无法确定为什么指针变量不会在该程序中寻址字符串中的元素？

Question

我正在尝试使用指针变量来访问字符串的元素，但我的代码出现了问题，生成了编译错误:

#include <stdio.h>
#define MAX 29

char arrayI[250];
char *ptr;

int main(void)
{
ptr = arrayI;

puts("Enter string to arrayI: up to 29 chars:\n");
fgets(arrayI, MAX, stdin);

printf("\n Now printing array by pointer:\n");
printf("%s", *ptr);


ptr = arrayI[1];     //(I set the pointer to the second array char element)
printf("%c", *ptr);  //Here is where I was wanting to use my pointer to 
                     //point to individual array elements.
return 0;
}

我的编译器提示:

[警告] 赋值从整数生成指针而不进行强制转换 [默认启用]

我没有看到我的指针在哪里分配给整数数据类型？有人可以解释为什么我尝试实现指针变量失败了吗？谢谢大家!

Answer 1

#include <stdio.h>
#define MAX 29
// An array declaration that can hold upto 250 characters 
char arrayI[250];
// A pointer variable that can hold the address of a character
char *ptr;
int main(void)
{
   // Assigning the array's base address to the pointer variable
   ptr = arrayI;
   puts("Enter string to arrayI: up to 29 chars:\n");
   fgets(arrayI, MAX, stdin);

   printf("\n Now printing array by pointer:\n");
   // Printing the entire array
   printf("%s", ptr);

   // Now modifying the pointer variable to point to the second character
   ptr = &arrayI[1];     
   // Printing the second character from left in the array
   printf("%c", *ptr);  
}

假设内存分配如下:

假设基地址从4000开始。

      +----------+
4000  |          |    arrayI[0]  
      +----------+
4001  |          |    arrayI[1]
      +----------+
4002  |          |    arrayI[2]
      +----------+
           .
           .
           .
      +----------+
4249  |          |    arrayI[249]
      +----------+

Now ptr = arrayI => 4000

printf("%s",ptr);  //Print the entire string starting from address 4000

Now ptr = &arrayI[1] => 4001

printf("%c", *ptr); // Print valueAt(ptr) => valueAt(4001) => second character of arrayI