this makes it easy for functions to know where their activation record is -- they are simply defined in terms of the stack pointer.
这对函数了解自己的活动记录在什么地方提供了方便 ——它们可以使用堆栈指针的形式简单地进行定义。
this is because each time a function is called, it has an activation record (also called a stack frame) associated with it.
这是由于每次调用一个函数时,都有一个相关活动记录(activation record) (也称为堆栈帧)。
only when the function call is completely finished is the space for the activation record released for reuse (more on this later).
直到函数调用彻底完成时,活动记录使用的空间才会被释放以便重用(更多信息请参看后面的介绍)。
the activation record isn't needed anymore, so we are going to cut it out and redirect the tail-called function back to the function that called us.
再也不需要活动记录(activation record),所以我们将删掉它,并将尾部调用的函数重定向返回到调用我们的函数。