验证哥德巴赫猜想-C

/*
 * @author: Shang
 * @version: 0.01
 * @date: 2011/08/11
 * @src: C语言精彩编程百例（温海 张友 童伟 等编著，中国水利水电出版社）
 * @env: RHEL 5, gcc (GCC) 3.4.6 20060404
 * @status: successful
 * @description: Break an integer into two parts. If both of the two parts are 
 *               prime and their sum is equal to the inputed integer, then print 
 *               integer = part1 + part2. 
 *
 * @result:
$ gcc Goldbach.c -std=c99 -lm
$ ./a.out
Input a positive and even integer: 39
The inputed integer is not right. Please try again: 28
28 = 5 + 23.
 *
 * @history:
 *      1. date: 2011/08/11
 *         author: shang 
 *         modification: Review the book
 */

#include <stdio.h>
#include <math.h>
#include <stdbool.h>

bool isPrime(int num);

int main()
{
    int num = 1;
    
    printf("Input a positive and even integer: ");
    while(((num % 2) != 0) || num < 4)
    {
        if(num != 1)
            printf("The inputed integer is not right. Please try again: ");
		
        scanf("%d", &num);
    }

    for(int part1 = 2; part1 <= num / 2; part1++)
    {
        int part2 = num - part1;

        if(isPrime(part1) && isPrime(part2))
        {
            printf("%d = %d + %d.\n", num, part1, part2);
            break;
        }
    }
}

bool isPrime(int num)
{
    for(int i = 2; i <= (int) sqrt(num); i++)
        if(num % i == 0)
            return false;

    return true;
}