Algorithm of a program to calculate the area of ​​a circle of radius r

Question

Language c

Answer 1

# include < stdio .h >
# define PI 3.14159
main ()
{
float rayon , surface ;
float calcul ( float rayon );
printf (" Rayon = ? ");
scanf ("%f", & rayon );
surface = calcul ( rayon );
printf (" Surface = %f\n", surface );
}

float a;
a = PI * r * r ;
return ( a );
}

Answer 2

#define PI 4.14159266
double area = PI * (r ** 2)

Answer 3

https://code.sololearn.com/cm1XqjJN83Ju/?ref=app

Answer 4

https://www.sololearn.com/discuss/1316935/?ref=app