{//////////////////////////////////////////////////////////
// Name: Peter M. Maurer
// Program: Sieve of Eratosthenes
// Due: Never
// Language: Pascal
//////////////////////////////////////////////////////////}

Program SieveE;
var Candidates : Array[0..999] of Integer;
    i,j : Integer;
begin
	{ define the sieve data structure    }
	for i := 0 to 999 do
	begin
		{ everything is potentially prime until proven otherwise }
		Candidates[i] := 1;
	end;
	{ Neither 1 nor 0 is prime, so flag them off  }
	Candidates[0] := 0;
	Candidates[1] := 0;
	{ start the sieve with the integer 0           }
	i := 0;
	while i<1000 do
	begin
		{ advance to the next un-crossed out number. }
		{ this number must be a prime                }
		while (i<1000) and (Candidates[i] = 0) do
		begin
			i := i+1;
                end;
		{ insure against running off the end of the data structure }
		if i<1000 then
		begin
			{ cross out all multiples of the prime, starting with 2*p. }
			j := 2;
                        while j*i < 1000 do
			begin
				Candidates[j*i] := 0;
				j := j+1;
                        end;
			{ advance to the next candidate }
			i := i+1;
		end
	end;
	{ all uncrossed-out numbers are prime (and only those numbers) }
	{ print all primes }
	for i := 0 to 999 do
	begin
		if Candidates[i] <> 0 then
		begin
                  writeln(i,' is prime');
		end
	end
end.