Fast Text Routine

[rain_storm]

Basically what this does is write a char to the text buffer (offset 0B800h) in text mode only the charictors ascii is held in cl and the colour is held in ch then we store cx to whatever address (which is in si) you want. updating the address by 2 bytes with each write (colour & ascii). this meathod is about ten times faster than using interrupts. I have the routine down to about 34 bytes i think. it will compile with FASM and emu8086.

Code Select Expand


org 100h
mov  al, 03h ; enter text mode
int  10h        ; do it ya lazy bios!
push 0B800h     ; text buffer offset
pop  ds         ; point ds to offset
mov  cl, 58h ; ascii char
call text

text:
  mov [si], cx  ; write colour and char
  add si, 02h   ; update cursor
  inc ch        ; update colour
  cmp si, 0FA0h ; check for screen limit
  jb  text      ; loop if necessary

  inc ch        ; scroll colours
  xor si, si    ; reset cursor
  mov ah, 01h   ; get keyboard input
  int 16h       ; ahem
  jz  text      ; loop if necessary
  ret           ; lets get outta here


[Clyde]

Any chance of adding a .com or exe please dude?

[rain_storm]

its now attached to the first post

[Shockwave]

Nice one mate
Well done.

[Clyde]

Nice going dude

[rdc]

Cool stuff.

[Agent Smith]

This way might be faster (assembles to a 27 byte .com with Tasm/Tlink)

Code Select Expand

.MODEL tiny
.CODE
ORG  100h
entry:
mov  ax, 3       ; set 80x25 text mode (16 colors)
int  10h         ; BIOS video services
mov  ax, 0b800h  ; address of color screen
mov  es, ax      ; ES holds destination segment
xor  di, di      ; zero offset to start of buffer
mov  ah, 15      ; color attribute (white on black)
mov  al, 'X'     ; ASCII character to display
mov  cx, 2000    ; number of words to store
cld              ; auto-increment DI
rep  stosw       ; store AX to ES:DI, CX times
mov  ax, 4c00h   ; terminate with return code 0
int  21h         ; call DOS
END  entry


[rain_storm]

Excellent Thanks Smith Much faster and it will compile with fasm without too much bother

'rep  stosw' <- really gotta start using that

[Shockwave]

Wahey cheers Mr. Smith Have some good Karma.

[Jim]

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mov  ah, 4ch     ; end process
int  21h         ; call DOS

If you're writing a .com file, you can just use ret instead of this.

Jim

[Agent Smith]

That's correct, the OS pushes a zero word onto the stack before jumping to the start of the program, so a near return will pass control back to PSP:0000, which always contains int 20h (Program terminate). This is actually a remnant from MS-DOS version 1.0, which was closely modelled on CP/M.

But exiting via int 21h, AH = 4C (Terminate with return code) became the officially 'approved' method from version 2 onwards.
My code should have really been:

Code Select Expand

  mov ax, 4c00h
  int 21h  as the contents of AL are passed back as the return code.
As my code stands at the moment, 88 is passed back as the return value (i.e. ASCII code for 'X').

Oops  I hope this doesn't mean I'll have to forfeit my Karma 
Shame on you all for not spotting my deliberate error!

[mike_g]

Thats right, hand it back mr Smith...

No seriously I dont know anything about assembler, but I do know that rain_storm is very good at what he does. So if you can improve on his code then you must be very good at what you do so you can have some karma from me Cos I know you hate it really

[rain_storm]

Im just learnin the ropes still in my first 1/2 year of assembler but I have picked up a lot relevent to graphics n stuff this place is full of great coders and Im glad to see other ways to skin a cat

[mike_g]

Yeah I'd like to have a go at learning assembler some time, just a matter of getting round to it. Anyway, keep it up guys