> 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/computer-basics/type-conversion.md).

# 数据类型转换

### 为什么需要转换

不同数据类型之间进行运算或赋值时，会发生类型转换，分为**隐式转换**和**强制转换**。

### 隐式类型转换（自动）

按照“由低到高”的方向自动进行，不会丢失精度：

```
bool → char → short → int → long long → float → double
```

```cpp
int a = 3;
double b = a;      // int 自动转 double，3.0
cout << 5 / 2.0;   // 2.5，int 与 double 运算，int 转为 double
```

### 强制类型转换（显式）

当需要把高精度转成低精度，或控制计算方式时使用：

```cpp
int a = 7, b = 2;
cout << a / b << endl;              // 3，整数除法
cout << (double)a / b << endl;      // 3.5，先转 double

double x = 3.9;
cout << (int)x << endl;             // 3，直接截断取整，不四舍五入
```

> 常见坑：`5 / 2` 结果是 2 而不是 2.5，因为两个整数相除结果是整数。需要写 `5 / 2.0` 或强制转换。


---

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