Вычисление площади фигуры1 / LABA0

#include<iostream.h>;//Stream library
#include<math.h>//Math library
#include<values.h>//Values library
#include<conio.h>//Screen library

float sq(float r0)
{
    float square;
    square = M_PI_2*r0*r0-4*r0*r0/5;
    return square;
}

int check(float r0)
{
    if ((r0<0) || (r0>100))
    {
      cout << "Radius incorrect";
      return 0;
    }
    return 1;

}


void main(void)//Main function that calculates area
{
    float       r       = 0; //Radius of circle that domain depends on


    /*Begin of greeting*/
    clrscr();
    cout << "\n";
    cout <<
    "Welcome.\n"
	 <<
    "This is programm that calculates domain area, that depends on radius (R).\n";

    /*End of greeting*/

    /*Begin of requirement*/
    do
    {

      do
      {
	cout << "\nPlease insert radius of circle [0," << "100" << "]:\n" << "r=";
	cin >> r;
      }
      while ((!check(r)));
    cout << "Nessesary area is: " << sq(r); //Result printing
    cout << "\n\nThank you for using our programm.\n"   //
    << "All rights reserved. (c)\n";//Parting
    cout << "\n" << "For exit press Esc. ";
    }
    while(getch()!=27);
    /*End of requirement*/


    //getch();
}