Thread: Floating Point: Stack Underflow

Code:

#include <iostream.h> 	//cout statement//
#include <conio.h>     	//getch() and clrscr()//
#include <string.h>		//strcpy()//
#include <time.h>			//time function//
#include <iomanip.h>		//decimal formatting//


								//function//
double mycalc(double x, double& y)
{

   y = (-2)*x*x + 3*x + 1;


}

           					//main part of program//
int main(void)
{
	double start,end,yvalue;
	time_t t=time(NULL);	//time function//

								//Fowler Statement//
	cout << setiosflags(ios::right);
	cout << setw(79) << ctime(&t)<<endl;
	cout << setw(79) << "Gavinn Niroopan"<<endl;
	cout << setw(79) << "Mr. Slack"<<endl;
	cout << setw(79) << "ICS 3MO-A"<<endl;
	gotoxy(28,9);
	cout << "Functions and Relations"<<endl;
	gotoxy(28,10);
	cout << "~~~~~~~~~~~~~~~~~~~~~~~"<<endl;
	cout << "Explanation: " <<endl;
	cout << "\tUsing variables and looping structures display a chart,the"<<endl;
	cout << "\tfollowing assignment will demonstrate a program structure, code"<<endl;
	cout << "\tlayout and use logic structures. The program will use data derived"<<endl;
	cout << "\tfrom a user and date acquired from the system at time of execution."<<endl;

	getch();         		//pause screen//
   clrscr();				//clear screen//

   cout << ctime(&t) << endl;

   gotoxy(28,3);
	cout << "Functions and Relations"<<endl;
	gotoxy(28,4);
	cout << "~~~~~~~~~~~~~~~~~~~~~~~"<<endl<<endl;
   cout << "What is the beginning reference in the range of  (-.2.5 to 3.5) - ";
   cin >>start;
   cout << "What is the ending reference in the range of  (-.2.5 to 3.5) - ";
   cin >> end;

   clrscr();

   cout << ctime(&t) << endl;

   gotoxy(28,3);
	cout << "Functions and Relations"<<endl;
	gotoxy(28,4);
	cout << "~~~~~~~~~~~~~~~~~~~~~~~"<<endl<<endl;
	cout << endl;
   cout <<setw(30)<< " Value of x " << setw(30) << " y = -2x^2 + 3x + 1 " << endl;
   cout <<setw(30)<< " ~~~~~~~~~~ " << setw(30) << " ~~~~~~~~~~~~~~~~~~ " << endl<<endl;

   for(start; start<=end; start = start + 0.5)

   {
   	mycalc(start,yvalue);

      cout << setiosflags(ios::fixed|ios:: right);
      cout << setprecision(1);
      cout << setw(26)<< start << setw(26) <<yvalue<<endl;

   }

   cout << endl;
   cout <<setw(45)<< "-Thank You-" << endl;



   getch();



}

I have a problem with the above code. There is a stack underflow error when i input -2.5 to 3.5. Could i get some help please. Thanks