../code/conceptPage.scroll

id modula-2
name Modula-2
appeared 1978
creators Niklaus Wirth
tags pl
blog https://freepages.modula2.org/oldnew.html
download https://www.modula2.org/adwm2/download.php
lab ETH Zurich
fileExtensions mod m2 def MOD DEF mi md

gdbSupport true
fileType text
docs https://www.modula2.org/tutor/introduction.php
rosettaCode http://www.rosettacode.org/wiki/Category:Modula-2
country Switzerland

helloWorldCollection Modula-2
 (* Hello World in Modula-2 *)
 
 MODULE HelloWorld;
 FROM InOut IMPORT WriteString,WriteLn;
 BEGIN
   WriteString("Hello World!");
   WriteLn;
 END HelloWorld.
 
pygmentsHighlighter Modula-2
 filename modula2.py
 fileExtensions def mod
leachim6 Modula 2
 filepath m/Modula 2.mod
 example
  MODULE HelloWorld;
  
  FROM Terminal2 IMPORT WriteString, WriteLn;
  
  BEGIN
  
      WriteString("Hello World");
      WriteLn;
      
  END HelloWorld.

multiLineCommentTokens (* *)
printToken WriteString
stringToken "
booleanTokens TRUE FALSE

hasComments true
hasLineComments false
hasPointers true
hasSinglePassParser true
hasOperatorOverloading false
hasMultiLineComments true
 (* A comment
 *)
hasPrintDebugging true
hasSemanticIndentation false
hasCaseInsensitiveIdentifiers false
hasStrings true
 "Hello world"
hasBooleans true

wikipedia https://en.wikipedia.org/wiki/Modula-2
 example
  ABS         EXCL            LONGINT    REAL
  BITSET      FALSE           LONGREAL   SIZE
  BOOLEAN     FLOAT           MAX        TRUE
  CAP         HALT            MIN        TRUNC
  CARDINAL    HIGH            NIL        VAL
  CHAR        INC             ODD
  CHR         INCL            ORD
  DEC         INTEGER         PROC
 related modula mesa pascal modula-3 oberon ada lua seed7 zonnon isbn
 summary Modula-2 is a computer programming language designed and developed between 1977 and 1985 by Niklaus Wirth at the Swiss Federal Institute of Technology in Zurich (ETH Zurich) as a revision of Pascal to serve as the sole programming language for the operating system and application software for the personal workstation Lilith. The principal concepts were: The module as a compilation unit for separate compilation The coroutine as the basic building block for concurrent processes Types and procedures that allow access to machine-specific data. Modula-2 was viewed by Niklaus Wirth as a successor to his earlier programming languages Pascal and Modula. The language design was also influenced by the Mesa language and the new programming possibilities of the early personal computer Xerox Alto, both from Xerox, that Wirth saw during his 1976 sabbatical year at Xerox PARC. The computer magazine BYTE devoted the August 1984 issue to the language and its surrounding environment.
 pageId 24102707
 dailyPageViews 87
 created 2002
 backlinksCount 211
 revisionCount 508
 appeared 1978
 fileExtensions mod m2 def MOD DEF mi md

hopl https://hopl.info/showlanguage.prx?exp=817
tiobe Modula-2

githubBigQuery Modula-2
 repos 115
 users 103

linguistGrammarRepo https://github.com/harogaston/Sublime-Modula-2
 firstCommit 2014
 lastCommit 2015
 committerCount 4
 commitCount 27
 sampleCount 1
 example
  IMPLEMENTATION MODULE HuffChan;
  
  (*
   This module shows how to redefine standard IO file functions. It provides
   functions for reading and writing packed files opened in Raw mode.
  *)
  
  IMPORT IOChan, IOLink, ChanConsts, IOConsts, SYSTEM, Strings;
  FROM Storage IMPORT ALLOCATE, DEALLOCATE;
  
  CONST
    rbldFrq = 512;	(* means: every 512 bytes rebuild table *)
  
  TYPE
    charTap  = POINTER TO ARRAY [0..MAX(INTEGER)-1] OF CHAR;
    smbTp = POINTER TO smbT;
  
    smbT = RECORD			(* Huffman's tree *)
      ch			: CHAR;
      n			: CARDINAL; (* frequncy of char ch *)
      left,right,next	: smbTp;
    END;
  
    tblT = RECORD		(* bit sequence for code *)
      vl		: CARDINAL;	(* bit sequence *)
      cnt		: INTEGER;	(* it length *)
    END;
  
    lclDataT = RECORD	(* channel's local data *)
      tRoot 	: smbTp;
      htbl	: ARRAY [0..255] OF tblT;     (* code -> bit sequence table *)
      ftbl  	: ARRAY [0..255] OF CARDINAL; (* frequncey table *)
      wBf,rb1,rb2	: CARDINAL;
      wbc,rbc,smc	: INTEGER;
      chid	: IOChan.ChanId;
    END;
    lclDataTp = POINTER TO lclDataT;
    charp     = POINTER TO CHAR;
  
  VAR
    did	: IOLink.DeviceId;
    ldt	: lclDataTp;
  
