The extension of notepad is:

🧠 Explanation:

The extension for Notepad files is .txt, indicating plain text documents. These files store unformatted text, compatible across platforms, used for notes, coding, or data storage. Understanding file extensions is crucial in computing, as they denote file types and guide software compatibility. The .txt extension ensures simplicity, making it ideal for basic text editing in programming or documentation. Its universal readability supports applications in IT, education, and data management, ensuring seamless file sharing and editing across devices and operating systems for various technical and non-technical purposes.