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#include<stdio.h>
//int main()
//{
//?? ?int a = 0;
//?? ?printf("%d\n", ~a);//答案为-1
//?? ?//~把二进制中的数字，1变0，0变1
//?? ?//00000000000000000000000000000000
//?? ?//~
//?? ?// 在计算机的中储存的是补码
//?? ?//11111111111111111111111111111111原码
//?? ?//10000000000000000000000000000000反码
//?? ?//反码+1=补码
//?? ?//10000000000000000000000000000001补码
//?? ?//即为-1
//?? ?return 0;
//}
//int main()
//{
//?? ?int a = 10;
//?? ?int b = a++;
//?? ?int a2 = 10;
//?? ?int b2 = ++a2;
//?? ?//a++和++a的区别
//?? ?//a++先使用，再++
//?? ?//++a先++，再使用
//?? ?printf("%d\n", a);
//?? ?printf("%d\n", b);
//?? ?printf("%d\n", a2);
//?? ?printf("%d\n", b2);
//?? ?return 0;
//}
//int main()
//{
//?? ?int a = (int)3.14;
//?? ?//这里的（int）为强制类型转化，不推荐使用
//?? ?printf("%d\n", a);
//?? ?return 0;
//}
//&&与
//||或
//int main()
//{
//?? ?int a = 0;
//?? ?int b = 1;
//?? ?int c = a > b ? a : b;
//?? ?printf("%d\n", c);
//?? ?return 0;
//}
//exp?exp1:exp2
//exp成立输出exp1，否则就是exp2
//int main()
//{
//?? ?register int a = 0;
//?? ?//register建议把a=0放在寄存器里面，速度快
//?? ?return 0;
//}
//typedef unsigned int u_int;
//int main()
//{
//?? ?u_int a = 0;
//?? ?return 0;
//}
//typedef类型的重定义
//void test()
//{
//?? ?static int a = 1;
//?? ?//static改变了局部变量的生命周期
//?? ?a++;
//?? ?printf("%d\n", a);
//}
//int main()
//{
//?? ?int i = 1;
//?? ?while (i < 10)
//?? ?{
//?? ??? ?test();
//?? ??? ?i++;
//?? ?}
//?? ?return 0;
//}
extern int g_val;
extern 声明外部符号
static修饰的全局变量，只能在自己所在的源文件使用
//int main()
//{
//?? ?printf("%d\n", g_val);
//?? ?return 0;
//}
//define定义宏
//#define ADD(X,Y) ((X)+(Y))
//int main()
//{
//?? ?printf("%d\n", 4 * ADD(3, 4));
//?? ?return 0;
//}
//int main()
//{
//?? ?int a = 10;
//?? ?printf("%p\n", &a);//%p打印十六位，&取地址
//?? ?int* pa = &a;//*说明pa是指针变量
//?? ?char ch = 'w';
//?? ?char* pch = &ch;
//?? ?printf("%p\n", pch);
//?? ?return 0;
//
//}
//int main()
//{
//?? ?int a = 10;
//?? ?int* pa = &a;
//?? ?*pa = 20;
//?? ?printf("%d\n", a);
//?? ?return 0;
//}//通过a的地址pa来改变a
//int main()
//{
//?? ?printf("%d\n", sizeof(char*));
//?? ?printf("%d\n", sizeof(short*));
//?? ?printf("%d\n", sizeof(int*));
//?? ?printf("%d\n", sizeof(long*));
//?? ?printf("%d\n", sizeof(long long*));
//?? ?printf("%d\n", sizeof(float*));
//?? ?printf("%d\n", sizeof(double*));
//?? ?return 0;
//}//指针大小都是一样的，只和操作系统有关系
struct stu
{
?? ?char name[20];
?? ?int age;
?? ?int score;
};
int main()
{
?? ?struct stu s=
?? ?{
?? ??? ?"张三",20,90
?? ?};
?? ?struct stu* ps = &s;
?? ?printf("1:%s %d %d\n", s.name, s.age, s.score);//结构体的创建和初始化
?? ?printf("2:%s %d %d\n", (*ps).name, (*ps).age, (*ps).score);
?? ?printf("3:%s %d %d\n", ps->name, ps->age, ps->score);
?? ?return 0;
}
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