指针由浅入深

1.变量与地址
2.指针与指针变量
3.直接访问和间接访问
4.空指针与野指针
5.空类型
6.定义与初始化的书写规则
7.指针运算
8.指针与数组
指针与一维数组
指针与二维数组
指针与字符数组
9.const与指针
10.指针数组和数组指针
11.多级指针

#include<stdio.h>
#include<stdlib.h>
int main()
{int i = 1;int *p;p = &i;//int *p = &i;  *是跟着int走的，类型是 int *  名字叫p（合法的标识符）float *q;double *d;char *c;printf("%d\n",sizeof(p));printf("%d\n",sizeof(q));printf("%d\n",sizeof(d));printf("%d\n",sizeof(c));//指针在某个平台下占用的大小是确定的
#if 0printf("%d\n",sizeof(i));printf("%d\n",sizeof(p));printf("i = %d\n",i);printf("&i = %p\n",&i);printf("p = %p\n",p);printf("&p = %p\n",&p);printf("*p = %d\n",*p);
#endifexit(0);
}

野指针

#include<stdio.h>
#include<stdlib.h>
int main()
{int *p = NULL;//空指针void *q = NULL;//void 类型的指针 不确定现在需要什么类型的指针exit(0);
}

#include<stdio.h>
#include<stdlib.h>
int main()
{int i = 1;//空指针int *p = &i;//void 类型的指针 不确定现在需要什么类型的指针int **q = &p;
// i *p **p
//&i  p  *qprintf("i = %d\n",i);printf("&i = %p\n",&i);printf("p = %p\n",p);printf("&p = %p\n",&p);printf("*p = %d\n",*p);printf(" q= %p\n",q);printf("*q = %p\n",*q);printf("**q = %d\n",**q);exit(0);
}

指针运算
& * 关系运算 ++ –

指针与一维数组

#include<stdio.h>
#include<stdlib.h>
int main()
{
//a[i]: a[i] = *(a+i) = *(p+i) = p[i]
//&a[i]: &a[i] = a+i = p+i = &p[i]
//a 和 p 的区别 a是数组名是常量  p是指针变量  a++ 报错 p++ 不报错
//*a = a[0]
//p++  p=p+1; p的指向发生变化
//p+1  p的指向没变
//数组名是对某连续空间的抽象  int a[3] = {1,2,3};int *p = a;int i;//for(i = 0;i <sizeof(a)/sizeof(*a);i++) for(i = 0;i <sizeof(a)/sizeof(a[0]);i++){printf("%p-->%d\n",&a[i],a[i]);	printf("%p-->%d\n",a+i,a[i]);	printf("%p-->%d\n",p+i,a[i]);	printf("%p-->%d\n",p+i,*(p+i));	}printf("\n");	exit(0);
}

#include<stdio.h>
#include<stdlib.h>
int main()
{int a[] = {5,7,8,2,3};int y;int *p = &a[1];;y = (*--p)++;  //(*--p) = (*--p) + 1  先赋值 再自增printf("y = %d\n",y);	//5printf("a[0] = %d\n",a[0]);	//6exit(0);
}

指针与二维数组

int main()
{int a[2][3] = {1,2,3,4,5,6};int i,j;int *p;printf("%p %p\n",a,a+1);// int *p; p = a; waring  行指针a  取* 相当于降级为列指针 *（a+i）+j// p = *(a) 或者 p = &a[0]b[0] a降级为列指针   p 只能在列上移动for(i = 0;i<2;i++){for(j = 0;j<3;j++){printf("%p->%d\n",&a[i][j],a[i][j]);printf("%p->%d\n",*(a+i)+j,*(*(a+i)+j));}printf("\n");}}

数组指针：存储类型数据类型（*指针名【下标】） = 值
如 int (*p)[3]; -> type name; -> int[3] *p;

int main()
{int a[2][3] = {1,2,3,4,5,6};int i,j;int *p = *a;int (*q)[3] = a;//声明了一个数组指针printf("%p %p\n",a,a+1);printf("%p %p\n\n",q,q+1);for(i = 0;i<2;i++){for(j = 0;j<3;j++){printf("%p->%d\n",&a[i][j],a[i][j]);printf("%p->%d\n",*(a+i)+j,*(*(a+i)+j));}printf("\n");}exit(0);
}

指针与字符数组

#include<stdio.h>
#include<stdlib.h>
int main()
{char *str = "hello";printf("%d %d\n",sizeof(str),strlen(str));//8 5//(F)  strcpy(str,"world");  此时动作为 world想要去覆盖str指向的常量 str = "world";//指针改变指向puts(str);//hello
/*char str[] = "hello";printf("%d %d\n",sizeof(str),strlen(str));//6 5区别 #if 0char str[] = "outputs";//F str = "inputs";//数组名是地址常量strcpy(str,"inputs");puts(str);
#endif/*char str[] = "hello world!";char *p = str+7;puts(str);puts(p);*/exit(0);
}