Assembly. How to put letters in grahic mode?

Question

How to put letters in graphic mode on position which I want to. Can I display letters in graphic mode or should I define it pixel by pixel in two-dimensional table? Could you give me a example, because I am trying to write animation letters on sinus. Any guides?

Architecture NASM on DOS. It could be 16 or 32 bit. I use DOSBOX on Windows. And compile code by this script: nasm -f obj -g -F borland %1.asm tlink /v %1.obj io.obj, %1.exe

Ok I use fragment from forum:

segment .data
        msg db "Hello world!$"

segment .code
..start:
mov ax, 13h 
int 10h

mov ax, 0a000h
mov es, ax
xor di, di


mov al, 15
mov cx, 100

; start fragment from forum
mov si,msg_text
call print_colored
print_colored:
.loop:
lodsb
cmp al,0
je .done
inc bl
mov ah,0x0E
Int 0x10
jmp .loop
.done:
ret
;end fragment from forum
xor ah, ah
int 16h

mov ax, 3
int 10h   ; go to text mode

mov ax, 4c00h
int 21h 

; variables

msg_text DB "abc"                  ;Text
msgCol  DB 0x07,0x08,0x09,0x0A,0x0B ;Colours
msgXY   DW 0x0E26                   ;Col/Row
msgLen  DB 0x05                     ;Length

And it doesn't work as I want to. It display text in current time when I write it in keyboard. This program display only: http://i62.tinypic.com/e898q8.jpg

In my program I want to put string in psp or even in code and later display on graphic mode screen. So firstly I want to know how to display letter on position which I want to, because later I will try put this string on sinus and try to animate it.

NASM on DOS. It could be 16 or 32 bit. I use DOSBOX on Windows. And compile code by this script: nasm -f obj -g -F borland %1.asm tlink /v %1.obj io.obj, %1.exe — kkkkk, Jul 02 '14 at 13:39
http://stackoverflow.com/questions/13245179/asm-subroutine-to-print-coloured-text-at-specific-location-on-the-screen — sircodesalot, Jul 02 '14 at 13:54
A have edit my question. In this link I have found sth another. — kkkkk, Jul 02 '14 at 14:34
Since you're using mode `13h` you've got a 256-color 320x200 pixel linear bitmap starting at address `0A000h:0000h`. You can draw whatever you want there by writing to individual bytes (pixels) in that bitmap. — Michael, Jul 02 '14 at 14:44
I know that I could write individual pixels, but is there any way to display letten without write letter pixel by pixel? Or mayby I could I set a cursor and ther display? How? — kkkkk, Jul 02 '14 at 15:06
If you want to do pixel-level placement of each character, then I'd say drawing the characters pixel-by-pixel is the easiest. If you're worried about creating a font, you could do this: after you've switched to mode 13h, print all the characters you need as one long string using `int 21h / ah=9`, read the screen contents into an off-screen buffer, and voilà: there's your font for you. — Michael, Jul 02 '14 at 15:10
Accually I need only three letters. It should work not be pretty. So I should create two-dimensional table and set there '1' and '0' for letter. And how now I can to write on position which I want to? In C I would use xposition, yposition and two loops for. But in assembly I haven't wrote a lot. — kkkkk, Jul 02 '14 at 15:18

Dirk Wolfgang Glomp · Accepted Answer · 2014-07-03T08:02:57.550

Inside of the bios of the display device there are some font table and we can get the pointer of it.

RBIL->inter61a.zip->INTERRUP.A
--------V-101130-----------------------------
INT 10 - VIDEO - GET FONT INFORMATION (EGA, MCGA, VGA)
AX = 1130h
BH = pointer specifier
    00h INT 1Fh pointer
    01h INT 43h pointer
    02h ROM 8x14 character font pointer
    03h ROM 8x8 double dot font pointer
    04h ROM 8x8 double dot font (high 128 characters)
    05h ROM alpha alternate (9 by 14) pointer (EGA,VGA)
    06h ROM 8x16 font (MCGA, VGA)
    07h ROM alternate 9x16 font (VGA only) (see #00021)
    11h (UltraVision v2+) 8x20 font (VGA) or 8x19 font (autosync EGA)
    12h (UltraVision v2+) 8x10 font (VGA) or 8x11 font (autosync EGA)
Return: ES:BP = specified pointer
CX    = bytes/character of on-screen font (not the requested font!)
DL    = highest character row on screen
Note:   for UltraVision v2+, the 9xN alternate fonts follow the corresponding
  8xN font at ES:BP+256N
BUG:    the IBM EGA and some other EGA cards return in DL the number of rows on
  screen rather than the highest row number (which is one less).
SeeAlso: AX=1100h,AX=1103h,AX=1120h,INT 1F"SYSTEM DATA",INT 43"VIDEO DATA"

Format of alternate font table [array]:
Offset  Size    Description (Table 00021)
 00h    BYTE    character to be replaced (00h = end of table)
 01h  N BYTEs   graphics data for character, one byte per scan line

Example of the first pointer:

