又困惑了，指针问题

int main(int argc, char* argv[])
{
        try
        {
        const char *str = "iosd/dfdfdsfdsfdsf223";
        char *buf1 = "";
        sscanf(str,"%*[^/]/%s",buf1);
        cout<<buf1<<endl;

        char *str1="";
        cout<<str1<<endl;

        cin.get();
        return 0;
        }
        catch(...)
        {
          return 1;
        }
}
做个小实验发现如下问题：
怎么刚定义完char *str1="";就有值了呢，在哪给赋的呢，高手费心看看吧