Chapter 15 examples
BIOS-level programming
Variation on keybd.asm
Keybd2.asm code…
.data;;;I added these messages
charis byte "char is=",0
scan byte "scan code=",0
ascii byte "ascii code=",0
.code
main PROC
mov ax,@data
mov ds,ax
call ClrScr
; clear screen
L1: mov ah,10h
; keyboard input
int 16h ; using BIOS
push ax
push ax
mov edx, offset charis
call writestring
mov dl,al
push ax
mov ah,2
int 21h
exe in p drive
call ClrScr ; clear screen
pop ax
call crlf
and eax,0ff00h
mov edx, offset scan
call writestring
shl ax,8
call writeInt
call crlf
mov edx, offset ascii
call writestring
pop ax
and ax,0ffh
call writeInt
call crlf
pop ax
cmp al,1Bh ; ESC key pressed?
jne L1
; no: repeat the loop
Clearing the type-ahead buffer
• If the user is typing keys in some loop (in a
game situation, for example) and the
program is waiting for a particular key
press, you may need to clear the typeahead buffer
INCLUDE Irvine16.inc
ClearKeyboard PROTO, scanCode:BYTE
ESC_key = 1
; scan code
.code
main PROC
L1: ;------------------------- LOOP BODY
; Display a dot, to show program's progress
mov ah,2
mov dl,'.'
int 21h
mov eax,300
; delay for 300 ms
call Delay
;------------------------INVOKE ClearKeyboard,ESC_key
jnz L1
; continue loop if ZF=0
quit:
call Clrscr
exit
main ENDP
; check for Esc key
clearkbd
;--------------------------------------------------ClearKeyboard PROC,
scanCode:BYTE
;
; Clears the keyboard, while checking for a
; particular scan code.
; Receives: keyboard scan code
; Returns: Zero flag set if the ASCII code is
; found; otherwise, Zero flag is clear.
;--------------------------------------------------push ax
L1:
mov ah,11h
; check keyboard buffer
int 16h
; any key pressed?
jz noKey ; no: exit now (ZF=0)
mov ah,10h
; yes: remove from buffer
int 16h
cmp ah,scanCode
; was it the exit key?
je quit
; yes: exit now (ZF=1)
jmp L1
; no: check buffer again
noKey:
; no key pressed
or al,1
; clear zero flag
quit:
pop ax
ret
ClearKeyboard ENDP
END main
Not too impressive
getting keyboard flags directly
kbdseg dw 0040h
kbdofs dw 17h
string byte 'the keyboard settings',0ah,0dh,0
flags word ?
.code
main PROC
mov ax,@data
mov ds,ax
mov ax,kbdseg
mov es,ax
mov di,kbdofs
xor eax,eax
mov al, byte ptr ES:[di]
inc di
mov ah,byte ptr ES:[di]
mov flags,ax
call writebin
getting keyboard flags indirectly
xor eax,eax
mov ah,12h
int 16h
mov flags,ax
call writebin
Keyboard flags: note 1s for caps and
numlock toggle keys (table pg 496)
C:\Masm615\Examples\ch15>FLAGS
0000 0000 0110 0000
C:\Masm615\Examples\ch15>FLAGS2
0000 0000 0110 0000
C:\Masm615\Examples\ch15>
Video display: 3 levels
1. Use DOS int 21h to put stuff on the
screen
2. Use BIOS int 10h to put stuff on screen
(no output redirect allowed)
3. Direct video access…write chars directly
onto screen (see keyboard flags version
for example of how to set seg and ofset)
Video using int 10h
• Each color pixel is generated by an electron
beam with r-g-b components A fourth channel
control intensity, in the format:
• I-R-G-B
• Text table pg 500 shows bit setting for various
colors.
• In color text mode, each character has an
attribute byte consisting of 2 4-bit color settings
for background and foreground. (bottom pg 500)
Int 10h
• Text pg 501 has a list of int 10h function
codes
• These include reading characters from the
screen, writing chars or pixels onto the
screen
Txt pg 502 lists video modes
Mode
Resolution
colors
0
40X25
1
1
40X25
16
2
80X25
2
3
80X25
16
7
80X25
2
14h
132X25
16
Int 10h functions
• Get current video mode and save it before
setting a new video mode:
Int10h, function ah=0 sets mode in al.
