title: C preprocessor #if expression
body: <p>I am a bit confused on the type of expression we can use with the #IF preprocessor in the C language. I tried the following code, and it isn't working. Please explain and provide examples for expressions that can be used with the preprocessor.</p>
  
  <pre><code>#include&lt;stdio.h&gt;
  #include&lt;conio.h&gt;
  #include&lt;stdlib.h&gt;
  
  int c=1;
  
  #if c==1
      #define check(a) (a==1)?a:5
      #define TABLE_SIZE 100
  #endif
  
  int main()
  {
      int a = 0, b;
      printf("a = %d\n", a);
      b = check(a);
      printf("a = %d %d\n", a, TABLE_SIZE);
      system("PAUSE");
      return 0;
  }
  </code></pre>