A file extension is an extended name for file base on its format or its contents for examples .exe, .rar, .pdf and many more. Windows 7 hide the file extension by default so if you open your Windows explorer, you will see just a file name without extension. For common file that you open usually, I think no problem it you leave it hidden as default but sometime you have a file from someone or download it from internet before open it you should know about its extension.
Knowing file extensions will help you how to open it or sometime if you don’t know its extension it is better not to open it(possible harmful file). As example most of you should know that doc or docx file must associate with Microsoft Word and exe file can run with double click. So to know file extension you must view it and here I will share you how to show file extensions in Windows 7:
1. Right click on Start button and click Open Windows Explorer.
2. Press ALT from your keyboard to show hidden explore bar.
3. Click Tool menu or press t from your keyboard.
4. Click Folder Options or press o from your keyboard.
5. Folder Options window will appear.
6. Click View tab.
7. Uncheck Hide extensions for known file types.
8. Click Apply and Ok to save new configuration.
To prove it just view your Windows explorer and surely you will find every file name complete with its extension. When you want to hide file extension just access Folder Option and check Hide extensions for known file types back. Enjoy it!