Mandelbrot Set calculation with complex.h

mandelbrot.c

#include <stdio.h>
#include <complex.h>

int main(void)
{
    double xl = -2.0;
    double xu = 0.5;
    double yl = -1.1;
    double yu = 1.1;

    int reps = 20;

    int width = 40;
    int height = 25;

    double xinc = (xu - xl) / width;
    double yinc = (yu - yl) / height;

    for (int j = 0; j < height; j++)
    {
        for (int i = 0; i < width; i++)
        {

            double nreal = xl + i * xinc;
            double nimg = yl + j * yinc;
            double complex c = nreal + nimg * I;
            double complex z = 0 + 0 * I;
            char out = ' ';

            for (int k = 1; k <= reps; k++)
            {
                z = cpow(z, 2) + c;
                if (cabs(z) > 2.0)
                {
                    out = 'A' + (k / 2);
                    break;
                }
            }
            printf("%c", out);
        }
        printf("\n");
    }
}