Pointing stick
A pointing stick is a pointer, i.e. a device used to point, in the form of a stick.
Original
The old-fashioned pointer is simply a long, slender, often flexible stick made in a strong material, designed to indicate places on maps, words on blackboards etc., as still commonly used in classrooms.
In addition it may be used as any ordinary sticks for other purposes, e.g. for punitive caning (compare rulering).
Input hardware
The pointing stick (trademarked by IBM as the TrackPoint) or "nubbet" as it it less comonly known, is a pointing device (compare especially Touchpad) for laptops invented by research scientist Ted Selker and is present on many brands of laptop, including IBM's line of ThinkPad laptops (now made by Lenovo) and Dell Latitudes. It has also been observed on computer mice, in blue or red.
The pointing stick has a replaceable colored tip which is often referred to as the cap or the nipple. On a QWERTY keyboard, the stick is embedded between the 'G', 'H' and 'B' keys, and the mouse buttons are placed just below the Spacebar.
The pointing stick operates by sensing applied force (hence it is also known as an isometric joystick), typically by measuring the resistance of a material. The velocity of the cursor depends on the applied force. The Trackpoint III and the Trackpoint IV has a feature called Negative Inertia that causes the cursor's velocity to "overreact" when it is accelerated or decelerated. Usability tests at IBM have shown that it is easier for users to position the cursor with Negative Inertia enabled than it is with the feature disabled.
Cursor drift is an ubiquitous problem among pointing sticks, owing to frequent recalibration. However, ThinkPoints automatically recallibrate when the stick recognizes a steady cursor drift.
The pointing stick seems to be declining in deployment, to the dismay of those who find it to be preferable to either mouse or touchpad. It is especially liked by touch-typists because it is the only pointing device which does not require the user to remove their fingers from the home row.