什么是C Runtime library?

[THINK511]

什么是C Runtime library?它和windows 的API函数有什么区别和联系呢？我们在做程序的时候是使用C Runtime library好呢还是windows API好呢？

[bossmao]

C Run-Time Libraries
The following table lists the release versions of the C run-time library files, along with their associated compiler options and environment variables. Prior to Visual C++ 4.2, the C run-time libraries contained the iostream library functions. In Visual C++ 4.2 and later, the old iostream library functions have been removed from LIBC.LIB, LIBCMT.LIB, and MSVCRT.LIB. (This change was made because the Standard C++ library has been added to Visual C++, and it contains a new set of iostream libraries. Thus, two sets of iostream functions are now included in Visual C++.) The old iostream functions now exist in their own libraries: LIBCI.LIB, LIBCIMT.LIB, and MSVCIRT.LIB. The new iostream functions, as well as many other new functions, exist in the Standard C++ libraries: LIBCP.LIB, LIBCPMT.LIB, and MSVCPRT.LIB.

The Standard C++ library and the old iostream library are incompatible, and only one of them can be linked with your project. See Port to the Standard C++ Library and theStandard C++ Library Overview for details.

When you build a release version of your project, one of the basic C run-time libraries (LIBC.LIB, LIBCMT.LIB, and MSVCRT.LIB) is linked by default, depending on the compiler option you choose (single-threaded, multithreaded, or DLL). Depending on the headers you use in your code, a library from the Standard C++ libraries or one from the old iostream libraries may also be linked:

[rivershan]

see MSDN~

and

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Windows应用程序调用的函数可分为C/C++运行时库函数以及Windows API函数两大部份。

Windows API大家都很熟悉了，那什么是C/C++运行时库呢？所谓C/C++运行时库（C/C++Run-time Library），就是由系统提供的一些库文件（可以是静态链接库，也可以是动态链接库），里面含有Windows应用程序所用的最基本和最常用的C/C++运行时库函数、应用程序初始化代码、错误处理代码（例如0做除数的处理）等。你写的程序可以没有MATHS.LIB，程序照样运行，只是不能处理复杂的数学运算，不过如果没有了C运行时库，main()就不会被调用，exit()也不能被响应。

在编写Windows应用程序的时候，默认情况下，系统会自动链接到这些C/C++运行时库之中去，调用一些C/C++运行时库中的函数对程序进行一些初始化工作，然后再来调用我们的应用程序中的Windows API函数。

[Caps77]

C Runtime library 是从c语言延续下来的一些函数，如strcpy,strlen等，适用于任何支持ANSI c的操作系统
而win api程序与windows操作系统交互的接口

[THINK511]

那我们在做程序的时候是使用C Runtime library好呢还是windows API好呢？我现在在看《windows系统编程》，书中说最好使用windowsAPI函数，因为好多已经运行的程序如explore等都已经使用了windowsAPI函数，所以在内存中已经存在了。这让我很困惑，难道说C Runtime Library在这个时候在内存中就不存在了吗？那还叫什么Runtime？