这是因为实际的源代码和变量绑定可以更改，这是建立在环境或者构建宏预处理程序指令的时间定义的基础上的。

This is because the actual source code and the variable binding can change, based on the environment or the build time definitions of macros and preprocessor commands.

youdao

我们假定程序中指令执行所花费的时间是可以忽略的，但实际上它还是会引入一些偏差。

We assume that the time spent executing the instructions in the program is negligible, but there is a slight bias introduced by that time.

youdao

此应用程序的响应时间必须很短：规定为发出指令后 3 秒内。

The application's response time needs to be very short: As stipulated, it is to be on the order of three seconds.

youdao

Remember last time, I said that there's different kinds of complexity in our code, and I suggested for simple branching programs, the amount of time it takes to run that program is, in essence, bounded by the number of instructions, because you only execute each instruction at most once.

但是这里有个很重要的点,记得上节课，我提过在我们的代码中，有不同种类的复杂度，而且我还说了对于简单的分支程序,运行这种程序需要的总体时间,大体上，是和指令的数目相关的,因为每个指令只会被执行最多一次。

麻省理工公开课 - 计算机科学及编程导论课程节选