What is number at the beginning of a binary digit?
<p>I've seen various binary numbers like 0x00 0x0F, but I've never seen a binary number like 1x90. Lets demonstrate a binary number as AxBC. A is always the same. It doesn't differ. I've found a forum about this, but they say it is constant.
<a href="http://www.avrfreaks.net/forum/0x00-0x01-0x02-nxnn" rel="nofollow">http://www.avrfreaks.net/forum/0x00-0x01-0x02-nxnn</a>
I couldn't  find any answer because people usually emphasize the right part rather than the left part.</p>

<p>I wonder what it stands for and why we use it. If it is a constant why do we use it? Is it just an identifier?</p>

<p>Thanks...</p>