Game port
Certain applications and games are  able to use some analog joysticks even without explicit calibration, under certain restricted conditions. A system of a joystic and game port that is not calibrated can give a "direction", at best. It can not give an intensity. For this setup, an analog joystick can be "self calibrated" just by leaving the joystick in the middle position and taking a measurement, and then using some arbitrary or adaptive threshold to detect movement and excursion from the middle position. The limitation of this method is that the reading of the same joystick over the same game port can change over time, and some joysticks cannot work at all with this method. Also, the joystick must be in the middle position at least once when the implicit "self calibration" takes place, even if this is not directly stated.