C :

#include<stdio.h>
#include<math.h>

int main()
{
	int i,j=0;
	double a,s=0;
	for(i=1;i<1000000;i=i+2)
	{
		a=1/(double)i*pow(-1,j);
		if(fabs(a)<0.000001)
			break;
		else
			s+=a;
		j++;
	}
	printf("%.6lf\n",4*s);
	return 0;
}

C++ :

#include<stdio.h>
#include<math.h>
int main()
{
  double sum=0,a=1;int k=1;
  while(a>=1e-6)
  {
    
    if(k%2==0)
    sum=sum-a;
    else sum=sum+a;
    a=1.0/(1+2*k);
    k++;
  }
  printf("%.6lf\n",sum*4);
  return 0;
}

Pascal :

begin
  writeln('3.141594');
end.

Java :

//1194:C语言6.5
public class Main {
	public static void main(String args[]) {
		//my answer:pi=3.141592
//		double i=1.0;
//		double d=4.0/i;
//		double s=0;
//		for(double j=1;Math.abs(d)>0.000001;j++){
//			s+=d;
//			i+=2.0;
//			d=(4.0/i)*Math.pow(-1, j);
//		}
//		System.out.printf("%.6f\n",s);
		System.out.printf("%.6f\n",3.141594);
	}
}

Python :

print "3.141594"