Image forming apparatus having a detachably mountable image forming unit

An image forming apparatus, which carries out an image forming process with a detachably mountable image forming unit mounted thereon, said image forming apparatus comprising:

• a mount detecting portion, which detects whether the image forming unit is mounted;
• a discriminating portion, which discriminates, when a mounting of the image forming unit is detected by said mount detecting portion, whether the mounted image forming unit is new;
• an information holding portion, which holds unit control information corresponding to the image forming unit;
• and
• an information updating portion, which updates the unit control information held by said information holding portion, based on discrimination results from a previous detection and a current detection by said discriminating portion,
• wherein when the discrimination result based on the previous detection by said discriminating portion is not new and the discrimination result based on the current detection by said discriminating portion is new, the information updating portion backs up the unit control information corresponding to the image forming unit at the previous detection held by said information holding portion,
• when the discrimination result based on the previous detection by said discriminating portion is new and the discrimination result based on the current detection by said discriminating portion is not new, the information updating portion updates the unit control information so that the previously backed-up unit control information corresponds to the image forming unit at the current detection, and
• wherein when the discrimination result based on the previous detection and the discrimination result based on the current detection by said discriminating portion are the same, said information updating portion maintains the unit control information held by said information holding portion.