• Function 1 sets the cursor size
• Function 2 sets cursor position
(dh,dl=row,col; bh=videopage)
Int 10h functions
• Function 3=get curpos & size
• Text has sample routines pg 545 to show/hide
the cursor.. Here’s an example:
Showcur proc
Mov ah,1
Mov cx,0607h;default size
int 10h
Ret
Showcur endp
Writing (color) text to a window… text example
TextWin.asm (left out a few lines)
; Scroll a window.
mov ax,0600h ; scroll window
mov bh,00011110b
; yellow on blue
mov cx,050Ah ; upper-left corner
mov dx,0A30h ; lower-right corner
int 10h
; Position the cursor inside the window.
mov ah,2
; set cursor position
mov dx,0714h ; row 7, col 20
mov bh,0
; video page 0
int 10h
; Write some text in the window.
mov dx,OFFSET message
call WriteString
; Wait for a keypress.
mov ah,10h
int 16h
exit
Text example… colorstring main proc
call ClrScr
call EnableBlinking
mov cx,SIZEOF string
mov si,OFFSET string
L1: push cx
; save loop counter
mov ah,9
; write character/attribute
mov al,[si]
; character to display
mov bh,0
; video page 0
mov bl,color
; attribute
or bl,ATTRIB_HI
; set blink/intensity bit
mov cx,1
; display it one time
int 10h
mov cx,1
; advance cursor to
call AdvanceCursor
; next screen column
inc color
; next color
inc si ; next character
pop cx
; restore loop counter
Loop L1
call Crlf
exit
EnableBlinking PROC
EnableBlinking PROC
;
; Enable blinking (using the high bit of color
; attributes). In MS-Windows, this only works if
; the program is running in full-screen mode.
; Receives: nothing.
; Returns: nothing
;-------------------------------------------------push ax
push bx
mov ax,1003h
mov bl,1
; blinking is enabled
int 10h
pop bx
pop ax
ret
EnableBlinking ENDP
AdvanceCursor PROC
AdvanceCursor PROC
;
; Advances the cursor n columns to the right.
; Receives: CX = number of columns
; Returns: nothing
;-------------------------------------------------pusha
L1:
push cx
; save loop counter
mov ah,3
; get cursor position
mov bh,0
; into DH, DL
int 10h
; changes CX register!
inc dl
; increment column
mov ah,2
; set cursor position
int 10h
pop cx
; restore loop counter
loop L1
; next column
popa
ret
Run of colorstr
Graphics in int 10h: table of video
graphics modes on pg 512
Mode
6
0dh
0eh
0fh
10h
11h
12h
13h
6ah
Resolution
640X200
320X200
640X200
640X350
640X350
640X480
640X480
320X200
800X600
# colors
2
16
16
2
16
2
16
256
16
functions
• 0Ch write a pixel
• 0dh read a pixel
• See sample calls and parameters in text
Drawline example: Changes mode to full
screen and draws a tiny line segment:
INCLUDE Irvine16.inc
;------------ Video Mode Constants ------------------Mode_06 = 6
; 640 X 200, 2 colors
Mode_0D = 0Dh
; 320 X 200, 16 colors
Mode_0E = 0Eh
; 640 X 200, 16 colors
Mode_0F = 0Fh
; 640 X 350, 2 colors
Mode_10 = 10h
; 640 X 350, 16 colors
Mode_11 = 11h
; 640 X 480, 2 colors
Mode_12 = 12h
; 640 X 480, 16 colors
Mode_13 = 13h
; 320 X 200, 256 colors
Mode_6A = 6Ah
; 800 X 600, 16 colors
More…
.data
saveMode BYTE ?
; save the current video mode
currentX WORD 100
; column number (X-coordinate)
currentY WORD 100
; row number (Y-coordinate)
color BYTE 1
; default color
; In 2-color modes, white = 1
; In 16-color modes, blue = 1
.code
main PROC
mov ax,@data
mov ds,ax
; Save the current video mode
mov ah,0Fh
int 10h
mov saveMode,al
; Switch to a graphics mode
mov ah,0
; set video mode
mov al,Mode_11
int 10h
And the rest
; Draw a straight line
LineLength = 100
mov dx,currentY
mov cx,LineLength
; loop counter
L1:
push cx
mov ah,0Ch
; write pixel
mov al,color
; pixel color
mov bh,0
; video page 0
mov cx,currentX
int 10h
inc currentX
;inc color
; try this for multi-color modes
pop cx
Loop L1
; Wait for a keystroke
mov ah,0
int 16h
; Restore the starting video mode
mov ah,0
; set video mode… this part doesn’t seem to work
mov al,saveMode
; saved video mode
int 10h
exit
main ENDP
Cartesian coordinates
• Need to switch command prompt to full
screen
• Even so, it worked ok when I used
mode11 but not mode6
• Can’t get screen shot in full screen mode
Cartesian example …in slide notes
.data
saveMode BYTE ?
currentX WORD 100
currentY WORD 100
color BYTE 1
; save the current video mode
; column number (X-coordinate)
; row number (Y-coordinate)
; default color
; In 2-color modes, white = 1
; In 16-color modes, blue = 1
.code
main PROC
mov ax,@data
mov ds,ax
; Save the current video mode
mov ah,0Fh
int 10h
mov saveMode,al
; Switch to a graphics mode
mov ah,0
; set video mode
mov al,Mode_11;;;;;note mode6 did not work for me
int 10h
Cartesian example
;
mov cx,X_axisX
mov dx,x_axisY
mov ax,x_axislen
mov bl,white
call horizontal
mov cx,y_axisX
mov dx,y_axisY
mov ax,y_axislen
mov bl,white
call vertical
; Wait for a keystroke
mov ah,0
int 16h
; Restore the starting video mode
mov ah,0
; set video mode
mov al,saveMode
; saved video mode
int 10h
exit
main ENDP
Cartesian example: horizontal line
horizontal proc
.data
currx word ?
