Files are used to store different types of information such as documents, images, videos, audio, and spreadsheets. Understanding file types and extensions helps users identify files, choose the right software to open them, and manage computer data efficiently.

1. What is a File?

A file is a collection of digital information stored on a computer or other device. Each file usually has a name and a file extension that indicates its format.

Example:
Student_Record.xlsx

Here, Student_Record is the file name and .xlsx is the file extension.

2. What is a File Extension?

A file extension is the set of characters after the dot (.) in a file name. It helps the operating system and applications identify the type of file.

Examples:

• .docx – Microsoft Word document
• .xlsx – Microsoft Excel workbook
• .pptx – PowerPoint presentation
• .pdf – PDF document
• .jpg / .png – Image files
• .mp3 – Audio file
• .mp4 – Video file
• .txt – Text file
• .zip – Compressed file

3. Common File Types

4. Opening Files with the Correct Application

Different file types are normally opened using different applications.

Examples:

• .docx → Microsoft Word
• .xlsx → Microsoft Excel
• .pptx → Microsoft PowerPoint
• .jpg → Photos/Image Viewer
• .mp4 → Video Player
• .pdf → PDF Reader or Web Browser

5. Changing File Extensions

Users should be careful when changing a file extension manually. Simply renaming .jpg to .pdf, for example, does not convert the file into a PDF.

To properly change a file format, use the application’s Save As, Export, or Convert option.

6. Identifying Unknown Files

Before opening an unknown file, check:

• File name and extension.
• Where the file came from.
• Whether the sender or source is trustworthy.
• Whether antivirus/security software identifies any risk.

Avoid opening suspicious files, especially unexpected executable files such as .exe.

Practical Activity

Students can practice by:

1. Creating a Word document and saving it as .docx.
2. Creating an Excel workbook and identifying .xlsx.
3. Saving a presentation as .pptx.
4. Identifying image, audio, video, and PDF extensions.
5. Checking file properties.
6. Organizing different file types into appropriate folders.