FFirmware
Firmware is a read only set of instructions that is embedded in a hardware device to either add or improve function. Sometimes there are two parts to a Nikon firmware update labeled A or B. Some updates will perform either A or B, and some will perform A and B, only one at a time. Some others still will perform both A and B at the same time. Please read the instructions carefully as firmware updates are permanent and cannot be 'undone' outside of the service department. Newer firmware versions will overwrite older versions and will also include all previous update changes.