  
  PROCEDURE Shf(a:CARDINAL; b : INTEGER) : CARDINAL; (* shl a,b (or shr) *)
  BEGIN
    RETURN SYSTEM.CAST(CARDINAL,SYSTEM.SHIFT(SYSTEM.CAST(BITSET,a),b));
  END Shf;
  
  PROCEDURE wrDword(a:CARDINAL);	(* write 4 bytes to file *)
  BEGIN
    IOChan.RawWrite(ldt^.chid,SYSTEM.ADR(a),4);
  END wrDword;
  
  PROCEDURE rdDword() : CARDINAL;  (* read 4 bytes from file *)
  VAR
    a,z : CARDINAL;
  BEGIN
    a:=0;
    IOChan.RawRead(ldt^.chid,SYSTEM.ADR(a),4,z);
    RETURN a;
  END rdDword;
  
  PROCEDURE wrSmb(ch : CHAR);	(* write bit sequence for code ch *)
  VAR
    v,h : CARDINAL;
    b,c : INTEGER;
  BEGIN
    WITH ldt^ DO
      v:=htbl[ORD(ch)].vl;
      c:=htbl[ORD(ch)].cnt;
      IF c+wbc<=32 THEN
        wBf:=Shf(wBf,c);
        wBf:=wBf+v;
        wbc:=wbc+c;
        IF wbc=32 THEN
  	wrDword(wBf);
  	wBf:=0; wbc:=0;
        END;
        RETURN;
      END;
      b:=c+wbc-32;
      h:=Shf(v,-b);
      wBf:=Shf(wBf,32-wbc)+h;
      wrDword(wBf);
      wBf:=v-Shf(h,b);
      wbc:=b;
    END;
  END wrSmb;
  
  PROCEDURE flush();	(* write data in buffer *)
  BEGIN
    WITH ldt^ DO
      wBf:=Shf(wBf,32-wbc);
      wrDword(wBf);
    END;
  END flush;
  
  PROCEDURE getSym() : CHAR; (* find code for first bit sequence in buffer *)
  VAR
    t,i : CARDINAL;
    b   : INTEGER;
  BEGIN
    WITH ldt^ DO
      IF rbc<=32 THEN
        rb2:=rdDword();
        t:=Shf(rb2,-rbc);
        IF rbc=32 THEN t:=0; END;
        rb1:=rb1+t;
        rb2:=Shf(rb2,32-rbc);
        IF rbc=0 THEN rb2:=0; END;
        rbc:=rbc+32;
      END;
      FOR i:=0 TO 255 DO
        t:=Shf(rb1,htbl[i].cnt-32);
        IF t=htbl[i].vl THEN
  	rb1:=Shf(rb1,htbl[i].cnt);
  	b:=32-htbl[i].cnt;
  	t:=Shf(rb2,-b);
  	rb1:=rb1+t;
  	rb2:=Shf(rb2,32-b);
  	rbc:=rbc+b-32;
  	RETURN CHR(i);
        END;
      END;
    END;
  END getSym;
  
  PROCEDURE Insert(s : smbTp); (* insert new character in Huffman's tree *)
  VAR
    cr : smbTp;
  BEGIN
    WITH ldt^ DO
      IF tRoot=NIL THEN
        cr:=tRoot;
        tRoot:=s;
        s^.next:=cr;
        RETURN;
      ELSIF tRoot^.n<=s^.n THEN
        cr:=tRoot;
        tRoot:=s;
        s^.next:=cr;
        RETURN;
      END;
      cr:=tRoot;
      WHILE (cr^.next<>NIL) & (cr^.next^.n>s^.n) DO
        cr:=cr^.next;
      END;
      s^.next:=cr^.next;
      cr^.next:=s;
    END;
  END Insert;
  
  PROCEDURE BuildTree(); (* build Huffman's tree *)
  VAR
    cr,ocr,ncr : smbTp;
  BEGIN
    WITH ldt^ DO
      LOOP
        ocr:=NIL; cr:=tRoot;
        WHILE cr^.next^.next<>NIL  DO
  	ocr:=cr; cr:=cr^.next;
        END;
        NEW(ncr);
        ncr^.n:=cr^.n+cr^.next^.n;
        ncr^.left:=cr;
        ncr^.right:=cr^.next;
        IF ocr<>NIL THEN
  	ocr^.next:=NIL;
  	Insert(ncr);
        ELSE
  	tRoot:=NIL;
  	Insert(ncr);
  	EXIT;
        END;
      END;
    END;
  END BuildTree;
  
  PROCEDURE BuildTable(cr: smbTp; vl,n: CARDINAL); (* build table: code -> bit sequence *)
  BEGIN
    WITH ldt^ DO
      IF cr^.left=NIL THEN
        htbl[ORD(cr^.ch)].vl:=vl;
        htbl[ORD(cr^.ch)].cnt:=n;
        DISPOSE(cr);
        RETURN;
      END;
      vl:=vl*2;
      BuildTable(cr^.left,vl,n+1);
      BuildTable(cr^.right,vl+1,n+1);
      DISPOSE(cr);
    END;
  END BuildTable;
  
