title: Why did we add a dot in multiplication in order to run the program?
body: <p>I'm writing a program that calculates the roots of the quadratic equation. When I first wrote the code I didn't type a dot after 4 and 2 in the x equation and it didn't work! So what does that dot represent here and when should I use it?</p>
  
  <pre><code>#include&lt;stdio.h&gt;
  #include&lt;conio.h&gt;
  #include&lt;math.h&gt;
  
  int main()
  {
     int a, b, c;
     double x;
     scanf("%d %d %d", &amp;a, &amp;b, &amp;c); 
  
     x = (-b + sqrt(b*b-4.*a*c) ) / (2.*a);
  
     printf("%lf", x);
     getch();
  
     return 0;
  }
  </code></pre>