title: what does mean instruction like mov byte ptr [rax + rdx-1], 00 with such offset where rax not pointer
body: <p>Stuck with study of assembler </p>
  
  <pre><code>mov byte ptr [rax+rdx-01],00
  
  RAX=00000004
  RDX=2295EA3B878
  </code></pre>
  
  <p>and </p>
  
  <pre><code>mov [r10+rsi],al
  
  RAX=0000000000000065
  RSI=000002295EA3B878
  R10=0000000000000000
  </code></pre>
  
  <p>It's clear about <code>mov</code> <code>al</code> <code>byte ptr</code>. But i don't understand  what means  <code>[rax+rdx-01]</code> and <code>[r10+rsi]</code>  where rax and r10 not pointer.</p>
  
  <p>In most cases i faced with <code>[RAX+C1]</code> where rax is pointer and C1 is offset but i have no idea what meaning when register store some value, but not a pointer  </p>