1. In **Solution Explorer**, select the file you want to compile as a header unit (in this case, `Pythagorean.h`). Right-click the file and select **Properties**.

1. Since this is a header file, set the **Item Type** property to **C/C++ compiler**. By default, header files have an **Item Type** of **C/C++ header**. This property also sets **C/C++** > **Advanced** > **Compile As** to **Compile as C++ Header Unit (/exportHeader)**.

**Compile a source file as a header unit**:

If you want to compile a file that doesn't have an *`.h`* or *`.hpp`* extension as a header unit, set the **Compile As** property to **Compile as C++ Header Unit (/exportHeader)**.