指针的八种用法

// ptr_ops.c   --指针操作
#include <stdio.h>
int main(void)    {
     int urn[5] = { 100,200,300,400,500 };
     int *ptr1, *ptr2, *ptr3;
     ptr1= urn;   //把一个地址赋给指针
     ptr2 = &urn[2];    //把一个地址赋给指针
    
     //解引用指针，以及获得指针的地址
     printf("pointer value, dereferenced pointer, pointer address:\n");
     printf("ptr1 = %p, *ptr1 = %d, &ptr1 = %p\n",ptr1,*ptr1,&ptr1);
    
     //指针加法
     ptr3 = ptr1 + 4;
     printf("\nadding an int to a pointer:\n");
     printf("ptr1 + 4 = %p, *(ptr1+4) = %d\n",ptr1+4,*(ptr1+4));
    
     ptr1++;  //递增指针
     printf("\nvalues after ptr1++:\n");
     printf("ptr1 = %p, *ptr1 = %d, &ptr1 = %p\n", ptr1, *ptr1, &ptr1);
    
     ptr2--;  //递减指针
     printf("\nvalues after -- ptr2:\n");
     printf("ptr2 = %p, *ptr2 = %d, &ptr2 = %p\n",ptr2, *ptr2, &ptr2);
    
     --ptr1;   //恢复为初始值
     ++ptr2;   //恢复为初始值
    
     printf("\nPointers reset to original values:\n");
     printf("ptr1 = %p, ptr2 = %p\n", ptr1,ptr2);
    
     //一个指针减去另一个指针
     printf("\nsubtracting one pointer from another:\n");
     printf("ptr2 = %p,ptr1 = %p,ptr2 - ptr1 = %d\n",ptr2,ptr1,ptr2-ptr1);
    
     //一个指针减去一个整数
     printf("\nsubtracting an int from a pointer:\n");
     printf("ptr3 = %p,ptr3 - 2 = %p\n",ptr3,ptr3 - 2);
    
     return 0;
}