(computing) built-in function

being busy / being multipurpose / frequent usage, heavy use

use heavily

a program (leaflet listing information about a play, game or other activity) / (broadcasting) a program (performance of a show or other broadcast on radio or television)

(computing) program (to write code, to enter a program or other instructions into a computer); event schedule

(mathematics, computing) function

(mathematics) inverse function

(trigonometry) a trigonometric function

(calculus) derived function - of a function, another function, the value of which for any value of the independent variable is the instantaneous rate of change of the given function at that value of the independent variable.

real variable function