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    <td><strong>Decimal Base 10 numbers. </strong></td>
    <td>Count and do arithmetic with ten symbols. [ 0 1 2 3 4 5 6 7 8 9 ]</td>
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    <td><strong>Digital Electronic </strong></td>
    <td>Systems that use binary. Computers use binary numbers and are digital. 
      HiFi systems do not use binary and are not digital. (A HiFi remote control 
      system is digital) See analogue.</td>
  </tr>
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    <td><strong>Directory or Folder </str