BIOS TeleType putc/puts trick...

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bitshifter

Joined: 04 Dec 2007
Posts: 796
Location: Massachusetts, USA

bitshifter 26 Jun 2010, 01:37

I made putc and puts functionality in 14 bytes today Razz

Code:

puts:   ; DS:SI -> string to print
        lodsb   ; ASSUME: DF = 0
        test    al,al
        jz      putc.ret
        push    puts
putc:   ; AL = character to print
        mov     ah,0eh
        xor     bh,bh
        int     10h
  .ret: ret

Very useful when size matters...

_________________
Coding a 3D game engine with fasm is like trying to eat an elephant,
you just have to keep focused and take it one 'byte' at a time.

26 Jun 2010, 01:37

LocoDelAssembly
Your code has a bug

Joined: 06 May 2005
Posts: 4624
Location: Argentina

LocoDelAssembly 26 Jun 2010, 02:12

hehe, good one. Very Happy

26 Jun 2010, 02:12

Tyler

Joined: 19 Nov 2009
Posts: 1216
Location: NC, USA

Tyler 26 Jun 2010, 04:42

Size matters... Wink

26 Jun 2010, 04:42

ManOfSteel

Joined: 02 Feb 2005
Posts: 1154

ManOfSteel 26 Jun 2010, 08:14

Push/ret! Nice trick.

26 Jun 2010, 08:14

Picnic

Joined: 05 May 2007
Posts: 1398
Location: Piraeus, Greece

Picnic 26 Jun 2010, 13:55

Nice trick bitshifter.
Goes down to 10 bytes if undocumented INT 29H is used Smile

26 Jun 2010, 13:55

Teehee

Joined: 05 Aug 2009
Posts: 570
Location: Brazil

Teehee 26 Jun 2010, 14:08

'undocumented INT 29H', whats that? Surprised

26 Jun 2010, 14:08

Picnic

Joined: 05 May 2007
Posts: 1398
Location: Piraeus, Greece

Picnic 26 Jun 2010, 14:30

INTERRUPT 29h will write the char in AL to the screen faster than service 02h or 09h of int 21h though is identical (not counting redirection) to service 02h of int 21h (but much faster).

http://www.fysnet.net/undoc.htm

Code:

puts:   ; DS:SI -> string to print
        lodsb   ; ASSUME: DF = 0
        test    al,al
        jz      putc.ret
        push    puts
putc:   ; AL = character to print
        int 29h
  .ret: ret

26 Jun 2010, 14:30

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