C language tutorial

Write a C program to enter radius of a circle and find its diameter, circumference and area.
/*
diameter = 2 r
circumference = 2 pi r
Area = pi r * r

*/

Static
#include<stdio.h>
#include<conio.h>
void main()
{
    clrscr();
    float pi = 3.14,dia,cir,area;
    int r = 10;
    dia = 2 * r;
    cir = 2 * pi * r;
    area = pi * r * r;
    printf("\nThe area of circle :- %f",area);
    printf("\nThe diameter of a circle :- %f",dia);
    printf("\nThe circumference of a circle :- %f",cir);
getch();

}

 

 Output :- 

Dynamic 

#include<stdio.h>
#include<conio.h>
void main()
{
    clrscr();
    float pi = 3.14,dia,cir,area;
    int r;

    printf("Enter the radius :- ");

    scanf("%d",&r);
    dia = 2 * r;
    cir = 2 * pi * r;
    area = pi * r * r;
    printf("\nThe area of circle :- %f",area);
    printf("\nThe diameter of a circle :- %f",dia);
    printf("\nThe circumference of a circle :- %f",cir);
getch();