C :

#include<stdio.h>
int main(){
int year;
  for(year=1900;year<=2000;year++){
    if(year%400==0 || year%4==0 && year%100!=0)
      printf("%d\n",year);
  }
  return 0;
}

C++ :

#include <stdio.h>
int main() {
	int year;
	for (year = 1900;year <= 2000;year++){
		if (year % 4 == 0) {
			if (year % 100 == 0) {
				if (year % 400 == 0) {
					printf("%d\n", year);
				}
			} else {
				printf("%d\n", year);
			}
		}
	}
	return 0;
}

Pascal :

var
  i,j:longint; 
begin
  for j:=1900 to 2000 do
    if (j mod 4=0) and (j mod 100<>0) or (j mod 400=0) then writeln(j);
end.

Java :

import java.util.*;
public class Main {
	public static void main(String args[]) {
		for(int year = 1900;year<=2000;year++){
			if((year%4==0&&year%100!=0)||year%400==0)
				System.out.println(year);
		}
	}
}

Python :

def isleap(n):
  if n%400==0 or (n%4==0 and n%100):
    return True
  else:
    return False
for i in xrange(1900,2001):
  if isleap(i):
    print i