DEFINITION MODULE Files;
(* Sequential files over the runtime shim (stdio). File is an opaque
   handle (a pointer-sized value); NIL means the open failed.
   Text is written/read as descriptor strings; integers as decimal. *)

TYPE FileRec;
TYPE File = POINTER TO FileRec;

PROCEDURE OpenRead(VAR name : ARRAY OF CHAR) : File;
PROCEDURE OpenWrite(VAR name : ARRAY OF CHAR) : File;
PROCEDURE Close(f : File);

PROCEDURE ReadChar(f : File) : CHAR;
PROCEDURE ReadInt(f : File) : INTEGER;
PROCEDURE WriteChar(f : File; c : CHAR);
PROCEDURE WriteInt(f : File; n : INTEGER);
PROCEDURE WriteString(f : File; VAR s : ARRAY OF CHAR);
PROCEDURE WriteLn(f : File);

END Files.