C语言之指针

指针

1、指针所占内存大小

数据的地址和数据本身没有任何关系,由于指针是间接寻址，所以猜测所有类型的指针大小相同
指针大小是由当前CPU运行模式的寻址位数决定,是固定的。

证实如下：
pointer.c

#include<stdio.h>
#include<stdbool.h>//在C99标准里面，定义了bool类型变量。引入头文件 <stdbool.h>，就能在C语言里面正常使用bool类型
int main(){
   
    char* char_ptr=NULL;
    int* int_ptr=NULL;
    float* float_ptr=NULL;
    double* double_ptr=NULL;
    void* void_ptr=NULL;
    bool* bool_ptr=NULL;

    printf("The size of char_ptr is %d\n",sizeof(char_ptr));
    printf("The size of int_ptr is %d\n",sizeof(int_ptr));
    printf("The size of float_ptr is %d\n",sizeof(float_ptr));
    printf("The size of double_ptr is %d\n",sizeof(double_ptr));
    printf("The size of void_ptr is %d\n",sizeof(void_ptr));
    printf("The size of bool_ptr is %d\n",sizeof(bool_ptr));
}

运行结果：

The size of char_ptr is 4
The size of int_ptr is 4
The size of float_ptr is 4
The size of double_ptr is 4
The size of void_ptr is 4
The size of bool_ptr is 4

2、* 和 &

*:间接访问
&:取地址

例子：

#include<stdio.h>
int main(){
   
  int *a=NULL;
  int b=10;
  printf("The address of a is %d\n",&a);
  printf("The address of b is %d\n",&b);
  a=&b;
  printf("The value of a is %d\n",a);
  *a