How to show or hide file extension?

Everyone working with files in their computer. But they need to know what type of file they are working .How they know that. By file extension they know which file they are working.

If you are working with an image file its file extension will be aftab.jpg or aftab.png etc like that. This .jpg or .png is called file extension. Showing or hiding file extension is very important.How you can do this.
First go to windows start menu. Than go to control panel. Than go to file options. Click file options. File extension popup menu appears. Than go to view tab. Than uncheck Hide extensions for known file types. Than all file extension of files will be appears in your computer. If you check the Hide extensions for known file types option than all files extension will be hide. This way you can show or hide file extension of your computer.