Automate pascal program command line input

Program SPMake;
var
  f : text;
  w : text;
  In_file : String[12];
  In_pref : String[8];
  out_file : String[12];
  lines   : longint;
  suffix  : String[3];
  Alldone : Boolean;
  file_no : integer;
  c : char;
  asc : longint;
 
begin
  Write('Name of SPOOL files -> ');
  Readln(In_file);
  if (length(In_file)=0) or (pos('.',In_file)>0) then
  begin
    writeln('Invalid SPOOL file name.');
    halt;
  end;
 
  Write('File to be created -> ');
  Readln(Out_file);
 
  if (length(Out_file)=0) or (pos('.',Out_file)>9)
  or ((pos('.',In_file)=0) and (length(In_file)>8)) 
  or (length(Out_file)>12)   then
  begin
    writeln('Invalid output file name.');
    halt;
  end;
  In_Pref:=In_file;
 
  Assign(w, out_file);
  Rewrite(w);
    
 
 
  Alldone := False;
 
  file_no:=0;
  while not alldone do 
  Begin
    file_no:=file_no+1;
    str(file_no,suffix);
    while length(suffix)<3 do suffix:='0'+suffix;
 
    In_file:=In_pref+'.'+suffix;  
    Assign(f, In_file);
    {$I-}
    Reset(f);
    {$I+}
    If IOResult<>0 then
    begin
      Alldone:=True;
      if suffix='001' then 
      begin
        write('File ',in_file,' not found.');
        halt;
      end;
    end else
    begin  
      lines:=0;
      writeln('Reading ', In_file, ' into ',out_file);
      while not eof(f)  do
      begin
        read(f,c);
        asc:=ord(c);
        if (asc>9) and (asc<>29) then write(w,c);
 
        {if (asc>= 13) and (asc <= 126) then write(w,c);}
      end;
      close(f);
      erase(f);
    end;
  end;    
  Close(w);
  Writeln('Files combined.');
end.