Bilangan Prima

procedure TForm1.Button2Click(Sender: TObject);
var i,j:integer;
habisdibagi,isprime :boolean;
begin
ListBox1.Clear;

for i:=1 to 100 do
begin
if i <2 then isprime := False
else if i=2 then isprime := true
else if i mod 2 = 0 then isprime := false
else
begin
habisdibagi := false;
j:=3;
while (j <= Trunc(sqrt(i))+1) and (not habisdibagi) do
begin

if (i mod j) = 0 then habisdibagi := true;
j := j+2;
end;
if not habisdibagi then isprime := true;
end ;
if isprime then ListBox1.Items.Add(IntToStr(i));
end;
end;