<div class="content"><p>Stores information about the data stored in an XPRESS Block.</p><table>
 <tbody><tr>
  <th><p><br/>0</p></th>
  <th><p><br/>1</p></th>
  <th><p><br/>2</p></th>
  <th><p><br/>3</p></th>
  <th><p><br/>4</p></th>
  <th><p><br/>5</p></th>
  <th><p><br/>6</p></th>
  <th><p><br/>7</p></th>
  <th><p><br/>8</p></th>
  <th><p><br/>9</p></th>
  <th><p>1<br/>0</p></th>
  <th><p><br/>1</p></th>
  <th><p><br/>2</p></th>
  <th><p><br/>3</p></th>
  <th><p><br/>4</p></th>
  <th><p><br/>5</p></th>
  <th><p><br/>6</p></th>
  <th><p><br/>7</p></th>
  <th><p><br/>8</p></th>
  <th><p><br/>9</p></th>
  <th><p>2<br/>0</p></th>
  <th><p><br/>1</p></th>
  <th><p><br/>2</p></th>
  <th><p><br/>3</p></th>
  <th><p><br/>4</p></th>
  <th><p><br/>5</p></th>
  <th><p><br/>6</p></th>
  <th><p><br/>7</p></th>
  <th><p><br/>8</p></th>
  <th><p><br/>9</p></th>
  <th><p>3<br/>0</p></th>
  <th><p><br/>1</p></th>
 </tr>
 <tr>
  <td colspan="32">
  <p align="center">Block
  Signature</p>
  </td>
 </tr>
 <tr>
  <td colspan="32">
  <p align="center">Block
  Compressed Size</p>
  </td>
 </tr>
 <tr>
  <td colspan="32">
  <p align="center">Block Uncompressed
  Size</p>
  </td>
 </tr>
</tbody></table><p><b>Block Signature (4 bytes): </b>MUST be composed of
the four bytes 0x58, 0x42, 0x4c, and 0x4f (or &#39;X&#39;, &#39;B&#39;, &#39;L&#39;, and &#39;O&#39; in ASCII)
as follows.</p><dl>
<dd>
<table>
 <tbody><tr>
  <th><p><br/>0</p></th>
  <th><p><br/>1</p></th>
  <th><p><br/>2</p></th>
  <th><p><br/>3</p></th>
  <th><p><br/>4</p></th>
  <th><p><br/>5</p></th>
  <th><p><br/>6</p></th>
  <th><p><br/>7</p></th>
  <th><p><br/>8</p></th>
  <th><p><br/>9</p></th>
  <th><p>1<br/>0</p></th>
  <th><p><br/>1</p></th>
  <th><p><br/>2</p></th>
  <th><p><br/>3</p></th>
  <th><p><br/>4</p></th>
  <th><p><br/>5</p></th>
  <th><p><br/>6</p></th>
  <th><p><br/>7</p></th>
  <th><p><br/>8</p></th>
  <th><p><br/>9</p></th>
  <th><p>2<br/>0</p></th>
  <th><p><br/>1</p></th>
  <th><p><br/>2</p></th>
  <th><p><br/>3</p></th>
  <th><p><br/>4</p></th>
  <th><p><br/>5</p></th>
  <th><p><br/>6</p></th>
  <th><p><br/>7</p></th>
  <th><p><br/>8</p></th>
  <th><p><br/>9</p></th>
  <th><p>3<br/>0</p></th>
  <th><p><br/>1</p></th>
 </tr>
 <tr>
  <td colspan="8">
  <p align="center">0x58</p>
  </td>
  <td colspan="8">
  <p align="center">0x42</p>
  </td>
  <td colspan="8">
  <p align="center">0x4c</p>
  </td>
  <td colspan="8">
  <p align="center">0x4f</p>
  </td>
 </tr>
</tbody></table>
</dd></dl><p><b>Block Compressed Size (4 bytes): </b>A 32-bit
unsigned integer specifying the size of the XPRESS Block&#39;s data in bytes,
regardless of whether it is compressed. The value of the <b>Block Compressed
Size</b> field MUST be less than or equal to the value of the <b>Block Uncompressed
Size</b> field and greater than 0.</p><p><b>Block Uncompressed Size (4 bytes): </b>A 32-bit
unsigned integer specifying the size of the XPRESS Block&#39;s data when
uncompressed. The <b>Block Uncompressed Size</b> field MUST be less than or
equal to 8,192 bytes.</p></div>