C program to calculate area and perimeter of a circle has been given below. Suppose, the radius of a circle is r unit, the area and perimeter of that circle would be (pi * r^2) unit^2 and (2 * pi * r) unit, respectively. The approximate value of pi is 3.141592.
For example, if the radius of a circle is 5 cm, then area of the circle would be (pi * 5^2) = 78.54 cm^2 while perimeter would be (2 * pi * r) = 31.42 cm.
The algorithm, pseudocode, and time-complexity of the program have also been covered below.
1. Algorithm to calculate area and perimeter of a circle
1. Take the radius r of a circle as input.
2. Compute a = pi * r^2
3. Compute p = 2 * pi * r
4. Declare a as the area and p as the perimeter of that circle.
2. Pseudocode to calculate area and perimeter of a circle
Input : Radius r of a circle
Output : Area A, Perimeter P of the circle
1. Procedure areaPerimeter(r):
2.
3.
4.
5. End Procedure
3. Time complexity to calculate area and perimeter of a circle
Time Complexity: O(1)
4. C Program & Output to calculate area and perimeter of a circle
/***************************** alphabetacoder.com C program to calculate area and perimeter of a rectangle ******************************/ #include <stdio.h> #define pi 3.141592 int main() { // declare variables float r, a, p; // take input printf("Enter the radius of a circle: "); scanf("%f", & r); // calculate area a = pi * r * r; // calculate perimeter p = 2 * pi * r; // display result upto 3 decimal places printf("Area: %0.3f\n", a); printf("Perimeter: %0.3f\n", p); return 0; }
Output
Enter the radius of a circle: 6
Area: 113.097
Perimeter: 37.699