title: How many bytes is a gigabyte (GB)?
body: <p>When I convert between 1GB to byte using online tools, I get different answers. For instance, using Google Convertor: <code>1GB=1e+9</code> while in another converter I get <code>1GB= 1073741824</code>. I suppose the unit is used in different fashion based on whether <code>1KB=1024B</code> or <code>1KB=1000B</code> (this is Google unit). </p>
  
  <p>How can I know which unit my machine uses using a small C program or function? Does C have a macro for that? I want to do that as my program will possibly be run via various operating systems.</p>