Prime factors and their applications

#include 

int PrimeFactors(int n, int *factors) {
  int count, i;

  count = 0;
  for (i = 2; i <= n; i++) {
    while (n % i == 0) {
      /* find a prime factor, add it into the array */
      factors[count] = i;
      count ++;
      n = n / i;
    }
  }

  return count;
}

#define MAX_ARRAY_SIZE 100

int main() { /* test program */
  int numFactors, i;
  int factors[MAX_ARRAY_SIZE];

  printf("Factors of 567: ");
  numFactors = PrimeFactors(567, factors);
  for (i = 0; i < numFactors; i++) {
    printf("%d ", factors[i]);
  }

  printf("\nFactors of 5678901: ");
  numFactors = PrimeFactors(5678901, factors);
  for (i = 0; i < numFactors; i++) {
    printf("%d ", factors[i]);
  }
  printf("\n");

  return 0;
}

#include 

void Emphasise(char *word) {
  int i, j, flag;

  flag = 0; /* to mark whether it is between the two underscores */
  for (i = 0, j = 0; word[i] != '\0'; i++) {
    char c = word[i];
    if (c == '_') {
      flag = 1 - flag;
    } else {
      if (flag == 1 && c >= 'a' && c <= 'z') {
        /* find a lowercase letter between two underscores,
         * turn it into uppercase */
        c = c - 'a' + 'A';
      }
      /* save back to the word */
      word[j] = c;
      j ++;
    }
  }
  word[j] = '\0';
}

#define MAX_ARRAY_SIZE 100

int main() { /* test program */
  char wordsA[MAX_ARRAY_SIZE] = "this is a _good_ question!";
  char wordsB[MAX_ARRAY_SIZE] = "It is _over 9000_!";
  char wordsC[MAX_ARRAY_SIZE] = "_Nothing to see here_";

  Emphasise(wordsA);
  Emphasise(wordsB);
  Emphasise(wordsC);

  printf("%s\n", wordsA);
  printf("%s\n", wordsB);
  printf("%s\n", wordsC);

  return 0;
}