> For the complete documentation index, see [llms.txt](https://docs.1l.lol/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.1l.lol/basics/units.md).

# 单位

### 数据存储单位

* **最小单位：比特（bit）**，取值 0 或 1
* **基本单位：字节（Byte）**，`1 Byte = 8 bit`
* 一个英文字符占 1 字节，一个汉字（UTF-8）通常占 3 字节

### 单位换算

| 单位   | 换算      |
| ---- | ------- |
| 1 B  | 8 bit   |
| 1 KB | 1024 B  |
| 1 MB | 1024 KB |
| 1 GB | 1024 MB |
| 1 TB | 1024 GB |

> 注意：内存/文件大小按 **1024** 进制；硬盘厂商常用 1000 进制，所以标称容量与系统显示会有差异。

### 与 C++ 类型的关系

| 类型        | 常见字节数 |
| --------- | ----- |
| char      | 1     |
| int       | 4     |
| long long | 8     |
| float     | 4     |
| double    | 8     |
| bool      | 1     |

### n 位二进制能表示的范围

* 无符号：`0 ~ 2^n - 1`
* 有符号（补码）：`-2^(n-1) ~ 2^(n-1) - 1`

例如 8 位有符号整数范围是 `-128 ~ 127`，32 位 int 范围约 `-2.1×10⁹ ~ 2.1×10⁹`。


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