第34课 多维数组和多维指针

1. 指向指针的指针

（1）指针的本质是变量，会占用一定的内存空间

（2）可以定义指针的指针来保存指针变量的地址值

（3）指针是个变量，同样也存在传值调用与传址调用

【实例分析】遍历二维数组

2. 数组名

（1）一维数组名代表数组首元素的地址：int a[5];a的类型为int*

（2）二维数组名同样代表数组首元素的地址：如int a[3][5]，a的类型为int(*)[5]。

【实例分析】数组的信息

#include <stdio.h>

int main(int argc,char* argv[], char* env[])
{

    int a[3][5] = {0};
    int c;

    printf("Information for array：a[3][5]：\n");
    printf("a = 0x%08X, a + 1 = 0x%08X, sizeof(a) = %d\n", a, a + 1, sizeof(a));
    printf("&a = 0x%08X, &a + 1 = 0x%08X, sizeof(&a) = %d, sizeof(*&a) = %d\n",
               &a, &a + 1, sizeof(&a),sizeof(*&a));

    printf("\n");
    //a[i]指向一个一维数组的首元素，a[i]+1指向该行第2个元素。sizeof(a[i])时不能看成首元素，而是这行整个一维数组
    for(c=0;c< 5;c++)
    {
      printf("a[%d] = 0x%08X, a[%d] + 1 = 0x%08X, sizeof(a[%d]) = %d,\n",
                c, a[c], c, a[c] + 1,c, sizeof(a[c]));
    }

    printf("\n");
    //对a[i]进行&取地址符时，a[i]不能看作这一行的首元素，而是整个一维数组。即&a[i]表示第i+1的整个数组    //&a[i]+1表示下一行。

for(c=0;c< 5;c++)
    {
      printf("&a[%d] = 0x%08X, &a[%d] + 1 = 0x%08X, sizeof(&a[%d]) = %d, sizeof(*&a[%d]) = %d\n",
               c, &a[c],c, &a[c] + 1,c, sizeof(&a[c]), c, sizeof(*&a[c]));
    }

    return 0;
}

/*
输出结果：
Information for array：a[3][5]：
a = 0x0023FE80, a + 1 = 0x0023FE94, sizeof(a) = 60
&a = 0x0023FE80, &a + 1 = 0x0023FEBC, sizeof(&a) = 4, sizeof(*&a) = 60

a[0] = 0x0023FE80, a[0] + 1 = 0x0023FE84, sizeof(a[0]) = 20,
a[1] = 0x0023FE94, a[1] + 1 = 0x0023FE98, sizeof(a[1]) = 20,
a[2] = 0x0023FEA8, a[2] + 1 = 0x0023FEAC, sizeof(a[2]) = 20,
a[3] = 0x0023FEBC, a[3] + 1 = 0x0023FEC0, sizeof(a[3]) = 20,
a[4] = 0x0023FED0, a[4] + 1 = 0x0023FED4, sizeof(a[4]) = 20,

&a[0] = 0x0023FE80, &a[0] + 1 = 0x0023FE94, sizeof(&a[0]) = 4, sizeof(*&a[0]) = 20
&a[1] = 0x0023FE94, &a[1] + 1 = 0x0023FEA8, sizeof(&a[1]) = 4, sizeof(*&a[1]) = 20
&a[2] = 0x0023FEA8, &a[2] + 1 = 0x0023FEBC, sizeof(&a[2]) = 4, sizeof(*&a[2]) = 20
&a[3] = 0x0023FEBC, &a[3] + 1 = 0x0023FED0, sizeof(&a[3]) = 4, sizeof(*&a[3]) = 20
&a[4] = 0x0023FED0, &a[4] + 1 = 0x0023FEE4, sizeof(&a[4]) = 4, sizeof(*&a[4]) = 20
*/