Firmware: Camera operating system
An EOS camera is a mini-computer, complete with its own operating system. This system controls many of the functions within the camera. The operating system software is called ‘firmware’, because it does not change in use. It is stored in read-only memory (ROM) and is retained when the camera is switched off.
From time to time, Canon makes changes to the operating system. These changes are supplied to users as firmware updates. Firmware updates are released for a variety of reasons – sometimes it’s to fix bugs and glitches in the operation of the camera, sometimes it’s to add extra features.
For example, in an EOS 30D update, there is a new menu option when using direct print which allows you to select semi-gloss paper in the camera settings, as well as a bug fix that stops the camera reporting the wrong number of remaining shots in the viewfinder during continuous shooting.
When you download the latest firmware version, it covers any previous updates as well, so you don’t need to worry if you have missed any intermediate updates – you will automatically gain all the benefits.
Whether you need to update or not is down to you. If the update has a bug fix, then it is probably worth installing to make sure your camera is running in optimum condition. If however, it only adds some extra features that you may never use, like the paper setting for direct print in the EOS 30D, then you might consider skipping it as you will gain nothing by updating.