Cylindricity

It sets a form limit for a cylindrical surface. The zone lies between two coaxial cylinders, with a radial gap equal to the value in the feature-control frame (the boxed tolerance entry).

Use it for a shaft, pin, or bore. It controls shape, not location from a datum, a reference used to position or orient other features.

How did the notation reach CAD?

Through a sequence of drawing standards. The broader GD&T lineage reaches the U.S. military standard MIL-STD-8 (1949), which set drawing rules for dimensioning and tolerancing. The U.S. Y14.5 standard carried that language forward; its 1973 revision addressed electronic manufacturing. By 2009, it covered computer-aided design (CAD).