C :

#include <stdio.h>
#include <stdlib.h>

/* run this program using the console pauser or add your own getch, system("pause") or input loop */
void fun(x)
{
    //int x;
	double y;
	y=x*x-3.14*x-6;
	printf(" %d\t%.2f",x,y);	
}
int main(int argc, char *argv[]) {
	int x;
	printf("  x\ty\n");
	for(x=-10;x<10;x++)
	{
		fun(x);
		printf("\n");
	}
	fun(x);
	return 0;
}

C++ :

#include <iostream>
#include<iomanip>

using namespace std;

double fun(int x);
int main()
{

cout<<"  x\ty"<<endl;
for(int i=-10;i<=10;i++)
{
cout<<" "<<i<<"\t"<<fixed<<setprecision(2)<<fun(i)<<endl;
}

return 0;
}

double fun(int x)
{
double y=(double)x*(double)x-3.14*(double)x-6;
return y;
}