#include <stdio.h>
#include <stdlib.h>
void main()
{
    int guess,magic;
    magic = rand(); //rand()这是一个取伪随机数的随机函数，srand是取真随机数的函数。
    printf("please enter a guess number:\n");
    scanf("%d",&guess);
    if (guess==magic)
        printf("Gratulation! You Are Right.\n");
    else
        printf("Sorry, You Are Wrong.\n");
}

你的系统居然支持void main()

伪随机数，srand是取种，rand()是取数。