C_动态分配内存：malloc,realloc,calloc,free

程序控制内存大小随着需求改变：

void main(void)                 /*主函数*/{    int a,b,i,*p,n = 0;    p = (int*)malloc(sizeof(int));    printf("请任意输入两个整数，以空格作为间隔：\t");    scanf("%d %d",&a,&b);    if (a < b)    {        a = a^b;        b = a^b;        a = a^b;    }    if (NULL != p)    {        for (i = a; i <= b; i++)        {            if (check_prime(i))            {                p[n] = i;                n++;                p = (int*)realloc(p,(n + 1)*sizeof(int));  //重新分配内存                if (NULL == p)                {                    printf("内存分配失败");                    break;                }            }        }    }    printf("\n\n%d--%d之间所有的质数有：\n",a,b);    for (i = 0; i < n; i++)    {        printf("%-5d", p[i]);    }    free(p);    system("pause");}