Implementing the Spigot algorithm for π (pi)

Question

I\'m having a hard time understanding the Spigot algorithm for π (pi) found here at the bottom of the page.

I\'m getting lost at the bottom of part 2 \"Put A

Answer 1

I am seeing a difference in the o/p digits of the above spigot pi program when compared with http://www.numberworld.org/misc_runs/pi-10t/details.html

Correct Value of 50 digits of Pi : http://www.numberworld.org/misc_runs/pi-10t/details.html

3.

1415926535 8979323846 2643383279 5028841971 6939937510

Above spigot pi :

3.

1415926535 8979323846 2643383279 5**(0)**28841971 6939937510

                                     ^^^ zero missing

Changed the 4 digits per loop to 8 digits by modifying long f = 100000000;

produced the correct result.