实现简单的记事本功能，功能精简实用，使用简便-Simple notepad function, streamline the utility, ease of use

本代码运用C#实现笔记本的基本功能，例如字体字号的改变，加粗加黑的变换，实现打印功能-The code to use C# to achieve the basic functions of the notebook, such as changing the font size, bold with black transform, printing