SICP(Structure and Interpretation of Computer Programs)

1.Welcome to the real world.

From now on , we jumped out of the Matrix world of Lisp, and go down to the deeper layer, that is physical-level.

2.We can use another different design in physical world , but the abstraction world is still no-change.

3.Because the abstraction is more close to Truth than the real physical world.

4.The abstraction (software) is the essential purpose, and physical(hardware) is just one kind of implementation.

5.The Abstraction world is so elegance, but the implementation looks so heavy.