A printing apparatus comprising: a printing fluid cartridge; and a cartridge mounting portion to which the printing fluid cartridge is configured to be mounted, the cartridge mounting portion comprising: at least one contact configured to be electrically connected to at least one electrical interface (75, 76, 77) of the printing fluid cartridge; an optical sensor (114, 116) configured to detect a light attenuating portion (33, 88, 89) of the printing fluid cartridge, and an engagement member configured to retain the printing fluid cartridge in the mounted position; wherein the printing fluid cartridge comprising: the at least one electrical interface (75, 76, 77) configured to allow an electrical access to an integrated circuit provided to the printing fluid cartridge and configured to be electrically connected to the at least one contact; the light attenuating portion (33, 88, 89) configured to be inserted between a light emitter and a light receiver of the optical sensor and to be detected by the optical sensor, wherein the light attenuating portion is configured to provide information as to the presence of the printing fluid cartridge in the cartridge mounting portion or a type of the printing fluid cartridge by attenuating light of the optical sensor, and an engagement portion configured to contact the engagement member of the cartridge mounting portion in an inserted state and to push the engagement member in an opposite direction of the insertion direction, a printing fluid cartridge; and a cartridge mounting portion to which the printing fluid cartridge is configured to be mounted, the cartridge mounting portion comprising: at least one contact configured to be electrically connected to at least one electrical interface (75, 76, 77) of the printing fluid cartridge; an optical sensor (114, 116) configured to detect a light attenuating portion (33, 88, 89) of the printing fluid cartridge, and an engagement member configured to retain the printing fluid cartridge in the mounted position; wherein at least one contact configured to be electrically connected to at least one electrical interface (75, 76, 77) of the printing fluid cartridge; an optical sensor (114, 116) configured to detect a light attenuating portion (33, 88, 89) of the printing fluid cartridge, and an engagement member configured to retain the printing fluid cartridge in the mounted position; wherein the printing fluid cartridge comprising: the at least one electrical interface (75, 76, 77) configured to allow an electrical access to an integrated circuit provided to the printing fluid cartridge and configured to be electrically connected to the at least one contact; the light attenuating portion (33, 88, 89) configured to be inserted between a light emitter and a light receiver of the optical sensor and to be detected by the optical sensor, wherein the light attenuating portion is configured to provide information as to the presence of the printing fluid cartridge in the cartridge mounting portion or a type of the printing fluid cartridge by attenuating light of the optical sensor, and an engagement portion configured to contact the engagement member of the cartridge mounting portion in an inserted state and to push the engagement member in an opposite direction of the insertion direction, the at least one electrical interface (75, 76, 77) configured to allow an electrical access to an integrated circuit provided to the printing fluid cartridge and configured to be electrically connected to the at least one contact; the light attenuating portion (33, 88, 89) configured to be inserted between a light emitter and a light receiver of the optical sensor and to be detected by the optical sensor, wherein the light attenuating portion is configured to provide information as to the presence of the printing fluid cartridge in the cartridge mounting portion or a type of the printing fluid cartridge by attenuating light of the optical sensor, and an engagement portion configured to contact the engagement member of the cartridge mounting portion in an inserted state and to push the engagement member in an opposite direction of the insertion direction,