title: Making large constants in C source more readable?
body: <p>I'm working on some code for a microprocessor.<br>
  It has a few large, critical constants.</p>
  
  <p><code>#define F_CPU 16000000UL</code></p>
  
  <p>In this case, this is the CPU frequency. In Hertz.</p>
  
  <p>As it is, it's rather hard to tell if that's 1,600,000, 160,000,000 or 16,000,000 without manually tabbing a cursor across the digits.</p>
  
  <p>If I put commas in the number <code>#define F_CPU 16,000,000UL</code>, it truncates the constant.</p>
  
  <p>I've worked with a few esoteric languages that have a specific digit-separator character, intended to make large numbers more readable (ex <code>16_000_000</code>, mostly in languages intended for MCUs). Large "magic numbers" are rather common in embedded stuff, as they are needed to describe aspects of how a MCU talks to the real world.</p>
  
  <p>Is there anything like this in C?</p>