Write functions that :

• reads and return a positive integer
• checks whether an integer is prime or not
• generates the first N primes numbers
• generates the prime factors of an integer

#include<stdio.h>
#include<conio.h>
#include<math.h>
#define N 100

int isprime(int nb)
{
	int i;
	for (i = 2; i <= sqrt(nb); i++)
		if (nb%i == 0)
			return 0;
	return 1;
}
int read()
{
	int n;
	do {
		printf("Enter a nb: ");
		scanf("%d", &n);
	} while (n <= 1);

	return n;
}

void listofprimes(int A[])
{
	int i, count;
	count = 0;
	i = 2;
	while (count < N)
	{
		if (isprime(i))
		{
			A[count] = i;
			//printf("%d ", i);
			count++;
		}
		i++;
	}
}

void print_array(int a[], int S)
{
	int i;
	for (i = 0; i < S; i++)
		printf(" %d \t %d \n", i, a[i]);
	printf("\n\n\n");
}

void print_array2(int a[], int b[], int S)
{
	int i;
	for (i = 0; i < S - 1; i++)
	{
		if (b[i] > 1)
			printf(" %d ^ %d x", a[i], b[i]);
		else
			printf(" %d x", a[i]);
	}
	if (b[i]>1)
		printf(" %d ^ %d.", a[i], b[i]);
	else
		printf(" %d.", a[i]);

	printf("\n\n\n");
}


int prime_factors(int nb, int primes[], int factors[])
{
	int counterinprime = 0, nbfactor = 0;
	while (nb > 1)
	{
		if (nb%primes[counterinprime] == 0)
		{
			factors[nbfactor] = primes[counterinprime];
			nbfactor++;
			nb = nb / primes[counterinprime];
			counterinprime = 0;
		}
		else
			counterinprime++;
	}
	return nbfactor;
}

int pm(int f[], int sf, int dist[], int occ[])
{
	int i, j;
	int count;
	dist[0] = f[0];
	occ[0] = 1;
	count = 1;
	for (i = 1; i < sf; i++)
	{
		for (j = 0; j < count; j++)
		{
			if (f[i] == dist[j])
			{
				occ[j]++;
				break;
			}
		}
		if (j == count)
		{
			dist[j] = f[i];
			occ[j] = 1;
			count++;
		}
	}
	return count;
}

void main()
{
	int nb;
	int result;
	int primes[N];
	int factors[N], size;
	int dist[N], occ[N], s2;

	nb = read();

	//result = isprime(nb);
	/*if (result != 0)
	printf("%d is prime\n", nb);
	else
	printf("%d is not prime\n", nb);
	*/

	listofprimes(primes);
	//print_array(primes,N);

	size = prime_factors(nb, primes, factors);

	//print_array(factors,size);

	s2 = pm(factors, size, dist, occ);

	printf("%d =", nb);
	print_array2(dist, occ, s2);

	getch();
}