XPost: comp.os.msdos.programmer, alt.lang.asm   
   From: admin@nospicedham.127.0.0.1   
      
   On Fri, 27 Jan 2023 09:57:22 +0000   
   "Kerr-Mudd, John"  wrote:   
      
   > On Wed, 25 Jan 2023 17:02:43 +0000   
   > "Kerr-Mudd, John"  wrote:   
   >   
   []   
   > > > Kerr-Mudd, John wrote:   
   > > > > Finally, a rot13 program for DOS that's smaller than the standard   
   version   
   > > > > with jumps:   
   > > > >   
   > >   
   > > simpler? version; hardcoded IOAREA, rotamt in dl   
   > > ->u 100 l2E   
   > > 1637:0100 BA 0D 1A       mov          dx,1A0D   
   > > 1637:0103 B4 3F          mov          ah,3F   
   > > 1637:0105 89 C1          mov          cx,ax   
   >   
   > Nasty hack gave poor use of seg for R/W buffer; replace with   
   >                            mov ch,E4 ;  (ie. FF-1A-1)   
   > []   
   []   
   'Better' still use C3 (embedded 'ret') to reduce prog to 45 bytes.   
      
   ->u 100 l2D   
   1637:0100 BA 0D 1A       mov          dx,1A0D   
   1637:0103 B4 3F          mov          ah,3F   
   1637:0105 B5 C3          mov          ch,C3   
   1637:0107 CD 21          int          21   
   1637:0109 89 D6          mov          si,dx   
   1637:010B 91             xchg         ax,cx   
   1637:010C E3 F8          jcxzw        0106   
   1637:010E 51             push         cx   
   1637:010F AC             lodsb   
   1637:0110 24 DF          and          al,DF   
   1637:0112 2C 41          sub          al,41   
   1637:0114 38 D0          cmp          al,dl   
   1637:0116 18 E4          sbb          ah,ah   
   1637:0118 38 F0          cmp          al,dh   
   1637:011A D6             salc   
   1637:011B 21 D0          and          ax,dx   
   1637:011D 28 C4          sub          ah,al   
   1637:011F 00 64 FF       add          [si-01],ah   
   1637:0122 E2 EB          loopw        010F   
   1637:0124 59             pop          cx   
   1637:0125 43             inc          bx   
   1637:0126 B4 40          mov          ah,40   
   1637:0128 CD 21          int          21   
   1637:012A 4B             dec          bx   
   1637:012B EB D6          jmp          0103   
   ->          d 100 l2D   
   1637:0100 BA 0D 1A B4-3F B5 C3 CD-21 89 D6 91-E3 F8 51 AC  ....?...!.....Q.   
   1637:0110 24 DF 2C 41-38 D0 18 E4-38 F0 D6 21-D0 28 C4 00  $.,A8...8..!.(..   
   1637:0120 64-FF E2 EB 59-43 B4 40 CD-21 4B EB D6           d...YC.@.!K..   
   ->          q   
      
   --   
   Bah, and indeed Humbug.   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)