTE PUBLIC 'CODE'
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;-----------------------------------------------------------------------;
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; scrn_puts - MSC callable routine for printing a string directly to ;
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; the screen buffer. ;
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; ;
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; Usage: scrn_puts(string, attribute, &structure_name); ;
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;-----------------------------------------------------------------------;
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_DATA SEGMENT
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scrn_puts_args STRUC ; args as pushed by calling program
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dw 0 ; saved bp value
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dw 0 ; return address
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str_ptr dw 0 ; address of string
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sstruc dw 0 ; pointer to SCRN structure
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scrn_puts_args ENDS
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_DATA ENDS
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PUBLIC _scrn_puts
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_scrn_puts PROC NEAR
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push bp ;set up frame pointer
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mov bp,sp
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push di
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push si
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mov si,[bp].str_ptr ; get the string pointer
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mov bx,[bp].sstruc ; get pointer to SCRN structure
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les di,dword ptr[bx].off ; put offset in di, buffer addr in es
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mov ch,byte ptr[bx].attrib ; put attribute in cx
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mov dx,[bx].port ; get status port address
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load_one:
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lodsb ; load a char and advance str ptr
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or al,al ; is it null ?
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jz puts_exit ; yes, lovely chatting. Chow babe.
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mov cl,al ; no, save in cl for a few millisecs
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cmp [bx].cgacrd, 0 ; cga card present?
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jnz swait1 ; yes...go wait
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mov ax,cx ; no.
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stosw ; write it
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jmp short load_one ; as fast as you can!
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swait1:
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in al, dx ; wait for end of retrace
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shr al, 1 ; test horizontal trace bit
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jc swait1 ; loop if still tracing
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cli ; disable writus interuptus
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swait2:
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in al, dx ; now wait until the very moment
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shr al, 1 ; when the next retrace begins
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jnc swait2 ; still waiting...
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mov al,cl ; load the char into al for stosb
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stosb ; write it and update pointer
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sti ; enable interrupts again
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swait3:
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in al, dx ; repeat these steps for the attribute
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shr al, 1
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jc swait3
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cli
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swait4:
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in al, dx
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shr al, 1
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jnc swait4
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mov al,ch ; load the attribute
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stosb
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sti
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jmp short load_one ; and get another
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puts_exit:
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mov [bx].off,di ; save new offset ( cur pos )
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pop si
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pop di
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pop bp
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ret
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_scrn_puts ENDP
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;-----------------------------------------------------------------------;
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; scrn_putca - MSC callable function to print a char and attribute ;
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; directly to the screen buffer. The logical cursor ;
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; position IS UPDATED on return. ;
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; ;
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; Usage: scrn_putca(char, attribute, &structure_name ;
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;-----------------------------------------------------------------------;
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_DATA SEGMENT
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scrn_putca_args STRUC ; args as pushed by calling program
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dw 0 ; saved bp value
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dw 0 ; return address
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pchar dw 0 ; char to write
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pstruc dw 0 ; pointer to SCRN structure
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scrn_putca_args ENDS
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_DATA ENDS
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PUBLIC _scrn_putca
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_scrn_putca PROC NEAR
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push bp ; set up frame pointer
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mov bp,sp
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push di
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mov bx,[bp].pstruc ; get pointer to SCRN structure
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les di,dword ptr[bx].off ; get offset in di, buffer addr in es
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mov dx,[bx].port ; status port address
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mov ch,byte ptr[bx].attrib ; get attribute into ch
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mov cl,byte ptr[bp].pchar ; and char into cl
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cmp [bx].cgacrd, 0 ; cga card present?
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jnz cwait1 ; yes...go wait
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mov ax,cx ; no.
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stosw ; write it
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jmp short cexit ; exit.
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cwait1:
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in al, dx ; wait for end of retrace
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shr al, 1 ; test horizontal trace bit
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jc cwait1 ; loop if still tracing
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cli ; disable writus interuptus
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cwait2:
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in al, dx ; now wait until the very moment
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shr al, 1 ; when the next retrace begins
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jnc cwait2 ; still waiting...
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mov al,cl ; load the char into al for stosb
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stosb ; write it and update pointer
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sti ; enable interrupts again
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cwait3:
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in al, dx ; repeat these steps for the attribute
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shr al, 1
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jc cwait3
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cli
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cwait4:
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in al, dx
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shr al, 1
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jnc cwait4
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mov al,ch ; load the attribute
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stosb
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sti ; whew...all done...enable interrupts
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cexit:
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mov [bx].off, di ; update logical cursor position
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pop di ; (offset) before leaving
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pop bp
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ret
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_scrn_putca ENDP
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;-----------------------------------------------------------------------;
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; _scrn_getca - get char and attrib from screen ;
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; ;
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; usage: char = scrn_getca(&attrib,p_scn_data) ;
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; ;
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;-----------------------------------------------------------------------;
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_DATA SEGMENT
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getca_args STRUC ; input arguments
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dw 0 ; saved BP value
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dw 0 ; return address
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gattrib dw 0 ; store attribute here
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gstruct dw 0 ; pointer to SCRN
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getca_args ENDS
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_DATA ENDS
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PUBLIC _scrn_getca
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_scrn_getca PROC NEAR
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push bp ; set up frame pointer
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mov bp,sp
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push si
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mov bx,[bp].gstruct ; get pointer to SCRN structure
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mov dx,[bx].port ; get status port address
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push ds ; lds uses ds - must save
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lds si,dword ptr[bx].off ; get offset and segment address
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gwait1:
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in al, dx ; wait for end of retrace
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shr al, 1 ; test horizontal trace bit
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jc gwait1 ; loop if still tracing
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cli ; disable writus interuptus
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gwait2:
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in al, dx ; now wait until the very moment
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shr al, 1 ; when the next retrace begins
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jnc gwait2 ; still waiting...
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lodsb ; get the char into al
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sti ; enable interrupts again
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mov cl,al ; save the char in cl
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gwait3:
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in al, dx ; repeat these steps for the attribute
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shr al, 1
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jc gwait3
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cli
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gwait4:
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in al, dx
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shr al, 1
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jnc gwait4
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lodsb ; get the attribute in al
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sti
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pop ds ; restore data segment to norm
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mov word ptr [bx],si ; update offset (logical cursor)
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mov si,word ptr[bp].gattrib ; get address to store attrib
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mov byte ptr [si],al ; store the attribute at "&attrib"
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mov al,cl ; move the char to al and
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xor ah,ah ; zero out ah so that ax = char,
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; the return value
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pop si
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pop bp
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ret
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_scrn_getca ENDP
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_TEXT ENDS
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END
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