title: What are the sizes of tword, oword and yword operands?
body: <p>What are the sizes of <code>tword</code>, <code>oword</code> and <code>yword</code> operands, as used in the <a href="http://www.nasm.us/doc/nasmdoc3.html" rel="noreferrer">NASM</a>/<a href="http://www.tortall.net/projects/yasm/manual/html/manual.html" rel="noreferrer">YASM manual</a>? And on a related note, is there a trick or underlying idea to these names? Is there a way by which bigger word sizes are given logical names?</p>
  
  <p>I know that while word sizes may differ between systems, a NASM <code>word</code> is 2 bytes, <code>dword</code> is double that (4 bytes), <code>qword</code> is a quad word (8 bytes), but... is <code>tword</code> a <em>triple word</em> (6 bytes)? And for <code>oword</code> and <code>yword</code> I can't even think of a plausible meaning.</p>
  
  <p>Note that it is probably an easy question, but I couldn't find an answer. In the NASM and YASM manuals these sizes are not explained, not even at the <code>DQ</code>, <code>DT</code>, <code>DY</code>, <code>RESQ</code>, <code>REST</code>, <code>RESY</code> pseudo-instructions. I read somewhere that MASM uses a similar system, but could not find anything on that either.</p>
  
  <hr>
  
  <p>Edit: Based on the answers, this is the complete list:</p>
  
  <ul>
  <li>1 byte (8 bit): <code>byte</code>, <code>DB</code>, <code>RESB</code></li>
  <li>2 bytes (16 bit): <code>word</code>, <code>DW</code>, <code>RESW</code></li>
  <li>4 bytes (32 bit): <code>dword</code>, <code>DD</code>, <code>RESD</code></li>
  <li>8 bytes (64 bit): <code>qword</code>, <code>DQ</code>, <code>RESQ</code></li>
  <li>10 bytes (80 bit): <code>tword</code>, <code>DT</code>, <code>REST</code></li>
  <li>16 bytes (128 bit): <code>oword</code>, <code>DO</code>, <code>RESO</code>, <code>DDQ</code>, <code>RESDQ</code></li>
  <li>32 bytes (256 bit): <code>yword</code>, <code>DY</code>, <code>RESY</code></li>
  <li>64 bytes (512 bit): <code>zword</code>, <code>DZ</code>, <code>RESZ</code></li>
  </ul>