title: How to write log base(2) in c/c++
body: <p>Is there any way to write log(base 2) function?</p>
  
  <p>The  C language has 2 built in function -->></p>
  
  <p>1.<code>log</code> which is base e.</p>
  
  <p>2.<code>log10</code> base 10;</p>
  
  <p>But I need log function of base 2.How to calculate this.</p>