Developing cartridge capable of reducing size of image forming apparatus

A developing cartridge comprising:

• a casing configured to accommodate developer therein, the casing extending in a first direction;
• a roller rotatable about a first axis extending in the first direction, the roller including a roller shaft extending in the first direction, the developer on an outer peripheral surface of the roller;
• a coupling rotatable about a second axis extending in the first direction, the coupling being positioned at one side of the casing in the first direction;
• a detection protrusion movable according to rotation of the coupling, the detection protrusion being positioned at another side of the casing in the first direction;
• an electrode electrically connected to the roller shaft, the electrode being positioned at the another side of the casing in the first direction;
• and
• a storage medium including an electric contact surface, the electric contact surface being positioned at the one side of the casing in the first direction, the electric contact surface being spaced apart from the coupling.