Advice: Use the C++ Versions of C Library Headers

Advice: Use the C++ Versions of C Library Headers

建议：采用 C 标准库头文件的 C++ 版本

In addition to facilities defined specifically for C++, the C++ library incorporates the C library. The cctype header makes available the C library functions defined in the C header file named ctype.h.

C++ 标准库除了定义了一些选定于 C++ 的设施外，还包括 C 标准库。C++ 中的头文件 cctype 其实就是利用了 C 标准库函数，这些库函数就定义在 C 标准库的 ctype.h 头文件中。

The standard C headers names use the form name.h. The C++ versions of these headers are named cnamethe C++ versions remove the .h suffix and precede the name by the letter c. Thec indicates that the header originally comes from the C library. Hence, cctype has the same contents as ctype.h, but in a form that is appropriate for C++ programs. In particular, the names defined in the cname headers are defined inside the std namespace, whereas those defined in the .h versions are not.

C 标准库头文件命名形式为 name 而 C++ 版本则命名为 cname ，少了后缀，.h 而在头文件名前加了 c 表示这个头文件源自 C 标准库。因此，cctype 与 ctype.h 文件的内容是一样的，只是采用了更适合 C++程序的形式。特别地，cname 头文件中定义的名字都定义在命名空间 std 内，而 .h 版本中的名字却不是这样。

Ordinarily, C++ programs should use the cname versions of headers and not the name.h versions. That way names from the standard library are consistently found in the std namespace. Using the .h headers puts the burden on the programmer to remember which library names are inherited from C and which are unique to C++.

通常，C++ 程序中应采用 cname 这种头文件的版本，而不采用 name.h 版本，这样，标准库中的名字在命名空间 std 中保持一致。使用 .h 版本会给程序员带来负担，因为他们必须记得哪些标准库名字是从 C 继承来的，而哪些是 C++ 所特有的。

例如：

目录/usr/include/c++/4.3内包含若干C标准库的替代，如cstring（对应于string.h)

/** @file cstring
 *  This is a Standard C++ Library file.  You should @c #include this file
 *  in your programs, rather than any of the "*.h" implementation files.
 *
 *  This is the C++ version of the Standard C Library header @c string.h,
 *  and its contents are (mostly) the same as that header, but are all
 *  contained in the namespace @c std (except for names which are defined
 *  as macros in C).
 */