What is a file extension?

We received an urgent call from a client who had been sent an image from a friend but they were not able to view the photograph. The customer told us that the image file was a white icon with a name and when they double clicked it an error message appeared asking what programme should be used to open the file.

After travelling to the customer’s home we saw that the image was missing a crucial piece of information that tells the computer what type of file it is. This information is what is shown to the right of the dot at the end of the file name and this is known as a “file extension”. The client then asked us “what is a file extension”? We answered by telling him that it is a three letter computer file abbreviation that tells the computer what the file is and therefore what programme that is registered by the computer that is required to open the file so that it can be worked on. For example, a “.doc” tells the computer that the file is a Microsoft Word document. There are numerous file extentions such as “.xls; .pdf; .ppt; .gif; .bmp; .tiff; .mp3” etc.

To resolve the probem with this particular case,  because the customer knew that the file was an image, we guessed that it was a “.jpg” image and after appending the “.jpg” to the end of the image’s file name by using the Windows “rename” tool, the customer was then able to view the photograph.

Sometimes, you may be sent a file by someone that cannot be opened because the programme required to open the file is not installed on your computer. In this case, you need to ask the sender of the file for the name of the programme that was used to create the file, so that you can then install this programme on your computer in order to open it successfully.

For more information please look at this Hubpage article: