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Simtel MSDOS 1992 September
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D16BIT.MAY
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1986-05-31
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15KB
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385 lines
name window
page ,132
title BIOS Window Extension V1.1
comment \
Copyright 1984 John J. Seal
The Graphic Software Company
348 East Pratt Street
Franklin, IN 46131
This program may be used for any non-commercial purpose
provided that this copyright notice is included.
Commercial use is forbidden without the express written
consent of The Graphic Software Company.
This program allows a window to be defined on the display.
All programs which use the BIOS Write TTY call for output
will work within the window. Other BIOS calls may still be
used for I/O to arbitrary screen positions.
The window is defined by a pair of coordinates specified on
the command line. The only absolute format requirements are
that each coordinate pair start with a left parenthesis and
be separated with a comma. Everything else is optional. The
suggested command format is:
window (ur,lc) to (lr,rc)
ur = upper row
lc = left column
lr = lower row
rc = right column
The new functions serviced by the video interrupt (int 10)
and their corresponding function codes are:
ah = 14 Write TTY
ah = 16 Set window coordinates
ah = 17 Get window coordinates
ah = 18 Get blanking attribute
\
code segment
org 100h ;For COM conversion
assume cs:code
DOS_entry label far ;DOS entry point
jmp install
upper_left label word ;Window coordinates
left db 0
upper db 0
lower_right label word
right db 79
lower db 24
old_int dd ? ;Old interrupt vector
comment \
The new interrupt procedure first filters out the new
services from the old, and passes all old service calls
back to the BIOS.
\
interrupt proc far
sti
cmp ah,14 ;Write TTY
je write_tty
cmp ah,16 ;Set window
je set_window
cmp ah,17 ;Get window
je get_window
cmp ah,18 ;Get blanking
je get_blanking
bios: jmp old_int
comment \
Set window coordinates.
This function call sets the coordinates of a window in the
display area. The window is defined by specifying the upper
left and lower right corners in terms of screen coordinates.
The upper left corner of the screen is position (0,0). The
specified corners are included in the window area.
If the specified coordinates are legal then the window is
cleared, the cursor is homed to the upper left corner, and
al = 0. Otherwise, no action is taken and al = 1.
Entry: ah = 16 (function code)
cx = upper left corner
dx = lower right corner
Exit: al = fail flag (see above)
All registers preserved except ax.
\
set_window: push bx ;Save registers
push cx
push dx
mov al,1
cmp ch,dh ;Check coordinates
ja exit
cmp cl,dl
ja exit
mov upper_left,cx ;Update coordinates
mov lower_right,dx
mov ah,18 ;Read blank attribute
int 10h
mov ax,600h ;Blank entire window
int 10h
mov ah,15 ;Read current page
int 10h
mov dx,cx ;Home cursor
mov ah,2
int 10h
mov al,0
exit: pop dx ;Restore registers
pop cx
pop bx
iret
comment \
Get window coordinates.
This function call returns the coordinates of the upper left
and lower right corners of the current display window.
Entry: ah = 17 (function code)
Exit: cx = upper left corner
dx = lower right corner
All registers preserved except cx and dx.
\
get_window: mov cx,upper_left ;Read coordinates
mov dx,lower_right
iret
comment \
Get blanking attribute.
This function call returns the attribute of the character
at the current cursor position, if in alpha mode, or the
background color (0) if in graphics mode. The resulting
attribute is meant to be used when scrolling the screen.
Entry: ah = 18 (function code)
Exit: bh = blanking attribute
All registers preserved except bx.
\
get_blanking: push ax ;Save registers
mov ah,15 ;Read current page
int 10h
xor ah,ah ;Background color
cmp al,3 ;Check for alpha modes
jbe alpha
cmp al,6 ;Check for graphics
jbe graphics
alpha: mov ah,8 ;Read attribute
int 10h
graphics: mov bh,ah ;Return attribute
pop ax
iret
comment \
Write TTY.
This function call replaces the old call of the same name.
It performs the same functions but allows the current window
to be user defined instead of the whole screen.
Entry: ah = 14 (function code)
al = character to write
bh = page number to write on
bl = foreground color (in graphics modes)
All registers preserved.
