Printer apparatus that conveys printing paper by set feeding amount and set back-feeding amount

A printer apparatus comprising:

• a print head for printing on printing paper;
• a casing that includes a paper ejection port for ejecting printed printing paper;
• an attachment that includes a paper ejection port for receiving the printing paper ejected from the casing and then ejecting the received printing paper and is attachable to and detachable from the paper ejection port of the casing;
• a conveying device that conveys the printing paper after printing in forward rotation to eject the printing paper from the paper ejection port of the attachment and conveys the printing paper in reverse rotation for next printing;
• an information acquisition processor that acquires information of a distance from the paper ejection port of the casing to the paper ejection port of the attachment;
• a setting processor that
• sets, in accordance with the acquired information of the distance, a distance obtained by adding a distance that the printing paper passes through the attachment to a distance between the print head and the paper ejection port of the casing as a feeding amount of the printing paper after printing when ejecting the printing paper after printing from the paper ejection port of the attachment, and
• sets, in accordance with presence or absence of a head-up function of moving the print head between a first position where printing on the printing paper is available and a second position where printing on the printing paper is not available, a back-feeding amount when conveying the printing paper ejected from the paper ejection port of the attachment to a position for next printing in reverse rotation;
• and
• an engine control processor that
• causes the conveying device to convey the printing paper in forward rotation by the set feeding amount to eject the printing paper after printing, and
• causes the conveying device to convey the printing paper in reverse rotation by the set back-feeding amount to return the printing paper to a next printing position before next printing.