[fpc-pascal]quick question

[r.w.h]

begin
if exists ('bot.log')
then begin
assign(ftb,'bot.log');
append(ftb);
writeln(ftb,'bot log created'); // find away to enter time , date
close(ftb);
end
else
begin
assign(ftb,'bot.log');
reset(ftb);
writeln(ftb,'the botlog was created');
close(ftb);
end;
end;

whats wrong with the code.
i get the following error on compile.
botlog.pp(25,4) Error: Identifier not found "exists"

Rob Harris