How to find volume of cylinder using function and without arguments?

CODE

How to find volume of cylinder using function and without arguments?

// Write a program to find volume of cylinder using function and without arguments..

int main()

{

    void vol();                    //function declaration

    vol();                         //function calling

}

void vol()                        //function defination

{

    float h,r,v;

    printf("\n enter radius and height:");

    scanf("%f%f",&r,&h);

    v=3.14*r*r*h;

    printf("\n volume of cylinder=%f",v);

}

Output:

enter radius and height:

5

7

 volume of cylinder=549.500000