title: Why is BCD = Decimal in PLC?
body: <p>This question is derived from <a href="https://stackoverflow.com/questions/9327806/what-does-the-sign-mean-omron-plc">my previous SO question's commends</a>. </p>
  
  <p>I am confused with PLC's interpretation of BCD and decimal. 
  In a PLC documentation, it somehow implies BCD = decimal:</p>
  
  <p><img src="https://i.stack.imgur.com/o3WHR.png" alt="enter image description here"></p>
  
  <p>The instruction reads the content of D300, 0100, as BCD.  Referring to <a href="https://stackoverflow.com/questions/4494664/binary-coded-decimal-bcd-to-hexadecimal-conversion">Cyber Slueth Omega's answer</a> and <a href="http://www.miniwebtool.com/bcd-to-hex-converter/" rel="nofollow noreferrer">online BCD-Hex converter</a>, 0100 (BCD) = 4 (Decimal) = 4 (Hex), but the documentation indicates 0100 (BCD) = 100 (Decimal). </p>
  
  <p>Why?</p>