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。
2
If a function is executing, then the stack pointer is pointing to the top of the whole stack, which is also the top of that function's activation record.