C语言各种操作符透彻理解下篇

#include<stdio.h>
int main()
{
	//sizeof
	int a = 10;
	printf("%d\n", sizeof(a));
	printf("%d\n", sizeof(int));
	printf("%d\n", sizeof(float));
	printf("%d\n", sizeof(double));
 
	int arr[10] = { 1,2,3,4,5,6,7 };
	printf("%d\n", sizeof(arr));
	printf("%d\n", sizeof(int[10]));//计算整个数组的长度
 
	printf("%d\n", sizeof a);
	//printf("%d\n", sizeof int);这样写是会报错的
 
 
	return 0;
}

#include<stdio.h>
int main()
{
    int a = 0;
	//~按（内存中补码的2进制）位取反
	//00000000000000000000000000000000
	//11111111111111111111111111111111 - 补码
	//11111111111111111111111111111110 - 反码
	//10000000000000000000000000000001 - 原码 --> -1
 
	printf("%d\n", ~a);
 
	return 0;
}

#include<stdio.h>
int main()
{
    int a = 10;
	a |= (1 << 2);
	printf("%d\n", a);
	a &= ~(1 << 2);
	printf("%d\n", a);
    return 0;
 
	//如果只想把倒数第三个数，也就是0改为1，可以进行以下操作
	//00000000000000000000000000001010
	//00000000000000000000000000000100   1<<2(用a与1<<2异或来实现）
	//00000000000000000000000000001110
	//11111111111111111111111111111011   ~(1<<2)(要想将a复原，就是再将倒数第三个数变为0）
	//00000000000000000000000000001010
}

#include<stdio.h>
int main()
{
    int a = 10;
	int* pa = &a;
	*pa = 20;//通过*来访问a的地址
	printf("%d\n", a);
	printf("%d\n", *pa);//此时的*pa就是a的值
 
	int* px = &*pa;//px通过*来访问*pa,也就是访问a
	*px = 30;
	printf("%d\n", a);
    return 0;
}

#include<stdio.h>
int main()
{
    int a = 10;
	int b = 20;
	int max = 0;
	
 
	max = (a > b ? a : b);//与上面那段代码等价
    return 0;
}

    int a = 1;
	int b = 2;
	int c = (a > b, a = b + 10, a, b = a + 1);

#include<stdio.h>
 
void menu()
{
    printf("*************************\n");
	printf("******    hello    ******\n");
	printf("******   friends   ******\n");
	printf("*************************\n");
}
 
int main()
{
    menu();
    return 0;
}

#include<stdio.h>
 
struct Stu
{
    char name[10];
    int age;
    double score;
};
 
int main()
{
    struct Stu s = { "zhangsan",20,85.5 };
	//.
	printf("%s %d %.1lf\n", s.name, s.age, s.score);
	//->
	struct Stu* ps = &s;
	printf("%s %d %.1lf\n", (*ps).name, (*ps).age, (*ps).score);
	printf("%s %d %.1lf\n", ps->name, ps->age, ps->score);
    return 0;
}

#include<stdio.h>
int main()
{
    short s = 20;
	int a = 5;
	printf("%d\n", sizeof(s = a + 4));
	printf("%d\n", s);
    return 0;
}

// 代码 3- 非法表达式
int main ()
{
int i = 10 ;
i = i -- - -- i * ( i = - 3 ) * i ++ + ++ i ;
printf ( "i = %d\n" , i );
return 0 ;
}