Image forming apparatus with multiple cassettes and determination portion to determine a prohibited operation

An image forming apparatus, comprising:

• an image forming portion configured to form an image on a sheet;
• a connection portion to which a first optional device and a second optional device are selectively detachably connectable;
• and
• a determination portion configured to determine whether to prohibit an operation of the image forming apparatus,
• wherein the first optional device is connectable to the connection portion of the image forming apparatus,
• wherein the first optional device is connectable to another first optional device so that a plurality of first optional devices are stacked and connectable to the image forming apparatus,
• wherein the second optional device is installed on a floor and is connectable to the connection portion of the image forming apparatus or the first optional device,
• wherein in a case in which the second optional device is not connected to the image forming apparatus and a number of the first optional devices connected to the image forming apparatus is larger than a first threshold value, the determination portion prohibits the operation of the image forming apparatus, and
• wherein in a case in which the second optional device is connected to the image forming apparatus and the number of the first optional devices connected to the image forming apparatus is larger than a second threshold value, the determination portion prohibits the operation of the image forming apparatus.