/* programNo4.20 */
/***********************************
2017年9月29日17:11:09
Athor：xiyuan255
Course：C++
Contain：ptrstr.cpp
Reference: C++ Primer plus
知识点：
1.在cout和多数C++表达式中，char数组名、char指针以及用引号括起的字符串
常量都被解释为字符串第一个字符的地址。
为什么要这样呢？因为char是字符类型，只要知道字符串的首地址，然后依次
打印出接下来的字符，直到遇到空字符('\0')结束；这样可以缩减工作量。
2.所以在打印数组名时，其实就是打印该数组中的字符串；用双引号括起来的字符
串，其实也是把首字母的地址发给cout，然后依次打印出该字符串。
*************************************/
// ptrstr.cpp -- using pointer to strings
#include <iostream>
#include <cstring> // declare strlen(), strcpy()
int main(void)
{
using namespace std;
char animal[20] = "bear"; // animal holds bear
const char * bird = "wren"; // bird holds address
char * ps; // uninitialized
cout << animal << " and "; // display bear
cout << bird << "\n"; // display wren
// cout << ps << "\n"; // may display garbage, may cause a crash
cout << "Enter a kind of animal: ";
cin >> animal; // ok if input < 20 chars
// cin >> ps; Too horrible a blunder to try; ps doesn't
// point to allocated space
ps = animal; // set ps to point to string
cout << ps << "!\n"; // ok, same sa using animal
cout << "Before using strcpy(): \n";
cout << animal << " at " << (int *) animal << endl;
cout << ps << " at " << (int *) ps << endl;
ps = new char[strlen(animal) + 1]; // get new storage
strcpy(ps, animal); // copy string to new storage
cout << "After using strcpy(): \n";
cout << animal << " at " << (int *) animal << endl;
cout << ps << " at " << (int *) ps << endl;
delete [] ps;
return 0;
}
/**
输出结果：
bear and wren
Enter a kind of animal: fox
fox!
Before using strcpy():
fox at 0016FB84
fox at 0016FB84
After using strcpy():
fox at 0016FB84
fox at 00511990
*/
