# 指针

## 指针递增

```c
#include <stdio.h>

const int MAX = 3;

int main ()
{
   int  var[] = {10, 100, 200};
   int  i, *ptr;

   /* 指针中的数组地址 */
   ptr = var;
   for ( i = 0; i < MAX; i++)
   {

      printf("存储地址：var[%d] = %x\n", i, ptr );
      printf("存储值：var[%d] = %d\n", i, *ptr );

      /* 移动到下一个位置 */
      ptr++;
   }
   return 0;
}

/**
存储地址：var[0] = bf882b30
存储值：var[0] = 10
存储地址：of var[1] = bf882b34
存储值： var[1] = 100
存储地址：of var[2] = bf882b38
存储值：var[2] = 200
*/
```

## 指针递减

```c
#include <stdio.h>

const int MAX = 3;

int main ()
{
   int  var[] = {10, 100, 200};
   int  i, *ptr;

   /* 指针中最后一个元素的地址 */
   ptr = &var[MAX-1];
   for ( i = MAX; i > 0; i--)
   {

      printf("存储地址：var[%d] = %x\n", i-1, ptr );
      printf("存储值：var[%d] = %d\n", i-1, *ptr );

      /* 移动到下一个位置 */
      ptr--;
   }
   return 0;
}

/*
存储地址：var[2] = 518a0ae4
存储值：var[2] = 200
存储地址：var[1] = 518a0ae0
存储值：var[1] = 100
存储地址：var[0] = 518a0adc
存储值：var[0] = 10
**/
```

## 指针数组

```c
#include <stdio.h>

const int MAX = 3;

int main ()
{
   int  var[] = {10, 100, 200};
   int i, *ptr[MAX];

   for ( i = 0; i < MAX; i++)
   {
      ptr[i] = &var[i]; /*赋值为整 数的地址 */
   }
   for ( i = 0; i < MAX; i++)
   {
      printf("Value of var[%d] = %d\n", i, *ptr[i] );
   }
   return 0;
}
```

```c
#include <stdio.h>

const int MAX = 4;

int main ()
{
   const char *names[] = {
                   "Zara Ali",
                   "Hina Ali",
                   "Nuha Ali",
                   "Sara Ali",
   };
   int i = 0;

   for ( i = 0; i < MAX; i++)
   {
      printf("Value of names[%d] = %s\n", i, names[i] );
   }
   return 0;
}
```

## 指向指针的指针

```c
int  var;
int  *ptr;
int  **pptr;
var = 3000;

/* 获取 var 的地址 */
ptr = &var;

/* 使用运算符 & 获取 ptr 的地址 */
pptr = &ptr;

/* 使用 pptr 获取值 */
printf("Value of var = %d\n", var );
printf("Value available at *ptr = %d\n", *ptr );
printf("Value available at **pptr = %d\n", **pptr);
```

## 函数返回指针

```c
#include <stdio.h>
#include <time.h>
#include <stdlib.h> 

/* 要生成和返回随机数的函数 */
int * getRandom( )
{
   static int  r[10];
   int i;

   /* 设置种子 */
   srand( (unsigned)time( NULL ) );
   for ( i = 0; i < 10; ++i)
   {
      r[i] = rand();
      printf("%d\n", r[i] );
   }

   return r;
}

/* 要调用上面定义函数的主函数 */
int main ()
{
   /* 一个指向整数的指针 */
   int *p;
   int i;

   p = getRandom();
   for ( i = 0; i < 10; i++ )
   {
       printf("*(p + [%d]) : %d\n", i, *(p + i) );
   }

   return 0;
}
```


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