title: Type of formal parameter 1 is incomplete
body: <p>I'm trying to write a program that adds two rational numbers with structures 
  and this is the code</p>
  
  <pre><code>#include &lt;stdio.h&gt;
  #include &lt;stdlib.h&gt;
  
  struct Fraction{
                  int numerator ;
                  int denominator ;
                  };
  
  int mainMenu(void);
  struct Fraction readStructure(void); /*this works well*/
  struct Fraction add(struct Fractoin num1, struct Fraction num2);/*this doesn't*/
  
  int main()
  {
      struct Fraction num1 = readStructure();
      struct Fraction num2 = readStructure();
  
      struct Fraction result = add(num1, num2) ;
  
      return 0 ;
  }
  struct Fraction readStructure(void)
  {
      struct Fraction temp;
  
      printf("-&gt; Enter the numerator : ");
      scanf("%d", &amp;temp.numerator);
      printf("-&gt; Enter the denominator : ");
      scanf("%d", &amp;temp.denominator);
      while(temp.denominator == 0)
      {
          printf("--&gt; Zero in the denominator isn't possible.. try again : ");
          scanf("%d", &amp;temp.denominator);
      }
  
      return temp ;
  }
  struct Fraction add(struct Fractoin num1, struct Fraction num2)
  {
      struct Fraction temp;
  
      temp.numerator = (num1.numerator * num2.denominator) +
                       (num2.numerator * num1.denominator);
      temp.denominator = num1.denominator * num2.denominator ;
  
      return temp ;
  }
  </code></pre>
  
  <p>the compiler says it's wrong and gives me those errors + some more warnings..</p>
  
  <pre><code>error: type of formal parameter 1 is incomplete.
  error: parameter 1 ('num1') has incomplete type.
  </code></pre>