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Modula-2 is a pl created in 1978 by Niklaus Wirth.

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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. Read more on Wikipedia...

Example from hello-world:
MODULE HelloWorld; FROM Terminal2 IMPORT WriteString, WriteLn; BEGIN WriteString("Hello World"); WriteLn; END HelloWorld.
Example from the Hello World Collection:
(* Hello World in Modula-2 *) MODULE HelloWorld; FROM InOut IMPORT WriteString,WriteLn; BEGIN WriteString("Hello World!"); WriteLn; END HelloWorld.
Example from Linguist:
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.
Example from Wikipedia:

Language features

Feature Supported Example Token
"Hello world"
Print() Debugging WriteString
MultiLine Comments
(* A comment
(* *)
Semantic Indentation ϴ
Operator Overloading ϴ
Line Comments ϴ

Books about Modula-2 from ISBNdb

title authors year publisher
Programming in Modula-2 (Texts and monographs in computer science) Wirth, Niklaus 1985 Springer-Verlag
assembly-language.html · modula-2.html · dart.html

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