question 3

/*
Lab exam winter semester 2016/2017.
Lecture: IE-B1-SO1 (Software construction 1)
Student: Daniel Dedoukh
*/

#define _CRT_SECURE_NO_DEPRECATE
#include <stdio.h>
#include <math.h>
#define DIM 2

// Define boolean
typedef enum
{
	FALSE = 0, // no need to set value to 0, but it's better for understanding
	TRUE = 1
}boolean;

/* Function prototypes */
int isEven(int);
boolean isPrimeNumber(int);

int main(void)
{
	int num;
	int count = 0;

	// Get user input
	printf("Enter maximum number to test ( positive integer number ) : ");

	while ((scanf("%d", &num) != 1) || (num < 1))
	{
		printf("Invalid input, must be positive integer. Retry: ");
		while (getchar() != '\n')
			continue;
	}

	while (getchar() != '\n')
		continue;

	// Print prime numbers
	printf("Prime numbers in [1, %d]: \n", num);

	for (int i = 0; i <= num; i++)
	{
		if (isPrimeNumber(i) == TRUE)
		{
			printf("%3d ", i);
			count++;

			if ((count % 10) == 0)
				putchar('\n');
		}
	}

	printf("\nThere are %d prime numbers in [1, %d]: \n", count, num);

	getchar();
	return 0;
}

int isEven(int a)
{
	/* Test even numbers */
	if ((a % 2) == 0)
		return TRUE; // if number is even return TRUE

	else if ((a % 2) != 0)
		return FALSE; // if number is not even return FALSE

	return 0;
}

boolean isPrimeNumber(int a)
{
		if (a <= 1)
			return FALSE;

		/* Test even numbers */
		if ((isEven(a) == TRUE) && (a >= 4))
			return FALSE;

		/* Test odd numbers */
		for (int i = 3; i < a / 2; i += 2)
		{
			if ((a % i) == 0)
				return FALSE;
		}
		return TRUE;
}