Не работает пример из книги Лафоре

#include <iostream>
#include <string>                //for strcpy(), etc.
using namespace std;
////////////////////////////////////////////////////////////////
class String                      //base class
{
protected:                     //Note: can't be private
    enum { SZ = 20 };           //size of all String objects
    char str[SZ];               //holds a C-string
public:
    String()                    //constructor 0, no args
    {
        str[0] = '\0';
    }
    String(char s[])          //constructor 1, one arg
    {
        strcpy_s(str, s);
    }      //  convert string to String
    void display() const        //display the String
    {
        cout << str;
    }
    operator char*()            //conversion function
    {
        return str;
    }          //convert String to C-string
};
////////////////////////////////////////////////////////////////
class Pstring : public String     //derived class 
{
public:
    Pstring(char s[]);        //constructor
    void display()
    {
        String::display();
    }
};
//--------------------------------------------------------------
Pstring::Pstring(char s[])      //constructor for Pstring
{
    if (strlen(s) > SZ - 1)           //if too long,
    {
        for (int j = 0; j < SZ - 1; j++)   //copy the first SZ-1
        {
            str[j] = s[j];           //characters "by hand"
            str[j] = '\0';
        }              //add the null character
    }
    else                           //not too long,
        String(s);                  //so construct normally
    
}
////////////////////////////////////////////////////////////////
int main()
{                                        //define String
    Pstring s1 = "This is a very long string which is probably "
        "no, certainly--going to exceed the limit set by SZ.";
    cout << "\ns1="; s1.display();           //display String
 
    Pstring s2 = "This is a short string.";  //define String
    cout << "\ns2="; s2.display();           //display String
    cout << endl;
    system("pause");
    return 0;
}

for (int j = 0; j < SZ - 1; j++)   //copy the first SZ-1
        {
            str[j] = s[j];           //characters "by hand"
            str[j] = '\0';
        }

int j;
for (j = 0; j < SZ - 1; j++)
    str[j] = s[j];
 
str[j] = '\0';

str[SZ - 1]='\0';