Digital Loop Filter

#include <iostream>
#include <stdlib.h>
#include <math.h>


using namespace std;

int main() {
    double b0 = 0.009765625;
    double b1 = 0.01014328003;
    double b2 = -0.009014129639;
    double b3 = -0.009391784668;

    double a1 = -1.641998291;
    double a2 = 0.7047691345;
    double a3 = -0.06273269653;

    int i;
    int iteration = 10;

    double x = 0, y = 0;
    double in_data[10] = {255, 255, 255, 190, 158, 146, 221, 218, 112, 45};


    // for direct form I     
    double y1 = 0, y2 = 0, y3 = 0;
    double x1 = 0, x2 = 0, x3 = 0;
    
    printf("Direct form I\n");
    for(i=0; i<iteration; i++)
    {
        x = in_data[i] - 128;

        y = b0*x + b1*x1 + b2*x2 + b3*x3 - a1*y1 - a2*y2 - a3*y3;
        y = floor(y);

        x3 = x2;
        x2 = x1;
        x1 = x;


        y3 = y2;
        y2 = y1;
        y1 = y;

        printf("The %d interation, x = %lf, y = %lf \n", i, x+128, y+128);
    }

    // for Direct form II Transposed

    printf("\n");
    printf("Direct form II Transposed\n");
    x = 0; y = 0;
    double s1z = 0; 
    double s2z = 0;
    double s3z = 0;
    
    for(i=0; i<iteration; i++)
    {
        x = in_data[i] - 128;
        y = s1z + b0*x;
        
        printf("out_sum = %lf\n", y*pow(2,18));
        
        y = floor(y);
        
        printf("b0*x = %lf\n", b0*x*pow(2,18));
        printf("b1*x = %lf, a1*y = %lf\n", b1*x*pow(2,18), a1*y*pow(2,18));
        printf("b2*x = %lf, a2*y = %lf\n", b2*x*pow(2,18), a2*y*pow(2,18));
        printf("b3*x = %lf, a3*y = %lf\n", b3*x*pow(2,18), a3*y*pow(2,18));
        printf("s1z = %lf  ", s1z*pow(2,18));
        printf("s2z = %lf  ", s2z*pow(2,18));
        printf("s3z = %lf\n", s3z*pow(2,18));
        printf("The %d interation, x = %lf, y = %lf \n", i, x+128, y+128);
        
        s1z = s2z + b1*x - a1*y;
        s2z = s3z + b2*x - a2*y;
        s3z = b3*x - a3*y;
    }

    return 0;
}