How to know the format of the file WinXP system hides or displays the file format method

stores various types of files on the computer, each type of file requires a corresponding application to open the operation, and how do we know the format of the file? Xiaobian here is an example of XP system, telling everyone how to view the format of the file?
1. Double-click to open any folder (the small file is open d disk), click "tools" in the toolbar, Select "Folder Options" as shown below.
Folder Options
2. Switch to the "View" tab, remove the checkmark in front of "Hide Extensions for Known File Types" and click the OK button to save and exit.
View
3. After the completion, you can clearly see that the file's suffix name is displayed, which is the file format.
File Format
If you need to re-hide, check the second step to remove the check and click Save again.