\
write_tty: cmp al,7 ;Let BIOS ring the bell
je bios
push ax ;Save registers
push bx
push cx
push dx
push ax ;Save character
mov ah,3 ;Read cursor position
int 10h
pop ax ;Recover character
; Check for unprintable control characters
cmp al,8 ;Backspace
je bs
cmp al,10 ;Line feed
je lf
cmp al,13 ;Carriage return
je cr
; Character is printable
mov cx,1 ;Print character
mov ah,10
int 10h
inc dl ;Advance cursor
cmp dl,right
jbe set_cursor
; Right edge of window exceeded - wrap to next line
mov dl,left
lf: inc dh
cmp dh,lower
jbe set_cursor
; Lower edge of window exceeded - scroll window up
push bx ;Save page
mov ah,18 ;Read blank attribute
int 10h
mov cx,upper_left ;Scroll window up
mov dx,lower_right
mov ax,601h
int 10h
pop bx ;Restore page
; Return cursor to left-hand edge
cr: mov dl,left ;Carriage return
; Set cursor to new position
set_cursor: mov ah,2 ;Set cursor
int 10h
pop dx ;Restore registers
pop cx
pop bx
pop ax
iret
; Backspace does not wrap past left edge of window
bs: dec dl ;Back up
cmp dl,left ;Past left edge?
jb cr ;Yes, reset cursor
jmp set_cursor ;No, leave it alone
interrupt endp
greeting db 13,10
db 218,30 dup (196),191,13,10
db 179,' The Graphic Software Company ',179,13,10
db 179,' BIOS Window Extension V1.1 ',179,13,10
db 192,30 dup (196),217,13,10,'$'
error_msg db 13,10,'Invalid window coordinates',13,10,'$'
comment \
The install procedure is invoked through the DOS entry point
when the program is first run. It installs the new interrupt
and prints a message on the console. When done, it returns to
DOS and allows the space it occupies itself to be reclaimed.
The program first tests whether the BIOS extensions are already
installed. If they are not, this can be detected by the fact
that a call to an illegal function will return without altering
any registers.
\
assume ds:code
install proc near
mov ah,17 ;Read coordinates
int 10h
inc cl ;Alter their value
mov al,cl
int 10h ;Read them again
cmp al,cl ;Test for difference
pushf
jne installed
; Install BIOS extensions
mov dx,offset greeting ;Report installation
mov ah,9
int 21h
mov ax,3510h ;Read old interrupt
int 21h
mov word ptr old_int,bx ;Save old interrupt
mov word ptr old_int+2,es
mov dx,offset interrupt ;Install new interrupt
mov ax,2510h
int 21h
; BIOS extensions are installed now
installed: push cs ;Point to command tail
pop es
mov di,81h
mov cx,7fh ;Read coordinates
mov al,'('
repne scasb ;Find first pair
call num_pair
push dx
repne scasb ;Find second pair
call num_pair
pop cx
mov ah,16 ;Set coordinates
int 10h
or al,al ;Test legality
jz legal
; Window coordinates are illegal
mov dx,offset error_msg ;Print error message
mov ah,9
int 21h
; Terminate program in appropriate manner
legal: popf ;Check residency
jne resident
mov dx,offset greeting ;Make resident
int 27h
resident: int 20h ;Already resident
num_pair proc near
push bx
call number ;Read first number
mov bh,dl
call number ;Read second number
mov dh,bh
pop bx
ret ;Row/Col pair in dx
num_pair endp
number proc near
push ax
push bx
mov al,' ' ;Skip leading blanks
repe scasb
dec di
mov bl,10 ;Decimal multiplier
xor ax,ax
xor dx,dx
digit: xchg ax,dx ;Multiply by 10
mul bl
add ax,dx ;Add new digit
xchg ax,dx
mov al,es:[di] ;Read next character
inc di
sub al,'0' ;Normalize it
cmp al,'9' ;Check for digits
jbe digit
pop bx
pop ax
ret ;Number in dx
number endp
install endp
code ends
end DOS_entry ;Must be far label
