7月16日 --指针

#define _CRT_SECURE_NO_WARNINGS 1
#include <stdio.h>
#include <string.h>




struct stu
{
	char name[20];
	int age;
	char id[20];
};

int main()
{
	int a = 0;
	struct stu s1 = { "张三", 20, "775513640" };
	struct stu* ps = &s1;
	printf("%s\n", ps->name);
	printf("%d\n", ps->age);
	/*printf("%s\n", (*ps).name);
	printf("%d\n", (*ps).age);*/
	return 0;
}











int main()
{
	char a = 3;
	//00000000000000000000000000000011
	//00000011 -- a
	char b = 127;
	//00000000000000000000000001111111
	//01111111 -- b
	char c = a + b;
	//a+b
	//00000011 -- a
	//01111111 -- b
	//10000010 -- c
	printf("%d\n", c);
	return 0;
}










int main()
{
	int a = 10;
	int b = 20;
	int c = a + a * 3;

	return 0; 
}










int main()
{
	int a = 0x11223344;
	int* pa = &a;
	//*pa = 0;
	char* pc = &a;
	//指针类型决定了指针进行解引用操作的时候，能够访问空间的大小
	//int*p; *p能够访问4个字节
	//char*p; *p能够访问1个字节
	//double*p; *p能够访问8个字节
	//*pc = 0;
	/*指针类型决定了：指针一步走多远（指针的步长）
	int *p; p+1-->4
	char *p; p+1-->1
	double*p; p+1-->8
	*/
	printf("%p\n", pa);
	printf("%p\n", pa+1);
	printf("%p\n", pc);
	printf("%p\n", pc+1);
	return 0;
}











int main()
{
	int arr[10] = { 0 };
	char* p = &arr;
	int i = 0;
	for (i = 0; i < 10; i++)
	{
		*(p + i) = 1;
	}
	return 0;
}









int mian()
{
	//int a;//局部变量不初始化，默认是随机值
	int*p;//局部的指针变量，就被初始化随机值
	*p = 20;
	return 0;
}








int main()
{
	int arr[10] = { 0 };
	int *p = arr;
	int i = 0;
	for (i = 0; i < 12; i++)
	{
		p++;
	}
	return 0;
}










test()
{
	int a = 10;
	return &a;
}
int main()
{
	int *p = test();
	*p = 20;
	return 0;
}













int main()
{
	int* p;
	*p = 20;
	return 0;
}









int main()
{
	int a[10] = { 0 };
	int i = 0;
	int* p = a;
	for (i = 0; i <= 12; i++)
	{
		//*p = 1;
		//p++;
		*p++ = i;
	}

	return 0;
}










int* test()
{
	/*int a = 10;
	return &a;*/
	int arr[10] = { 0 };
}

int main()
{
	int *p = test();
	printf("%d\n", *p);
	return 0;
}








int main()
{
	int a = 10;
	int *pa = &a;
	*pa = 20;
	//int* p = NULL;//NULL--  ((void *)0)用来初始化指针，给指针赋值
	*pa = 10;
	pa = NULL;
	if (pa != NULL)
	{
		*pa = 20;
	}
	return 0;
}










int main()
{
	int arr[10] = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 };
	int i = 0;
	int sz = sizeof arr / sizeof (arr[0]);
	int* p = &arr[9];
	/*for (i = 0; i < sz; i++)
	{
		printf("%d", *p);
		p++;
	}*/
	for (i = 0; i < 5; i++)
	{
		printf("%d ", *p);
		p -= 2;
	}
	return 0;
}