We will read strings from each file while each of files has a data. And we will compare each string from the first file with corresponding string from the second file. All differences we will write in a memo.
procedure TForm1.Button1Click(Sender: TObject); var First, Second: TextFile; Str, Str2: string; begin Memo1.Clear; if (Edit1.Text<>'')and(Edit2.Text<>'') then begin AssignFile(First, Edit1.Text); AssignFile(Second, Edit2.Text); Reset(First); Reset(Second); while not EOF(First) do begin if EOF(Second)=True then begin Memo1.Lines.Add('*** ATTENTION ***'); Memo1.Lines.Add('SECOND file has finished but FIRST file has had a data yet.'); Break; end; Readln(First, Str); Readln(Second, Str2); if CompareStr(Str, Str2)<>0 then begin Memo1.Lines.Add('FIRST - '+Str); Memo1.Lines.Add('SECOND - '+Str2); Memo1.Lines.Add(' '); end; end; if EOF(Second)=False then begin Memo1.Lines.Add('*** ATTENTION ***'); Memo1.Lines.Add('FIRST file has finished but SECOND file has had a data yet.'); end; CloseFile(First); CloseFile(Second); if Memo1.Lines.Count=0 then Memo1.Lines.Add('FIRST file is identical to SECOND file'); end; end;