TweetFollow Us on Twitter

Modula-2 Compiler
Volume Number:1
Issue Number:6
Column Tag:Modula-2

Modula-2 Compiler by Modula Corporation

By Jörg Langowski

The ‘almost released’ beta version of the Modula-2 compiler by Modula Corporation has been around for some time now on several peoples’ desks, including mine. I feel it is time to report some of my experiences with this product.

Modula 2 is in some way the successor of Pascal, created by the same author, Niklaus Wirth from Zürich. Simple Modula 2 programs almost look like Pascal programs. Supposedly some of the inconveniences of Pascal have been straightened out in Modula 2, e.g., the rigid order in which declarations are made in Pascal has been relaxed. The most important new concept is that of modular compilation, which means that external (library) definitions can be ‘imported’ from separately compiled ‘modules’ at compile time and checked for correct passing of parameters, type mismatches etc

But I do not want to talk about language differences here. There has been a whole issue of BYTE dealing with Modula recently, and if you plan to use the Modula-2 compiler, you will have to get the standard reference book, ‘Programming in Modula-2’, by Niklaus Wirth, anyway.

The Modula-2 version that I received from Modula Corporation came on one Macintosh disk with a three-ring binder manual. The disk contains:

- The Modula-2 compiler and linker. Both are compiled Modula-2 programs, which means (for this system) that they are not native 68000 code, but rather M-code for a virtual machine, which has to be interpreted.

- The interpreter. The disk contains two versions, one of which is used to run the compiler and linker, the other one to run your compiled Modula-2 program.

- System libraries with precompiled modules for I/O, file handling, number conversion, string manipulation and - most important of all - toolbox access.

- a Decode utility to disassemble M-code. I found this of little use since I had no definition of the M-code instructions available.

- source code of a Graphics Demo and the Edit sample application that is also part of the IM manual.

- Edit, the same editor as in the Asm/Edit system.

- Rmaker, the (in)famous resource maker.

The manual gives a rather concise introduction on how to use the compiler and linker if you want to write a simple program or create a separately compiled module. Beside these instructions, it contains a listing of all the predefined modules that come with the system.

If you want to write a program that does just simple I/O and do not care about the user interface, you can use the standard GrafPort that the system comes up with when you start your application. Unfortunately, this is the full screen, not a nicely set up window like some other compilers have. You merely get a blank screen terminal emulation; if you want to use a window, you will have to define it through toolbox calls. You might want to take a look at the sample program in Listing 1 now.

This is a short matrix multiplication routine that initializes two matrices and determines the product matrix, then types out one element of the product as a check. You see that the actual calculation comprises about 25% of the total program, the rest is definitions and setting up of the window. Having read some of the other examples in MacTutor, you might not be surprised at that kind of overhead. The main parts of the program are:

- the IMPORT declarations, which get routines out of precompiled modules; note that not even simple I/O is defined by default, you have to import procedures for any kind of I/O that you want to do.

- some TYPE and VAR declarations - similar to Pascal. Integers (signed) and Cardinals (unsigned) are 16 bit by default. If you need a 32 bit integer, you have to use the LongCard TYPE, which is a record with the fields h and l, both CARDINAL. You have to assign them separately.

- toolbox PROCEDURE declarations. Unfortunately, there is no way to access a toolbox routine through its trap number directly; the routines are called (presumably) through numbers in another module, and the definitions that you have to use are given in the manual. Most of the toolbox routines (no - not all of them) are included. The definitions make as much sense to me as they make to you, but they seem to work.

- the actual program. You will notice there that the string format has to be converted from Modula (zero byte at the end) to Macintosh (character count in front) format.

The program is edited using the well-known Edit program, then passed as a file with the extension .MOD to the compiler. Compilation of this sample program takes 2 min 58 secs, add to that 25 secs to bring up the compiler. The reason for the system being so slow is of course that the compiler is written in M-code, too, and is interpreted. You quickly learn to examine your code very carefully for errors before you call up the compiler! One rather annoying feature of Modula-2 did not make things easier, either: Upper and lower case are distinguished, and it makes a difference whether you write WindowPtr or windowptr. Oh well Debugging the example, after it ‘almost’ ran, took me one hour, most of that time waiting for the compiler to finish.

The compiled program is then linked with the library modules (no linker errors here, since external references are already checked for completeness by the compiler) and you get a .LOD file, which, when double clicked, is executed by the Modula runtime interpreter.

Even though the compiler is slow, the generated code is rather fast. The example takes 21 seconds to execute. This is faster as you can ever do with the built-in 80-bit floating point package (judged from a similar program in Forth, which took over 40 seconds, most of that being floating point time). Modula-2 has its own 32-bit floating point package built in, which is precise enough for most applications. The Sieve runs 9 seconds per iteration, making a total of 90 secs for the standard 10 iterations. This, in turn, is slower than Forth (probably because the ratio M-code to built-in 68000 routines is higher in this case).

The timing results, in my opinion, make the Modula-2 system a very satisfactory choice for scientific and engineering applications. If Modula Corporation could come up with a compiler written in machine code, program development would be much more fun, too.

