Procedure OpenFile(nomer: byte);
begin
case Nomer of
1: begin assignfile(f1,'f1.dat');
    if FileExists('f1.dat') then reset(f1)
     else rewrite(f1); end;
2: begin assignfile(f2,'f2.dat');
    if FileExists('f2.dat') then reset(f2)
     else rewrite(f2); end;
3: begin assignfile(f3,'f3.dat');
    if FileExists('f3.dat') then reset(f3)
     else rewrite(f3); end;
end;
end;

Procedure OpenFile(a: ff);
begin
 case a of
  f1: str:='f1.dat';
  f2: str:='f2.dat';
  f3: str:='f3.dat';
 end;
 assignfile(a,str);
    if FileExists(str) then reset(a)
     else rewrite(a);
end;