Hello World.

Bazza — Thu Dec 24, 2009 12:55 pm

Author: Bazza

Posted: Thu Dec 24, 2009 12:55 pm

Hey 1sf...

As I know you wouldn`t be able to do it here is the code
to write "Hello World." directly to the CGA memory area.

This is free from MS-DOS interrupt routines/vectors.

The BIOS, INT 10 is not really needed but it DOES serve
TWO purposes, I`ll let you do some research and tell us
all on here what they are...

Fat chance of that ever happening...

Code:

;
; Standard TEXT mode 3 "Hello World." DEMO.
; -----------------------------------------
;
; Copyright (C)1991-2009 B.Walker, (G0LCU). Email to:- wisecracker@tesco.net
; --------------------------------------------------------------------------
;
; "DMA" Hello World.
; -----------------
;
; Assume ORG 100 for MS-DOS and 32768 for MikeOS.
;
; Assembled using the AD86 combination for MS-DOS.
;
;start:
pushf ;Push all necessary registers.
push ax ;Note:- Totally 8088 compatible.
push cx ;
push dx ;
push es ;
push si ;
push di ;
mov ax,0003h ;Set up video mode to "CGA" colour text.
int 10h ;Do it. This does two things in default mode.
cld ;Clear direction flag.
mov ax,0b800h ;Point to CGA memory area.
mov es,ax ;Do it.
mov dx,0 ;Set up the end point for the transfer.
mov si,helloworld ;Set source index to start of text to move.
es: ;Shift to Extended Segment.
mov di,dx ;Set the start if the destination index.
mov cx,12 ;Counter for the number of WORDs to be moved.
repz ;Do it...
movsw ;Print "Hello World." to the CGA memory...
pop di ;Replace all used registers.
pop si ;
pop es ;
pop dx ;
pop cx ;
pop ax ;
popf ;
ret ;
helloworld:
db 72,7,101,7,108,7,108,7,111,7,32,7,87,7,111,7,114,7,108,7,100,7,46,7

The sheer speed of writing directly to any one of the pages of
CGA memory area is breathtaking to say the least.

Have fun... 8-D

EDIT:

I forgot to add, once compiled open up an MS-DOS Prompt
Window, (only available in Vista and above), and see it
working for yourself...

OR, I will post the compiled HW.COM executable somewhere
for you to grab...

Linux Format forums

Hello World.