procedure TForm1.Button1Click(Sender: TObject);

var
MyTextFile: TextFile;
S: String;
i: integer;

begin
AssignFile(MyTextFile, 'MyTextFile.txt');
Rewrite(MyTextFile);

try
for i := 1 to 5 do
begin
S := 'This is line # ';
Writeln(MyTextFile, S, i);
end;
finally
CloseFile(MyTextFile);
end;
end;
