Thread: Getting error

Hello, im new in C++ and im getting annoying error. Maybe anyone could explain me where is the problem. Compiler shows that a problem is in a line 20 If (D<0).

Code:

#include <stdio.h>
#include <stdlib.h>
int main ()
{
    float a,b,c,D,x1,x2;
    printf ("Iveskite a kintamaji \n");
    scanf ("%f",a);
    printf ("Iveskite b kintamaji \n");
    scanf ("%f",b);
    printf ("Iveskite c kintamaji");
    scanf ("%f",c);
    if (a=0)
    {
    printf ("Lygtis ne kvadratine, niekas nebus apskaiciuota \n");
    system ("pause");
    return 0;
    }
     else
      D =(b*b) - (4*a*c);
    If (D<0)
     printf ("Sprendiniu nera \n");
    else 
    {
    x1= ((-1)*b-sqrt(D))/(2*a);
     x2= ((-1)*b+sqrt(D))/(2*a);
    Printf ("Atsakymai: %f, %f \n",x1,x2);
    system ("pause");
    return 0;
    }
}

This is C, not C++.