A circle is one of the simple shapes of Euclidean geometry. It is the locus of all points in a plane at a constant distance, called the radius, from a fixed point, called the center. Through any three points not on the same line, there passes one and only one circle.

A diameter is a chord passing through the center. The length of a diameter is twice the radius. A diameter is the largest chord in a circle.

Circles are simple closed curves which divide the plane into an interior and an exterior. The circumference of a circle is the perimeter of the circle, and the interior of the circle is called a disk.

## Sample Shell Script To Calculate Area and Circumference of Circle

#!/bin/bash # Shell script to calulate area and Circumference of circle. # It take radius of a circle as input. # ------------------------------------------------------------------------- # Copyright (c) 2005 nixCraft project <http://cyberciti.biz/fb/> # This script is licensed under GNU GPL version 2.0 or above # ------------------------------------------------------------------------- # This script is part of nixCraft shell script collection (NSSC) # Visit http://bash.cyberciti.biz/ for more information. # ---------------------------------------------------------------------- # Lesson on Circumference of a Circle : # Visit http://www.mathgoodies.com/lessons/vol2/circumference.html echo -n "Enter the radius of a circle : " read r # use formula to get it area=$(echo "scale=2;3.14 * ($r * $r)" | bc) # use formula to get it d=$(echo "scale=2;2 * $r"|bc) circumference=$(echo "scale=2;3.14 * $d"| bc) echo "Area of circle is $area" echo "Circumference of circle is $circumference"