From: nowhere@nospicedham.never.at   
      
   On 21.04.2021 13:12, Kerr-Mudd,John wrote:   
   > On Tue, 20 Apr 2021 14:52:58 GMT, wolfgang kern   
   >  wrote:   
   >   
   >> On 20.04.2021 17:55, Robert Prins wrote:   
   >>> Just came across this one:   
   >>>   
   >>> C4 1C 9F AB 47 47 EB F9   
   >>>   
   >>> Save as a .COM file and run it, even in DOSBox-X. (Do a CLS before   
   >>> you start it)   
   >>>   
   >>> Comparable to a gem like "+[>,]+[<.-]" in that language that usually   
   >>> has an '*' in it's name. ;)   
   >>>   
   >>> Robert   
   >>   
   >> I can't recommend to do this!   
   >>   
   >> endless:   
   >> LES BX,[SI]  ;SI=?? may depend on environment   
   >> LAHF         ;who knows what's in the flags ?   
   >> STOSW        ;WRITE to ES:DI (try to use cc-flags for color)   
   >> INC DI dup2  ;stosw does this also   
   > skips next scrn char   
   >   
   >> JMP $-7      ;endless or until crash   
   >>   
   >> BX isn't used.   
   > except to set es.   
   >   
   >> And if SI doesn't point to the screen-seg it writes to another 64KB   
   >> block.   
      
   > I presume it's meant to put stripes down the screen; but al is 0 at start;   
   > aha! I see the jmp goes to 101, which becomes SBB al,9F   
      
   yeah, I saw it but forgot to mention where AL get its value.   
      
   > I thought a .COM file at startup has bx=0x0000,si=0x0100,di=0xFFFE,   
   > es=ds=cs;   
   > LES must somehow pick up the Screen seg.   
      
   if DS:SI points to CS:0100 then ES:BX read as AB9f:1cc4 which is at the   
   end of in the graphics-RAM range (nothing to see in text mode) but it   
   overwrites part of the VideoBIOS (it may be RAM-mapped and writable).   
      
   > OK it's a mini 'Matrix' tribute. Nice.   
   I cannot try such here.   
   __   
   wolfgang   
      
   --- SoupGate-Win32 v1.05   
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