Purify keeps track of the status of every byte of memory used by your program and uses four colors to represent the status: red, yellow, green, and blue.
The stack is coordinated with a stack pointer that keeps track of storage and retrieval of each byte or word of information in the stack.
栈和一个栈指针配合工作，栈指针随时指示要存取的每个字或字节信息在栈中的位置。
3
The reason for excluding 65535 is pragmatic: likely implementations will use a 2-byte integer to track both a local's index, as well as the total number of locals for a given method.