modula2.txt

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IMPLEMENTATION MODULE Ticker;

(* (C) Copyright 1987 Fitted Software Tools. All rights reserved.

    This module is part of the example multitasking communications program
    provided with the Fitted Software Tools' Modula-2 development system.

    Registered users may use this program as is, or they may modify it to
    suit their needs or as an exercise.

    If you develop interesting derivatives of this program and would like
    to share it with others, we encourage you to upload a copy to our BBS.
*)


FROM SYSTEM     IMPORT ASSEMBLER, ADDRESS;
FROM System     IMPORT TermProcedure, GetVector, SetVector, ResetVector;

(* $S- *)

VAR
    ClockTick       :ADDRESS;


PROCEDURE Tick;
(*
    Timer tick ISR

    This ISR could have been implemented as an IO process, but that
    would be boring!

    This serves as an example on how to write interrupt routines that
    are attached to the interrupt vectors with some help from System.
*)
BEGIN
    ASM
        STI
        PUSH    DS
        MOV     DS, CS:[0]
        INC     Ticks
        PUSHF                       (* Chain interrupt *)
        CALL    FAR ClockTick       (* Invoke the system's clock ISR *)
        POP     DS
        IRET
    END;
END Tick;


PROCEDURE StopClock;
BEGIN
    (* restore the original clock ISR *)
    ResetVector( 8, ClockTick );
END StopClock;


BEGIN
    Ticks := 0;
    GetVector( 8, ClockTick );      (* save system's clock ISR *)
    TermProcedure( StopClock );     (* set procedure to restore system's ISR *)
                                    (* on program termination *)
    SetVector( 8, Tick );           (* install our own clock ISR *)

END Ticker.

IMPLEMENTATION MODULE People;
  FROM Strings IMPORT CompareStr, Assign;

  CLASS Person;    (* a class implementation *)
    PROCEDURE isMale() :BOOLEAN;
      BEGIN
        RETURN sex = male;
      END isMale;
    INIT
      name := "";
      sex := unknown;
 END Person;

  CLASS Programmer;  (* a class implementation *)
    PROCEDURE isSmart() :BOOLEAN;
      BEGIN
        RETURN CompareStr(favoriteLanguage,"Modula-2") = 0;
      END isSmart;
    INIT
      favoriteLanguage := "?";
  END Programmer;

  CLASS Vendor;      (* a local class declaration *)
    INHERIT Programmer;
    BusinessAddress : ARRAY [0..40] OF CHAR;
    PROCEDURE GetAddress (VAR Address : ARRAY OF CHAR);
      BEGIN
        Assign(BusinessAddress, Address)
      END GetAddress;
    INIT
      BusinessAddress := "PO Box 867403, Plano, Texas"
  END Vendor;
END People.