数组与指针

背景：

　　这片文章主要是记录以前的误区，以前C/C++这块还是大学中学习的一点知识，好久不用，基本都忘记啦。一直误以为数组的大小和指针的大小一样，最近通过学习learn c the hard way发现并不是这样。这个其实没有太多可说的，直接上demo。

demo代码:

#include <stdio.h>

int main(int argc, char *argv[])
{
    int areas[] = {10, 12, 13, 14, 20};
    char name[] = "Zhaosc";
    char full_name[] = {
        'Z', 'h', 'a', 'o',
        ' ', 'S', 'h', 'u', ' ',
        'c', 'h', 'a', 'o', '\0'
    };
    
    int a = 10;
    int *a_ptr = &a;
    char c = 'b';
    char *c_ptr = &c;

    printf("the size of the variable int pointer is %ld.\n", sizeof(a_ptr));
    printf("the size of the variable char pointer is %ld.\n", sizeof(c_ptr));

    // WARNING: On some systems you may have to change the
    // %ld in this code to a %u since it will use unsigned ints
    printf("The size of an int: %ld\n", sizeof(int));
    printf("The size of areas (int[]): %ld\n",
           sizeof(areas));
    printf("The number of ints in areas: %ld\n",
           sizeof(areas) / sizeof(int));
    printf("The first area is %d, the 2nd %d.\n",
           areas[0], areas[1]);
    
    printf("The size of a char: %ld\n", sizeof(char));
    printf("The size of name (char[]): %ld\n",
           sizeof(name));
    printf("The number of chars: %ld\n",
           sizeof(name) / sizeof(char));
    
    printf("The size of full_name (char[]): %ld\n",
           sizeof(full_name));
    printf("The number of chars: %ld\n",
           sizeof(full_name) / sizeof(char));
    
    printf("name=\"%s\" and full_name=\"%s\"\n",
           name, full_name);
    
    return 0;
}

运行结果：

zhaoscmatoMacBook-Pro:c zhaosc$ ./ex8
the size of the variable int pointer is 8.
the size of the variable char pointer is 8.
The size of an int: 4
The size of areas (int[]): 20
The number of ints in areas: 5
The first area is 10, the 2nd 12.
The size of a char: 1
The size of name (char[]): 7
The number of chars: 7
The size of full_name (char[]): 14
The number of chars: 14
name="Zhaosc" and full_name="Zhao Shu chao"

分析：

根据输出一行一行分析

1.int和char的指针在内存的大小都是8个字节，指针在内存中的大小和指针类型没有区别，例如函数指针也是一样的。

2.int在内存占用4个字节，这个是不确定的，和具体的操作系统位数有关系。

3.int数组在内存中占用20个字节，正好是4*5.areas中有5个整数。

4.char在内存中占用1个字节，这个是确定的。

5.char数组占用内存是7个字节，同样为1*7.

Note：如博文中存在问题，请大家及时指出，我会及时纠正，谢谢。