The Sieve of Eratosthenes in Delphi Pascal 5

[SchreiberKugel]

Hello,

First of all, I am not an native English speaker so I apologize if there are any mistakes.

I am very new to programming, especially in Delphi Pascal. Now I have to do the Sieve of Eratosthenes as school-homework. I am in the process of learning the basics so please forgive me, if I´m just struggling with a simple problem.

The code I wrote is able to list all prim numbers from 2 to 200, but how do I change it to being able to list all prim numbers of the number I type into the edit? Also is there a way to make a text show up, if there is an error?

Help would be very appreciated.

type
  TForm1 = class(TForm)
    Berechnen: TButton;
    Label1: TLabel;
    Edit1: TEdit;
    Label2: TLabel;
    Memo1: TMemo;
    procedure BerechnenClick(Sender: TObject);
  private
    { Private-Deklarationen }
  public
    { Public-Deklarationen }
  end;
 
var
  Form1: TForm1;
 
implementation
 
{$R *.DFM}
 
 
 
 
procedure TForm1.BerechnenClick(Sender: TObject);
const
n = 200;
var
   zahl : array [2..n] of boolean;
   p,i,v : integer;
   weiter : boolean;
begin
   for i := 2 to n do zahl[i] := true;
   p := 2;
   while p <= n do
   begin
        v := 2*p;
        while v <= n do
        begin
             zahl[v] := false;
             v := v+p;
        end;
        p := p+1;
        if p <= n then weiter := true;
        while weiter do
         if (p<=n) and (zahl[p] = false)
         then
           p := p+1
         else
           weiter := false;
           end;
        for i := 2 to n do
        if zahl[i] then
        memo1.Lines.Add(IntToStr(i))
           end;
 
 
end.