C语言面向对象程序设计5.ppt

* 6. I/O流与文件 (I/O Stream and File) 流--指字节序列，用于内存与外设缓冲区之间交换数据 I----Input（输入）； O----Output（输出） 6.1 标准I/O流类和对象 标准I/O流：输入输出设备为键盘和显示器（打印机）：cout，cin，cerr，clog 串流: 读写字符数组流（即把字符串看成为设备） 文件I/O流：永久存储介质设备上的数据组织为文件，如硬盘、软盘、光盘等 显示器 键盘 内存 输出O 输入I 外存 内存 写入O 读出I 内存 内存 字符数组 写入O 读出I 标准I/O流 串流 文件I/O流 istrstream类 ios类 istream类 ostream类 iostream类 ifstream类 ofstream类 fstream类 virtual public virtual public 多重继承 ostrstream类 strstream类 include文件: ios.h istream.h ostream.h iostream.h fstream.h strstrea.h 系统定义四个全局对象: cin, cout, cerr, clog, 用于处理标准I/O流 istream.h文件中定义 extern istream_withassign _CRTIMP cin; ostream.h文件中定义 extern ostream_withassign _CRTIMP cout; extern ostream_withassign _CRTIMP cerr; extern ostream_withassign _CRTIMP clog; ios基类以及派生类定义了系统提供的关于流处理的接口 ostream.h文件中的部分内容: class _CRTIMP ostream : virtual public ios { //为了多重继承的正确,用virtual public: ostream(streambuf*); virtual ~ostream(); //虚函数, 可以多态地撤销对象 ostream flush(); int opfx(); void osfx(); inline ostream operator (ostream (__cdecl * _f)(ostream)); //重载运算符, inline ostream operator (ios (__cdecl * _f)(ios)); //可处理各种数据类型 ostream operator (const char *); inline ostream operator (const unsigned char *); inline ostream operator (const signed char *); inline ostream operator (char); ostream operator (unsigned char); inline ostream operator (signed char); ostream operator (short); ostream operator (unsigned short); ostream operator (int); ostream operator (unsigned int); ostream operator (long); ostream operator (unsigned long); inline ostream operator (float); ostream operator (double); ostream operator (long double); ostream operator (const void *); ostream operator (streambuf*); inline ostream put(char); ostream put(unsigned char); inline ostream put(signed char); ostream write(const