.code
pusha
mov currx,cx
mov cx,ax
H1:
push cx
mov al,bl
mov ah,0ch
mov bh,0 ;;page
mov cx,currx
int 10h
inc currx
pop cx
loop h1
popa
ret
horizontal endp
Cartesian example: vertical line
vertical proc
.data
curry word ?
.code
pusha
mov curry,dx
mov currx,cx
mov cx,ax
V1:
push cx
mov al,bl
mov ah,0ch
mov bh,0
mov cx,currx
mov dx,curry
int 10h
inc curry
pop cx
loop V1
popa
ret
vertical endp
END main
Section 15.5 memory mapped
graphics
•
•
•
•
Mode 13h 320X200, 256 color
Text example Mode13.asm
Draws a few blue dots on the screen…
Need to run this in full screen
boatgame
• Code in slide and posted
• Draws a boat and sub
• Uses old medium resolution graphics
mode.
Medium resolution examples
• These examples are based on an older
graphics card but they still work:
• Moveball---in slide notes
• Medres plays cellular automata in medium
resolution
• Boatgame ---ask for source
moveball
• Draws a cyan ball on a blue screen.
• Hit or hold key to move ball rightwards (it
wraps)
• Type ‘x’ to exit
Hr examples from another text: draws a series of
lines in hr –very pretty but can’t get screenshot
.model small
.stack 100h
.386
.code
main proc near
mov ax,@data
mov ds,ax
mov es,ax
mov ah,0fh
int 10h
push ax
call b10mode
call c10display
mov ah,10h
int 16h
pop ax
mov ah,0
int 10h
mov ax,4c00h
int 21h
main endp
b10mode proc near
mov ax,12h
int 10h
mov ah,0bh
mov bx,7
int 10h
ret
b10mode endp
Hr2 continued
c10display proc near
pusha
xor bx,bx
mov cx,64
mov dx,70
@@20:
mov ah,0ch
mov al,bl
int 10h
inc cx
cmp cx, 576;;;row/col delimiters in cx,dc
jne @@20
mov cx,64
inc bl
inc dx
cmp dx,280
jne @@20
popa
ret
c10display endp
end main
Hr4…similar…writes letters
.model small
.stack 100h
.386
video segment at 0b900h;;;page 1
vid db 1000H dup (?)
video ends
.code
main proc near
mov ax,video
mov es,ax
assume es:video
mov ah,0fh
int 10h
push ax;;;save current mode
push bx
mov ax,3
int 10h
mov ax,501h;;page 1
int 10h
call b10display
mov ah,10h;;wait for key
int 16h
hr4
mov ah,5
pop bx
mov al,bh
int 10h
pop ax
xor ah,ah
int 10h
mov ax,4c00h
int 21h
main endp
b10display proc
pusha
mov al,41h
mov ah,1
mov di,820
@@10:
mov cx,60
@@20:
mov es:word ptr[di],ax
add di,2
loop @@20
inc ah
inc al
add di,40
cmp al,51h
jne @@10
popa
ret
b10display endp
end main
hr4
Hr5 draws a block in fullscreen dos window – no screen
shot.. Code in slide notes
.model small
.stack 100h
.386
.data
color db ?
back dw 50
front dw 250
cstart dw 50
cstop dw 250
rstart dw 50
rstop dw 250
red equ 12
grey equ 7
.code
main proc near
mov ax,@data
mov ds,ax
mov es,ax
mov ah,0fh
int 10h
push ax
call b10mode
Hr5 continued (next slide also)
mov color,red
call putblock;;;code on next slide
down:
mov ah,10h
int 16h
pop ax
mov ah,0
int 10h
mov ax,4c00h
int 21h
main endp
putblock proc near
pusha
mov bx,0
mov cx,cstart
mov dx,rstart
@@20:
;check if point cx,dx is in circle
push cx
push dx
sub dx,100
sub cx,100
mov ax,cx
imul cx
push ax
ov ax,dx
imul dx
pop dx
add ax,dx
pop dx
pop cx
cmp ax,10000
jg @@next
mov al,color
mov ah,0ch;;;write dot
int 10h
@@next:
inc cx
cmp cx, cstop
jg @@30
jmp @@20
@@30: mov cx,cstart
inc dx
cmp dx,rstop
jg @@40
jmp @@20
@@40:
popa
ret
putblock endp
end main
More of it
b10mode proc near
mov ax,12h
int 10h
mov ah,0bh
mov bx,7
int 10h
ret
b10mode endp
Other examples
• Game of life (life.exe/.asm) implements a
not too interesting one-dimensional
cellular automata in hr graphics
• Plotdot3 seems to be the same as hr2