C :

#include<stdio.h>
int main()
{
	int i;
	double s=0,a;
	for(i=1;i<=100;i++)
	{
		a=0;
		a=1.0/i;
		s=s+a;
	}
	printf("%.3lf",s);	
	return 0; 
}

C++ :

#include<iostream>
#include<cstdio>
using namespace std;
int main()
{
  float a=0;
  for(int i=1;i<=100;++i)
   a=a+1.0/i;
  printf("%0.3lf\n",a);
  return 0;
}

Pascal :

program aa;
var a,d,e,max,min:longint;
b,c:real;
begin
 b:=0;
 c:=0;
 for a:=1 to 100 do
 begin
  b:=1/a;
  c:=c+b;
 end;
 write(c:0:3);
end.