Instructions: Language of the

分层解耦，但是仍然需要交流 —— 交流就需要语言：

To command a computer’s hardware, you must speak its language. The words of a computer’s language are called instructions, and its vocabulary is called an instruction set.

但是与人类的语言不同的是：

You might think that the languages of computers would be as diverse as those of people, but in reality, computer languages are quite similar, more like regional dialects than independent languages. Hence, once you learn one, it is easy to pick up others.

背后的原因在于：

This similarity of instruction sets occurs because all computers are constructed from hardware technologies based on similar underlying principles and because there are a few basic operations that all computers must provide.

更重要的是，大家都致力于实现：

to find a language that makes it easy to build the hardware and the compiler while maximizing performance and minimizing cost and energy.

最后引入一个概念：

stored-program concept The idea that instructions and data of many types can be stored in memory as numbers and thus be easy to change, leading to the stored-program computer.

计算机的世界，是数字的。