title: C negation in if-statement?
body: <p>I am examining a C code for a pressed key in a embedded system.</p>
  
  <p>In the code below you can see an if-statement with ! before checking REG8, what does this mean in a situation like this? I am just asking about the character (!) and not what the code does.</p>
  
  <pre><code>if(!(REG8(DataRegA) &amp; 0x80)){ 
  *key=REG8(DataRegA) &amp; 0x0F;
  return(1); 
  }
  </code></pre>