Imagine that you are a boss and you have an assistant and a maid, and you give them a list of tasks to do, the assistant (compile time) will grab this list and make a checkup to see if the tasks are understandable and that you didn't write in any awkward language or syntax, so he understands that you want to assign someone for a Job so he assign him for you and he understand that you want some coffee, so his role is over and the maid (run time)starts to run those tasks so she goes to make you some coffee but in sudden she doesn’t find any coffee to make so she stops making it or she acts differently and make you some tea (when the program acts differently because he found an error).

将源代码转换为“屏幕|磁盘|网络”可以(大致)以两种方式发生;称之为编译和解释。

在编译程序中(例如c和fortran):

源代码被输入到另一个程序(通常称为编译器)，该程序生成一个可执行程序(或一个错误)。 运行可执行文件(通过双击它，或在命令行上键入它的名称)

在第一步发生的事情被称为在“编译时”发生，在第二步发生的事情被称为在“运行时”发生。

在解释程序中(例如MicroSoft basic(在dos上)和python(我想)):

源代码被输入到另一个程序(通常称为解释器)，该程序直接“运行”它。在这里，解释器充当程序和操作系统(或非常简单的计算机中的硬件)之间的中间层。

在这种情况下，编译时和运行时之间的差异很难确定，而且与程序员或用户的关系也小得多。

Java是一种混合，代码被编译成字节码，然后在虚拟机上运行，虚拟机通常是字节码的解释器。

还有一种中间情况，即程序被编译为字节码并立即运行(如在awk或perl中)。

您可以通过阅读实际代码来理解代码编译结构。运行时结构并不清楚，除非您了解所使用的模式。

编译时和运行时之间的差异就是精明的理论家所说的阶段差异的一个例子。它是最难学习的概念之一，特别是对于没有太多编程语言背景的人来说。要解决这个问题，我发现问一下很有帮助

程序满足哪些不变量? 在这个阶段会出现什么问题? 如果阶段成功，后置条件是什么(我们知道什么)? 输入和输出是什么(如果有的话)?

编译时

The program need not satisfy any invariants. In fact, it needn't be a well-formed program at all. You could feed this HTML to the compiler and watch it barf... What can go wrong at compile time: Syntax errors Typechecking errors (Rarely) compiler crashes If the compiler succeeds, what do we know? The program was well formed---a meaningful program in whatever language. It's possible to start running the program. (The program might fail immediately, but at least we can try.) What are the inputs and outputs? Input was the program being compiled, plus any header files, interfaces, libraries, or other voodoo that it needed to import in order to get compiled. Output is hopefully assembly code or relocatable object code or even an executable program. Or if something goes wrong, output is a bunch of error messages.

运行时

We know nothing about the program's invariants---they are whatever the programmer put in. Run-time invariants are rarely enforced by the compiler alone; it needs help from the programmer. What can go wrong are run-time errors: Division by zero Dereferencing a null pointer Running out of memory Also there can be errors that are detected by the program itself: Trying to open a file that isn't there Trying find a web page and discovering that an alleged URL is not well formed If run-time succeeds, the program finishes (or keeps going) without crashing. Inputs and outputs are entirely up to the programmer. Files, windows on the screen, network packets, jobs sent to the printer, you name it. If the program launches missiles, that's an output, and it happens only at run time :-)

这里有一个非常简单的答案:

Runtime and compile time are programming terms that refer to different stages of software program development. In order to create a program, a developer first writes source code, which defines how the program will function. Small programs may only contain a few hundred lines of source code, while large programs may contain hundreds of thousands of lines of source code. The source code must be compiled into machine code in order to become and executable program. This compilation process is referred to as compile time.(think of a compiler as a translator)

用户可以打开并运行编译后的程序。当应用程序正在运行时，它被称为运行时。

术语“运行时”和“编译时”经常被程序员用来指代不同类型的错误。编译时错误是一种问题，例如语法错误或缺少文件引用，从而阻止程序成功编译。编译器产生编译时错误，并通常指出源代码的哪一行导致了问题。

如果一个程序的源代码已经被编译成一个可执行程序，那么它在程序运行时可能仍然有错误。例子包括不能工作的特性、意外的程序行为或程序崩溃。这些类型的问题被称为运行时错误，因为它们发生在运行时。

参考

基本上，如果你的编译器能在“编译时”找出你的意思或一个值是什么，它就能硬编码到运行时代码中。显然，如果你的运行时代码每次都要进行计算，那么它会运行得更慢，所以如果你能在编译时确定一些东西，那就更好了。

Eg.

常数合并:

如果我这样写:

int i = 2;
i += MY_CONSTANT;

编译器可以在编译时执行这个计算，因为它知道2是什么，MY_CONSTANT是什么。因此，每次执行时，它都不必执行计算。