Select Show > File name extensions. ... If Excel is not set as the default application to open the Excel file types (.xls, .xlm, .cvs, etc.), the file may open in another application.

To show what this means, if you have a file called test.doc.txt, Windows will only display test.doc. From this filename, you would then assume this is a Word document, but when you double-click on ...

You can find a simple File Name Extensions check box on the View tab, in the Show/Hide group. If you use this setting regularly, there's an even faster way to toggle extensions on or off without ...

Show or Hide Extensions for All Files in iOS. Since iOS 11, Apple's Files app has made file management a more realistic proposition on ‌iPhone‌ and ‌iPad‌.

If the DAT file you're trying to open is text, you can convert the file into text in the Microsoft Excel program by first saving it as a CSV file. Right-click the DAT file on your PC and click "Open." ...