file extensions connect files to the right programs by telling the computer which program to use to open your files!
When you hear things in trainings like ‘.swf’ or ‘.jpg,’ those are file extensions. Some have even become part of our regular vocabulary without many even knowing that they’re talking about a file extension! An .mp3, for example, is a type of file, even though now the word is becoming synonymous with ’song.’
What is it, and what does it do? This is important. A file extension tells your computer what file type it’s dealing with so it knows what program it should use to open a file. For example, can you imagine opening an .mp3 in Microsoft Word? It just wouldn’t work.
If you open a file in microsoft word, you’re opening a .doc file. It gets confusing when a program opens and uses a bunch of different file extensions.
For example, why do we need .mov, .avi, .flv, etc… they’re all video types, right? Why do we need .wav and .mp3? They’re all audio, right? Yes, but the difference is size in those examples. A song in .wav is a different than the same song saved as a .mp3. Imagine a piece of data is the size of a marble. A file is made up of a bunch of data. If you filled an entire classroom full of marbles and called it a song file, that would be size of a song as a .wav. If you put a few marbles in a mason jar, you’d have the size of the song as an .mp3. Now you’re seeing the advantage of using different file types, right? File extensions indicate the file type -that’s important.
How many file types are there? Hundreds, so don’t bother trying to learn them all. The good news is that there are way fewer that you’ll actually have to worry about, and most, you’ll find, you already know! In the comments below, I’m going to start a list of common file types. I’m hoping folks will help out by listing file types they run into in virtual education with ’the skinny’ on each file type. If we get a big enough list, I’ll compile it to a table and share it!
May 29th, 2009 at 1:30 pm
Here’s a bit to get the list started:
1. .doc – this is the file extension for a file created by Microsoft Word, the most popular word processing software. The most recent version of Microsoft Word is OOXML-based and has the filename extension of .docx
2. .jpg – this is the filename extension for the compressed graphic format standardized by the JPEG (Joint Photographic Experts Group). Most digital images we see in the internet and in computers are in the JPEG format and has the filename extension of .jpg. This file can be viewed in most image viewing and editing software.
3. .exe – this is the extension for Windows or DOS executable programs. If a file has this extension, it is a program and runs when opened. Self-extracting archives also have this extension.
4. .htm or .html – the extension for HTML web page. HTML stands for “Hyper-Text Markup Language”, the language used in writing web pages. This very page you are looking at now is a web page with a filename extension of .htm.
5. .mp3 – the filename extension for compressed audio format developed by the Moving Picture Experts Group. This audio format is very popular nowadays because its size is many times smaller than that of the Wave or AIF file. This makes it easy for people to download music from the internet. The downside of .mp3 is that the quality of sound is not as good as that of the Wave or AIF file.
6. .mpg – this is a video format standardized by the Moving Picture Experts Group (MPEG). This file can be played using Windows Media Player, Winamp, Roxio Easy Media Creator, Apple QuickTime Player, or VLC Media Player.
7. .zip – this is the extension for any file that is compressed using the ZIP compression, a kind of compression which allows every file in the archive to be compressed separately. Programs that can open .zip files include WinZip, PKZip, and the popular WinRar.
8. .pdf – this is the file extension for the document created by Adobe Acrobat or other PDF producing programs. PDF stands for “Portable Document Format” and may contain images, texts, forms, outlines, and links. PDF files are usually created from another file, like a web page or a Word document.
9. .xls – this is the filename extension for Microsoft Excel Spreadsheet created with Microsoft Excel, the most popular spreadsheet program.
May 29th, 2009 at 5:37 pm
You might want to add to this list:
http://en.wikipedia.org/wiki/Microsoft_Office_2007_file_extensions
May 30th, 2009 at 12:37 am
It’s helpful to have this resource to file suffixs, providing a brief description for each. In using Microsoft Office 2007, the x added to files, whether it be doc, ppt, or xls (becoming docx, pptx, xlsx), I’ve discovered that the majority of recipients receiving MS 2007 file types are unable to open the files, so the recommendation is to be sure to rename the file without the ending x. Perhaps there is a more efficient way to work around this until MS 2007 becomes more popular. ~Connie J.
June 13th, 2009 at 8:47 pm
Great post! I’ll subscribe right now wth my feedreader software!
July 12th, 2009 at 11:46 pm
Hey!, I am glad I pressed harder enough until I found roxio easy media creator 9, because this post on Knowledge Nugget I -File Extensions was extremely helpful. Just last Sunday I was pondering on this quite a bit.
September 14th, 2009 at 4:41 pm
I have come across some files on a cd rom with the .imj extension. I assume they are graphics files but nothing I have will open them. any suggestions and/or help??
November 19th, 2009 at 6:48 am
Hello Joe Becker,
.imj files are indeed image files, this particular file extension relates to screen savers.
you can usually open this file by changing the .imj to a .JFIF or .BMP
Pegasus Image Corporation software will open this .imj file though on its own, if you can find it on the internet somewhere, your in good luck. CYA.
November 19th, 2009 at 6:50 am
http://www.accusoft.com/
for .imj
try to find the program on there!