RBIL->inter61b.zip->INTERRUP.E
--------B-1F---------------------------------
INT 1F - SYSTEM DATA - 8x8 GRAPHICS FONT
Desc:   this vector points at 1024 bytes of graphics data, 8 bytes for each
  character 80h-FFh
Notes:  graphics data for characters 00h-7Fh stored at F000h:FA6Eh in 100%
  compatible BIOSes
Under PhysTechSoft's PTS ROM-DOS this table is fictitious.
SeeAlso: INT 10/AX=5000h,INT 43

But we can also use our own:

;-------------------------------------- ────────────────┤
T34 DB 1,0,0,0,0,0,0,1,1,0,0,0,0,0,0,1 ;*      **      *│
    DB 1,1,0,0,0,0,0,1,1,0,0,0,0,0,1,1 ;**     **     **│
    DB 0,1,0,0,0,1,1,1,1,1,1,0,0,0,1,0 ; *   ******   * │
    DB 0,1,1,0,0,1,1,1,1,1,1,0,0,1,1,0 ; **  ******  ** │
    DB 0,1,1,0,0,0,0,1,1,0,0,0,0,1,1,0 ; **    **    ** │
    DB 0,1,1,0,0,0,0,1,1,0,0,0,0,1,1,0 ; **    **    ** │
    DB 0,0,1,0,0,0,0,0,0,0,0,0,0,1,0,0 ;  *          *  │
    DB 0,0,0,1,1,1,0,0,0,0,1,1,1,0,0,0 ;   ***    ***   │
    DB 0,0,0,0,0,0,1,1,1,1,0,0,0,0,0,0 ;      ****      │
    DB 0,0,0,0,0,1,1,1,1,1,1,0,0,0,0,0 ;     ******     │
    DB 0,0,0,0,1,1,0,0,0,0,1,1,0,0,0,0 ;    **    **    │
    DB 0,0,0,1,1,0,0,0,0,0,0,1,1,0,0,0 ;   **      **   │
    DB 0,0,0,1,1,0,0,0,0,0,0,1,1,0,0,0 ;   **      **   │
    DB 0,0,0,1,1,0,0,0,0,0,0,1,1,0,0,0 ;   **      **   │
    DB 0,0,0,0,1,1,0,0,0,0,1,1,0,0,0,0 ;    **    **    │
    DB 0,0,1,1,1,1,0,0,0,0,1,1,1,1,0,0 ;  ****    ****  │
;-------------------------------------- ────────────────┤

Address calculation of the target position= (yposition * scanline) + (xposition * bytes per pixel)
Mode 13h: scanline = 320; bytes per pixel = 1

Example:

mov ax, yposition
mov bx, 320
mul bx
add ax, xposition
mov di, ax    ; Now DI contains the offset address of the target position

Basic example for to read a font from the screen(80x30;640x480; 16 colors):

SCREEN 12
B = -1
G = 2
W = 90
A = 11 * B
R = 140
IF B = 1 THEN R = R - G * 13
P = 3.141592654# / 180
Z$ = "DOS     DIE PC-Zeitschrift"
FOR I = 1 TO LEN(Z$)
LOCATE 1, 1: PRINT MID$(Z$, I, 1)
  FOR X = 0 TO 6
   FOR Y = 1 TO 14
    IF POINT(X, Y) = 15 THEN GOSUB Schreib
   NEXT Y
  NEXT X
  W = W - A
  NEXT I
END
Schreib:
 FOR X1 = 1 TO G
  FOR Y1 = 1 TO G
   IF B = 1 THEN X2 = X * G + X1: Y2 = (Y * G + Y1) + R
   IF B = -1 THEN X2 = X1 - X * G: Y2 = (Y1 - Y * G) + R
    XS = X2 * COS(P * W) - Y2 * SIN(P * W)
    YS = X2 * SIN(P * W) + Y2 * COS(P * W)
      PSET (XS + 320, YS + 240), 15
  NEXT Y1
 NEXT X1
RETURN

I'm trying and trying to put it together and I can't. Nomally in C I would done it like this: for(int i=0; i<16; i++){ for(int j=0; j<16; j++){cout< — kkkkk, Jul 04 '14 at 20:21

score 0 · Answer 2 · answered May 30 '22 at 07:53

0

A faster way to mul by 320:

xor rax, rax
mov ax, yposition
mov bx, ax
shl ax, 8  ; *256
shl bx, 6  ; *64
add ax, bx ; y*256 + y*64 = y*(256+64) = y*320

answered May 30 '22 at 07:53

jsene

1

You're using `xor rax,rax` which wastes a REX prefix, and means this can only assemble for 64-bit mode. With 64 or 32-bit addressing modes https://godbolt.org/z/jWh6hs4Ga shows an LEA to do `y*=5` and an `shl` to do the remaining `y*=64`. So `y*320 + x` takes 3 instructions. On a 386 or later, 16-bit code can use 32-bit addressing modes (including for LEA), so that trick is still applicable to this question about 16-bit real mode. – Peter Cordes May 30 '22 at 08:12
On a modern x86 (like Intel since Nehalem or so), `xor eax,eax` / `imul ax, [yposition], 320` is at least as efficient as the code you show. (1 uop multiply with 3-cycle latency). But much slower on older CPUs. – Peter Cordes May 30 '22 at 08:13

Assembly. How to put letters in grahic mode?

2 Answers2