负数被存储为2的内存补，请问CPU知道这是否是正面或负面的？ [英] Negative numbers are stored as 2's complement in memory, how does the CPU know if it's negative or positive?

问题描述

-1可以重新$ P $ 4位二进制psented作为（补）1111

-1 can be represented in 4 bit binary as (2's complement) 1111

15也被重新psented 1111 $ P $。

15 is also represented as 1111.

那么，如何CPU 15 -1和区分时，它从内存中获取价值？

So, how does CPU differentiate between 15 and -1 when it gets values from memory?

推荐答案

该CPU不关心字节是否持有-1或15当它移动从一个地方到另一个地方。有作为签署的移动这样的东西。（为相同尺寸的位置 - 存在用于更大或更小的目的地有符号移动）

The CPU doesn't care whether a byte holds -1 or 15 when it moves it from one place to another. There's no such thing as a "signed move" (to a location of the same size - there is a signed move for larger or smaller destinations).

CPU只在乎当它在字节算术重新presentation。该CPU是否知道做根据了选购code，你（或代表你的编译器）选择符号或无符号运算。

The CPU only cares about the representation when it does arithmetic on the byte. The CPU knows whether to do signed or unsigned arithmetic according to the op-code that you (or the compiler on your behalf) chose.

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