About Extensions

No, we will not be talking about hair or hair make up, although that may also be very interesting.

We will be discussing computer file extensions. This is one of those things that you’ve probably came across hundreds of times but never noticed. Almost all files on your computer have an extension.
This extension is whatever follows to the last . of a file name. For instance, you can find a file on you computer that is called notepad.exe. The .exe is the extension of the file. This tells the operating system what type of file this is, for instance, in this case it is an executable file.

The most common extensions are .TXT (text file), .DOC (word file), .LNK (shortcut), etc. If you are not an advanced computer user, chances are that you have never noticed this. The reason for this is simple. Windows, for example, hides the extension of all “known” files. So if windows knows what to do with a file, it won’t show the extension any longer. Mac for instance does this too.
I’m guessing that this is a security measure, since you can change the extension of a file to anything. Which can be dangerous sometimes. If a program is, for example, looking for a file options.dll, but you’ve changed it to options.exe, the program will not work any longer, since it seems that the file is gone. So it’s best to leave file extensions for what they are.

You may wonder why I’m telling you all this, since you better don’t touch the extensions. It’s because the use of extensions is one of the oldest tricks in the book to get a virus on you computer. Many malware developers will create a file that is, for instance, named sales_report.xls.exe. They want you to think it is an excel (.xls) file but in reality it’s an executable (.exe) file. Remember, the extension is whatever follows to the last . of a file name.
You would be amazed how often this works, simply because there are a lot of operating systems that hide the extensions. Of course you can always enable file extensions. (We’ll get back to that in a later post)

Bottom line, always be careful ;-).


One thought on “About Extensions

  1. Pingback: Backward Compatibility – ytilibitapmoC drawkcaB | Tech-o-rama

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