Function

test

/* Computes pairwise averages of three numbers */
#include <stdio.h>

double average(double a, double b)
{
    return (a + b) / 2; 
}

int main(void)
{
    double x, y, z;

    printf("Enter three numbers: ");

    scanf("%lf%lf%lf", &x, &y, &z);
    printf("Average of %g and %g: %g\n", x, y, average(x, y));
    printf("Average of %g and %g: %g\n", y, z, average(y, z));
    printf("Average of %g and %g: %g\n", x, z, average(x, z));

    return 0;
}

/* Prints a countdown */
#include <stdio.h>

void print_count(int n)
{
    printf("T minus %d and counting\n", n);
}

int main(void)
{
    int i;

    for(i = 10; i > 0; --i)
        print_count(i);

    return 0;
}

#include <stdio.h>

//void表示没有实际参数；占位符
void print_pun(void)
{
    printf("To C, or not to C: that is the question.\n");
}

int main(void)
{
    //函数没有参数要带上圆扣号
    print_pun();
    return 0;
}

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

//prime:只有1与该数本身两个正因数的数
bool is_prime(int n)
{
    int divisor;

    if(n <= 1)
        return false;
    for (divisor = 2; divisor * divisor <= n; divisor++)
        if(n % divisor == 0)
            return false;
    return true;
}

int main(void)
{
    int n;

    printf("Enter a number: ");
    scanf("%d", &n);
    if(is_prime(n))
        printf("Prime\n");
    else
        printf("Not prime\n");

    return 0;

}