What is a file extension?

A file extension is the suffix you'll see at the end of a filename, and it's this little assortment of letters that tell you, and your computer, what kind of file it is and what program should be used to open that file.

We've taken a look at some of the most important file extensions and created a simple explanatory guide for you, to help you identify, locate, and execute any file extension.

Files Aplenty

If you had a look on your computer, you'd probably notice that you have lots of different types of files stored on your hard drive – text documents, photos, e-mails, and music. These are all different types of files, so it would make sense that they have different types of file extensions, too.

Picture perfect files

Common image file extensions:

Image formats are usually separated into two broad categories - lossy and lossless compression formats. Lossless image formats preserve the image exactly how it was originally saved, and usually these are your PNG, BMP, GIF, TIFF files.

Lossy images are compressed and some detail from the original gets lost in the process, and a prime example of this type of file is a JPEG.

What are the differences between these file formats?

PNG files support a wider range of formats from 8 bits per pixel to 24 bits per pixel. Useful for: its flexibility and compression efficiency so can be e-mailed, archived or uploaded to the Internet.

BMP files are larger as they're not compressed. Useful for: not much.

GIF formats support only 256 colours (8 bits per pixel) including transparency, as well as animation. Useful for: uploading pictures to websites and for e-mailing, as the file sizes are so small.

JPEG (also JPG) compresses your image by discarding details that are typically too insignificant for the human eye to detect. Useful for: compressing images that have lots of complexity in them with similar colours throughout

TIFF formats support a wide range of pixel formats with zero compression for lossless editing. Useful for: photo-editing and high-resolution photographs.

Lossy compression formats are generally used for photographs and so these file types are not suited for drawings, illustrations or text, as the process used to compress these files means that not all of the file information is encoded, so when it is opened as an image, it's not an exact representation of the original image. The advantages of lossy compression is a reduction on file size, so you'll be using this format for e-mailing pictures, or uploading images on the Internet.

Lossless compression formats are suited for illustrations, drawings, text and other media, as lossless compression encodes all the information from the original, so when the image is decompressed, it will be an exact representation of the original. As there is no loss of information compression of file sizes will remain rather large, so you'll probably be using these file formats for high-resolution print-quality photographs or designs.

How to change the file format of any image:

1.  Locate your image file and open it with the appropriate program.
2. Select File | Save As and at the bottom of the dialogue box, you should see a dropdown menu with options for File Formats.
3. Choose which type of file you'd like to save it as, and select Save.

Text heavy files

Common document file extensions:

Text file formats like RTFs and TXTs are useful for purely textual documents, so you might want to use these files for note-taking or dictation, while Microsoft Word documents can contain pictures, graphs and other media with formatting and layout changes, making it perfect for assignments and business documents.

Question: I was e-mailed a document (.docx) the other day, and I tried to open it, but it won't open with my Microsoft Word 2003. What should I do?

Answer: You need to download the Microsoft Office Compatibility Pack for Word, Excel, and PowerPoint File Formats. The Compatibility Pack works with Microsoft Office 2000, Office XP, or Office 2003, allowing you to you open, edit, and save files using the file formats in newer versions of Word, Excel, and PowerPoint. All you need to do is go to the Microsoft Website and search for "Microsoft Office Compatibility Pack" and follow the download instructions.

Audio files:

Common audio file extensions:

These are the types of audio file types you should be familiar with if you are planning to download music off the Internet or even copy a CD.

WAV files are a common file format and they're defined as lossless, meaning that files are large and complete and nothing has been lost. MP3 files are compressed WAV files and they're useful for creating and storing playlists on iPods and the like.

WMA files are the equivalent of the MP3 format for Windows Media Player and Microsoft claims that the WMA files are compressed three times more than MP3s, but that they still retain their original sound quality.

Question: I have a lot of photos that I'd like to e-mail to someone, but I don't want the e-mail size to be too big, what should I do?

Answer: you need to compress the files into a folder and send them so they can be unzipped on the other side.

How to compress files:

Windows -

1.  Locate the file or folder to be compressed.
2. Right click the file or folder and scroll down to Send To and then Compressed (zipped) Folder.
3.  Upload the compressed file as an attachment to your email.

How to unzip the compressed files from the folder:

You'll need to use the Extraction Wizard:

1.  Double-click the compressed folder to open it. The Extract all files command appears in the Folder Tasks list.
2. Click Extract all files to start the Extraction Wizard, and then click Next to start the extraction process.
3. When you are prompted to select a location to put the extracted files, select a location, and then click Next. By default, Show extracted files is selected.
4.  Click Finish to view the extracted files.

Mac –

How to compress files:

1.  Highlight/select the files you'd like to compress and right click on them.
2. Select Compress These Items and wait for a zipped folder to appear, indicating that the task has been successfully performed.

How to unzip compressed files:

You'll need to use StuffIt Expander:

1. locate the zipped folder you've just downloaded.
2. Double-click on the icon, and the files contained within the zipped file will be automatically unzipped into the same folder as the original zip file.

File extensions and managing your computer's filing system is not that difficult. And if you ever come across a file extension that you're unsure of, all you need to Google is "how to open _____ file" and you should be able to figure it out from there.

Digital filing? Dusted.