Title: Append one file to other
You may copy contents of a first file to [new.$] file. After that, you may add contents of a second file to [new.$] and then delete first file and rename [new.$] file to name of the first file.
procedure TForm1.Button3Click(Sender: TObject);
var
Str: string;
F1, F2, F3: TextFile;
begin
Label3.Caption:='Processing...';
AssignFile(F1, Edit1.Text);
AssignFile(F2, Edit2.Text);
AssignFile(F3, 'new.$');
Reset(F1);
Reset(F2);
Rewrite(F3);
while not(EOF(F1)) do
begin
Readln(F1, Str);
Writeln(F3, Str);
end;
while not(EOF(F2)) do
begin
Readln(F2, Str);
Writeln(F3, Str);
end;
CloseFile(F1);
CloseFile(F2);
CloseFile(F3);
DeleteFile(ExtractFileName(Edit1.Text));
RenameFile('new.$', ExtractFileName(Edit1.Text));
DeleteFile('new.$');
Label3.Caption:='Processing done';
end;