我先回答你们的具体问题。

1.什么是源级别?它是否与源代码有关?

Yes, the term source level refers to the level of source code. The term level refers to the semantic level of the computation requirements as they get translated from the application domain level to the source code level and from the source code level to the machine code level (binary codes). The application domain level refers what end-users of the software want and specify as their computation requirements. The source code level refers to what programmers make of the application level requirements and then specify as a program in a certain language.

程序如何在源级进行通信?或者库的源代码包含在主程序中?

语言API专门指一种语言需要(指定)(即接口)用该语言编写可重用模块的所有东西。可重用程序符合这些接口(API)要求，以便在相同语言的其他程序中重用。每次重用都需要符合相同的API需求。所以，“沟通”这个词指的是重用。

Yes, source code (of a reusable module; in the case of C/C++, .h files ) getting included (copied at pre-processing stage) is the common way of reusing in C/C++ and is thus part of C++ API. Even when you just write a simple function foo() in the global space of a C++ program and then call the function as foo(); any number of times is reuse as per the C++language API. Java classes in Java packages are reusable modules in Java. The Java beans specification is also a Java API enabling reusable programs (beans) to be reused by other modules ( could be another bean) with the help of runtimes/containers (conforming to that specification).

关于语言API和ABI之间的区别，以及面向服务的API与语言API的区别，我在SO方面的回答应该会有所帮助。

这是我的外行解释:

API——考虑包含文件。它们提供编程接口。 ABI——想想内核模块。当你在某个内核上运行它时，它必须同意如何在没有包含文件的情况下进行通信，即作为低级二进制接口。

API是人类使用的。我们编写源代码。当我们编写程序并想要使用一些库函数时，我们编写如下代码:

long howManyDecibels = 123L;
int ok = livenMyHills(howManyDecibels);

and we needed to know that there is a method livenMyHills(), which takes a long integer parameter. So as a Programming Interface it's all expressed in source code. The compiler turns this into executable instructions which conform to the implementation of this language on this particular operating system. And in this case result in some low level operations on an Audio unit. So particular bits and bytes are squirted at some hardware. So at runtime there's lots of Binary level action going on which we don't usually see.

在二进制级别，必须对在二进制级别传递的字节有一个精确的定义，例如4字节整数中的字节顺序，或者复杂数据结构的布局——是否有填充字节来对齐一些值。这个定义就是ABI。

API:应用程序接口

这是您从应用程序/库中公开的公共类型/变量/函数集。

在C/ c++中，这是在应用程序附带的头文件中公开的内容。

ABI:应用程序二进制接口

这就是编译器构建应用程序的方式。 它定义了一些东西(但不限于):

参数如何传递给函数(寄存器/堆栈)。 谁从堆栈中清除参数(调用方/被调用方)。 返回值的位置。 异常如何传播。

我先回答你们的具体问题。

1.什么是源级别?它是否与源代码有关?

Yes, the term source level refers to the level of source code. The term level refers to the semantic level of the computation requirements as they get translated from the application domain level to the source code level and from the source code level to the machine code level (binary codes). The application domain level refers what end-users of the software want and specify as their computation requirements. The source code level refers to what programmers make of the application level requirements and then specify as a program in a certain language.

程序如何在源级进行通信?或者库的源代码包含在主程序中?

语言API专门指一种语言需要(指定)(即接口)用该语言编写可重用模块的所有东西。可重用程序符合这些接口(API)要求，以便在相同语言的其他程序中重用。每次重用都需要符合相同的API需求。所以，“沟通”这个词指的是重用。

Yes, source code (of a reusable module; in the case of C/C++, .h files ) getting included (copied at pre-processing stage) is the common way of reusing in C/C++ and is thus part of C++ API. Even when you just write a simple function foo() in the global space of a C++ program and then call the function as foo(); any number of times is reuse as per the C++language API. Java classes in Java packages are reusable modules in Java. The Java beans specification is also a Java API enabling reusable programs (beans) to be reused by other modules ( could be another bean) with the help of runtimes/containers (conforming to that specification).

关于语言API和ABI之间的区别，以及面向服务的API与语言API的区别，我在SO方面的回答应该会有所帮助。

API -应用程序编程接口是一个编译时接口，开发人员可以使用它来使用源代码中的库、操作系统、核心调用等非项目功能

ABI[关于]-应用程序二进制接口是一个运行时接口，由程序在执行期间用于机器代码中的组件之间的通信