title: Type of formal parameter 1 is incomplete error
body: <p>I'm trying to write a program that print information of a student 
  but Code::Blocks says : </p>
  
  <p>error : Type of formal parameter 1 is incomplete.
  error : conflicting types for 'displayStudentInformation'
  and this is the code.</p>
  
  <pre><code>#include &lt;stdio.h&gt;
  
  void displayStudentInformation(struct student stu);
  
  struct student{
    int id;
    char *firstName;
    char *lastName;
    float gpa;
  };
  
  int main()
  {
    struct student stu1;
    stu1.id = 101;
    stu1.firstName = "Ali";
    stu1.lastName = "Alavi";
    stu1.gpa = 18;
  
    displayStudentInformation(stu1);
  
    return 0;
  }
  
  void displayStudentInformation(struct student stu)
  {
    printf("Student information :\n");
    printf("ID : %d",stu.id);
    printf("First Name : %s",stu.firstName);
    printf("Last Name :%s",stu.lastName);
    printf("GPA : %.2f",stu.gpa);
    printf("\n");
  }
  </code></pre>