C Program to Find Area of a Circle

 C program to find the area of a circle

The formula of the Area of a circle is 

π

r

2

but some time diameter is given in this time we have to divide the diameter of a circle by 2 to get the radius.

r is a Radius and Radius is a  length from the center to the edge of a circle  

π is pi and it is a mathematic symbol whose value is 22/7 or 3.14

In this article area of the circle is calculated as below

1. C program to find the area of a circle (When the value of π is 3.14)

2. C program to find the area of a circle (When the value of π is 22/7)

3. C program to find the area of a circle using the diameter

4. C program to find the area of a circle using the function 

5. C program to find the area of a circle using #define function 

Note

This is a comment written inside //. It does not have to be written while programming. The reason for using it is for the convenience and understanding of another programmer

C program to find the area of a circle using radius (When the value of π is 3.14)

Program 

#include<stdio.h> #include<conio.h> void main() {    // Value of radius is stored in r variable    float A, r;    // taking input of radius from users    printf("\n Enter radius of a circle");    scanf("%f", &r);    // using formula of circle π                A=(22*r*r)/7;    // printing Area of circle    printf("\n Area of circle = %f", A);    getch(); }

Output

 C program to find the area of a circle (When the value of π is 22/7)

We can use the value of π 22/7 instead of 3.14 but the answer comes slightly different and the program to find the area of a circle using the value of π is 22/7

Program 

#include<stdio.h> #include<conio.h>  void main()  {           // Value of radius stored is in r variable           float A, r;           // taking input of radius from user           printf("\n Enter radius of a circle");           scanf("%f", &r);  //using formula of circle pi * radius * radius value of pi is 22/7           A=(22*r*r)/7;           // printing area of a circle          printf("\n Area of circle = %f", A);          getch();  }

Output

C program to find the area of a circle using a diameter

The diameter of a circle is the length of the circle from one edge to another edge, where the radius is a length of circle central to one edge of the circle.

So,

Radius = Diameter/2

Program 

#include<stdio.h> #include<conio.h> void main() {     float d, r, A;     // taking input of diameter from user     printf("\n Enter a diameter of a circle");     scanf("%f",&d);     // converting diameter into radius     r=d/2;     //using formula of circle p * radius * radius value of p is 22/7     A=3.14*r*r;     printf("\n Area of a circle is %f", A);     getch(); }

Output

C program to find the Area of circle using function

#include<stdio.h> #include<conio.h> void area(float); // function prototype void main() {    float r;    // taking input of radius from users    printf("\n Enter a radius of a circle");    scanf("%f", &r);    area(r); // function call    getch(); } void area(float r) {    float A;   //using formula of circle p * radius * radius value of p is 22/7    A=3.14*r*r;    // Printing area of circle    printf("\n Area of a circle is %f", A);    getch();    }

Output

C program to find the area of a circle using a #define function 

#define is used defines a macro substitution and symbolic contact  

 

Program 

#include<stdio.h> #include<conio.h> #define pi 3.14 void main() {     float r, A;     // taking input of diameter from user     printf("\n Enter a radius of a circle");     scanf("%f",&r);     /* Using area of circle area = r*r and pi is a    variable define under #define function */     A=pi*r*r;     // Printing Area of circe     printf("\n Area of a circle is %f", A);     getch(); }

Output 

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