From: mikegonta@nospicedham.gmail.com   
      
   On Tuesday, November 19, 2019 at 3:35:46 AM UTC-5, bilsch01 wrote:   
   > If I understand correctly for: shrd ax,dx,cl   
   > ax gets shifted right, dx provides bits to shift into ax from left.   
   > For a 32-bit number 3ffff in dx:ax   
   > (in binary that's eighteen 1's in a row)   
   > I try the following:   
   >   
   > mov cl,2   
   > mov dx,3   
   > mov ax,0xffff   
   > shrd ax,dx,cl   
   > cmp dx,0   
   > jne error   
   >   
   > I thought dx would be shifted empty but it's not.   
      
   That's right - it's not.   
   The source register (in this case dx) only provides the bits to be shifted   
   into the destination (ax). To obtain the complete 32 bit shift the source also   
   needs to be shifted.   
   [code]   
     shrd ax, dx, cl   
     shr dx, cl   
   [/code]   
      
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   Mike Gonta   
   the-ideom - now you know how to compile   
      
   https://mikegonta.com   
      
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