Annotated some of the source of code that exists here: http://www.firstpr.com.au/dsp/pink-noise/#Voss I've annotated using multiline code blocks that are surrounded with /** and */

pink_number.cc

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

class PinkNumber {
private:
  int max_key;
  int key;
  unsigned int range;
  unsigned int white_values[5];

public:
  PinkNumber(unsigned int range = 128) {
    max_key = 0x1f; // Five bits set
    this->range = range;
    key = 0;

    /**
     * This is the end of the constructor for this PinkNumber object.
     *
     * It fills an array that has five elements (see line 9 of this file)
     * with some values. The values are generated up to a maximum of the
     * range provided. By default, the range is 128, which means the
     * white noise values are set between 0 and (128 / 5).
     */
    for (int i = 0; i < 5; i++) {
      white_values[i] = rand() % (range/5);
    }
  }

  int GetNextValue() {
    int last_key = key;
    unsigned int sum;

    key++;
    if (key > max_key) {
      key = 0;
    }

    // Exclusive-Or previous value with current value. This gives
    // a list of bits that have changed.

    /**
     * XOR is a bit of a difficult thing to get your head around, but the
     * best thing to read is this:
     *  - https://www.cs.umd.edu/class/sum2003/cmsc311/Notes/BitOp/xor.html
     *  - https://en.wikipedia.org/wiki/Exclusive_or
     */
    int diff = last_key ^ key;
    sum = 0;

    for (int i = 0; i < 5; i++) {
      // If bit changed get new random number for corresponding
      // white_value
      if (diff & (1 << i)) {
        white_values[i] = rand() % (range/5);
      }

      sum += white_values[i];
    }

    return sum;
  }
};

int main() {
  PinkNumber pn;

  for (int i = 0; i < 100; i++) {
    std::cout << pn.GetNextValue() << std::endl;
  }

  return 0;
}