Anyone who has experimented with the Linux operating system will be familiar with ISO files but even if you haven’t ventured down this route, it’s possible that you’ve heard the term. But what are these files and what purpose do they serve?

A good way to think of an ISO file ­ whose name derives from the International Organization for Standardization ­ is as a disc image, because it contains the entire contents of a CD or DVD within a single file like taking a ‘snapshot’ of the disk.

In much the same way that a compressed file such as a ZIP can contain hundreds or even thousands of files, an ISO is simply a container for many files. Importantly, though, it is an exact replica of the original disc it represents. In this Masterclass we’re going to look at the various uses for ISO files and the tools needed to work with them.

The ISO format is most commonly used as a means of software distribution via the internet. As already hinted, it is often used to package up a version of Linux into a single big file that can be downloaded and, often, saved straight to a disc.

Rather than making the individual files on a CD or DVD available for download, or supplying software on a physical disc, it is generally cheaper, easier and more reliable for companies to use this method to transfer large volumes of data.

The benefits of this method over transporting discs are obvious ­ not only are there no postage costs involved, but there is no risk of a disc being lost or damaged in transit. It is also quicker and simpler to download one big file than lots of individual files.

Why use ISO files?
Once an ISO file has been downloaded there are two possible routes to go down. The first option is to burn the file onto CD or DVD in order to access the files it contains; the resulting disc can then be used in precisely the same way as any other CD or DVD. The alternative is to use image-mounting software to convert the image file into a virtual disc that can then be loaded into a virtual optical drive and used as if it was a real disc.

The ISO format is also useful for the purposes of backing up data. With most modern PCs fitted with recordable CD or DVD drives, many people use these to create backups of important data. Having one backup copy of files is all well and good but more than one is advisable. Rather than wasting space by storing multiple copies of the same CDs and DVDs, discs can quickly and easily be converted into ISO images, which can then be stored on a hard disk.

Of course, storing ISOs on a hard disk isn’t a fail-safe backup method ­ it’s an additional measure, not a substitute. A better use for ISO files might be to store backup copies of all your commercial software CDs and DVDs on the hard disk: this has the added benefit of giving access to these titles without having to reach for the original CD or DVD. We’ll come to this soon.

Making an ISO file
A computer that is fitted with a recordable drive will usually have disc-burning software, such as Nero, installed. Such programs can often be used to create ISO files.

In the case of Nero, launch the program and insert the CD or DVD that is to be converted into an ISO file. Now click on the Extras menu and select Save Tracks before selecting ‘ISO image file (*.iso)’ from the dropdown menu labelled ‘Output file format’. Click on the Browse button to choose a folder in which to save the file and then click on Go to begin the process. While Nero is capable of creating ISO files using this method, it is a little convoluted.