What is the purpose of the donut function in the AutoLISP language?

In AutoLISP language, the donut function is used to create a solid or hollow ring (also known as a doughnut). It takes the following parameters: 1. Center point coordinates: specifying the center position of the ring. 2. Inner radius: specifying the inner radius of the ring. 3. Outer radius: specifying the outer radius of the ring. 4. Entity flag: used to determine if the ring is solid or hollow. The donut function can create a ring entity in AutoCAD, which can be used to draw various ring shapes, such as pipes, tires, etc. It provides a convenient way to create and manipulate these shapes.