  PROCEDURE clcTab(); (* build code/bitseq. table from frequency table *)
  VAR
    i : CARDINAL;
    s : smbTp;
  BEGIN
    WITH ldt^ DO
      tRoot:=NIL;
      FOR i:=0 TO 255 DO
        NEW(s);
        s^.ch:=CHR(i);
        s^.n:=ftbl[i];
        s^.left:=NIL; s^.right:=NIL; s^.next:=NIL;
        Insert(s);
      END;
      BuildTree();
      BuildTable(tRoot,0,0);
    END;
  END clcTab;
  
  PROCEDURE iniHuf();
  VAR
    i : CARDINAL;
  BEGIN
    WITH ldt^ DO
      FOR i:=0 TO 255 DO
        ftbl[i]:=1;
      END;
      wBf:=0; wbc:=0; rb1:=0; rb2:=0; rbc:=0;
      smc:=0;
      clcTab();
    END;
  END iniHuf;
  
  
  PROCEDURE RawWrite(x: IOLink.DeviceTablePtr; buf: SYSTEM.ADDRESS;
  		len: CARDINAL);
  VAR
    i	: CARDINAL;
    ch	: CHAR;
    cht	: charTap;
  BEGIN
    IF len = 0 THEN RETURN; END;
    ldt:=SYSTEM.CAST(lclDataTp,x^.cd);
    cht:=SYSTEM.CAST(charTap,buf);
    WITH ldt^ DO
      FOR i:=0 TO len-1 DO
        ch:=cht^[i];
        wrSmb(ch);
        IF ch = 377C THEN wrSmb(ch); END;
        ftbl[ORD(ch)]:=ftbl[ORD(ch)]+1; smc:=smc+1;
        IF smc=rbldFrq THEN
  	clcTab();
  	smc:=0;
        END;
      END;
    END;
    x^.result:=IOChan.ReadResult(ldt^.chid);
  END RawWrite;
  
  PROCEDURE RawRead(x: IOLink.DeviceTablePtr; buf: SYSTEM.ADDRESS;
  		blen: CARDINAL; VAR len: CARDINAL);
  VAR
    i	: CARDINAL;
    cht	: charTap;
    ch	: CHAR;
  BEGIN
    ldt:=SYSTEM.CAST(lclDataTp,x^.cd);
    cht:=SYSTEM.CAST(charTap,buf);
    IF (blen=0) OR (x^.result<>IOConsts.allRight) THEN len:=0; RETURN; END;
    WITH ldt^ DO
      FOR i:=0 TO blen-1 DO
        ch:=getSym();
        IF ch = 377C THEN
  	ch:=getSym();
  	IF ch = 0C THEN
  	  x^.result:=IOConsts.endOfInput;
  	  len:=i; cht^[i]:=0C;
  	  RETURN;
  	END;
        END;
        cht^[i]:=ch;
        ftbl[ORD(ch)]:=ftbl[ORD(ch)]+1; smc:=smc+1;
        IF smc=rbldFrq THEN
  	clcTab();
  	smc:=0;
        END;
      END;
      len:=blen;
    END;
  END RawRead;
  
  PROCEDURE CreateAlias(VAR cid: ChanId; io: ChanId; VAR res: OpenResults);
  VAR
    x	: IOLink.DeviceTablePtr;
  BEGIN
    IOLink.MakeChan(did,cid);
    IF cid = IOChan.InvalidChan() THEN
      res:=ChanConsts.outOfChans
    ELSE
      NEW(ldt);
      IF ldt=NIL THEN
        IOLink.UnMakeChan(did,cid);
        res:=ChanConsts.outOfChans;
        RETURN;
      END;
      x:=IOLink.DeviceTablePtrValue(cid,did,IOChan.notAvailable,"");
      ldt^.chid:=io;
      x^.cd:=ldt;
      x^.doRawWrite:=RawWrite;
      x^.doRawRead:=RawRead;
      res:=ChanConsts.opened;
      iniHuf();
      x^.result:=IOConsts.allRight;
    END;
  END CreateAlias;
  
  PROCEDURE DeleteAlias(VAR cid: ChanId);
  VAR
    x	: IOLink.DeviceTablePtr;
  BEGIN
    x:=IOLink.DeviceTablePtrValue(cid,did,IOChan.notAvailable,"");
    ldt:=x^.cd;
    IF ldt^.rbc=0 THEN
      wrSmb(377C);
      wrSmb(0C);
      flush();
    END;
    DISPOSE(ldt);
    IOLink.UnMakeChan(did,cid);
  END DeleteAlias;
  
  BEGIN
    IOLink.AllocateDeviceId(did);
  END HuffChan.
  

isbndb 1
 year|publisher|title|authors|isbn13
 1985|Springer-Verlag|Programming in Modula-2 (Texts and monographs in computer science)|Wirth, Niklaus|9780387150789

githubLanguage Modula-2
 fileExtensions mod
 trendingProjectsCount 0
 type programming
 aceMode text
 tmScope source.modula2
 repos 306

indeedJobs modula-2 developer
 2022 0

semanticScholar 0