MODULE Matmul;

FROM InOut  IMPORT ReadCard, WriteCard, WriteString, WriteLn;
FROM Terminal  IMPORT ClearScreen;
FROM RealInOut   IMPORT ReadReal, GWriteReal;
FROM QuickDrawTypes  IMPORT Rect, GrafPtr, Str255, LongCard;
FROM ToolBoxTypes  IMPORT WindowPtr, WindowRecord;
FROM Strings   IMPORT StrModToMac;
FROM SYSTEM IMPORT ADDRESS;

CONST   CX = 355B;  QuickDrawModNum = 1; ToolBoxModNum = 2;

TYPE  Ptr = ADDRESS;

VAR   i,j,k : CARDINAL;
 sum,p,q : REAL;
 a : ARRAY [1..20] OF ARRAY [1..30] OF REAL;
 b : ARRAY [1..30] OF ARRAY [1..20] OF REAL;
 c : ARRAY [1..30] OF ARRAY [1..30] OF REAL;
 Wbounds : Rect;
 Wtitle : Str255;
 Wnew : WindowPtr;
 WrefCon, behind, OnHeap: LongCard;
 
PROCEDURE SetPort (port : WindowPtr); 
   CODE CX; QuickDrawModNum; 4 END SetPort;
 
PROCEDURE PortSize (width, height : INTEGER); 
   CODE CX; QuickDrawModNum; 8 END PortSize;
  
PROCEDURE TextFont (font : INTEGER); 
   CODE CX; QuickDrawModNum; 32 END TextFont;
   
PROCEDURE TextSize (size : INTEGER); 
   CODE CX; QuickDrawModNum; 35 END TextSize;
   
PROCEDURE NewWindow (wStorage : Ptr;  boundsRect : Rect;
                     title : Str255;  visible : BOOLEAN;
      theProc:INTEGER; behind : WindowPtr;
      goAwayFlag:BOOLEAN; refCon:LongCard) : WindowPtr; 
   CODE CX; ToolBoxModNum; 50 END NewWindow;

PROCEDURE DrawGrowIcon (theWindow : WindowPtr); 
   CODE CX; ToolBoxModNum; 64 END DrawGrowIcon;
   
PROCEDURE SelectWindow (theWindow : WindowPtr); 
   CODE CX; ToolBoxModNum; 56 END SelectWindow;

BEGIN
WITH WrefCon DO h := 0; l := 0 END;
WITH behind DO h := 65535; l := 65535 END;
WITH OnHeap DO h := 0; l := 0 END;
WITH Wbounds DO top := 50; left := 20; bottom := 300; right := 500 END;
StrModToMac (Wtitle, “Demo Window”); TextFont(0); TextSize(12);
Wnew := NewWindow(Ptr(OnHeap),Wbounds,Wtitle,TRUE,0,
                  WindowPtr(behind),TRUE,WrefCon);
SetPort(Wnew); SelectWindow(Wnew); DrawGrowIcon(Wnew);
PortSize(464,234); ClearScreen; TextFont(3); TextSize(9);
WriteString(“Initialization values for a: “); ReadReal(p);
WriteString(“, and b: “); ReadReal(q); WriteLn;

FOR i:= 1 TO 20 DO
 FOR j:= 1 TO 30 DO
 a[i][j] := p; b[j][i] := q 
 END
END;
WriteString (“Initialization done.”); WriteLn;

FOR i:= 1 TO 30 DO
 FOR j:= 1 TO 30 DO
 sum := 0.0;
 FOR k := 1 TO 20 DO sum:=sum + a[k][i]*b[j][k]  END;
 c[i][j] := sum
 END
END;

WriteString (“Multiplication completed.”); WriteLn;
WriteString (“ C[15,16] = “); GWriteReal (c[15][16],10);
ReadReal(p)

END Matmul.

 

Community Search:
MacTech Search:

Software Updates via MacUpdate

How to get coins faster in Rodeo Stamped...
There comes a time in a cowboy or cowgirl's life when all the riding and lassoing skills in the world aren't enough. You're going to need some cold, hard cash to keep your sky zoo expanding in Rodeo Stampede. [Read more] | Read more »
How to out-do Cam Newton in Can You Dab?
The thing about dance crazes is that you're never really sure when they've run their course. Take the Dab, for instance. Propelled by its adoption as the touchdown celebration of choice for Carolina Panthers quarterback Cam Newton, the Dab seemed... | Read more »
Artik Games releases Splashy Cats for An...
Splashy Cats had us hooked from the title alone, and when we found out the game was literally just zig-zagging one of our favourite pop-culture references, guised as a playable cat character, down a river – our appetites were whetted to say the... | Read more »
Battle Cars (Games)
Battle Cars 1.1 Device: iOS Universal Category: Games Price: $1.99, Version: 1.1 (iTunes) Description: Welcome to the world of Battle Cars. Battle Cars is a classic arcade top-down racing game with fast mini cars and funny weapons to... | Read more »
How to get started with live.ly
One could be forgiven for thinking that there are already plenty of streaming video apps out there. It's just that the App Store charts would insist that you're mistaken. [Read more] | Read more »
Rodeo Stampede: Guide to all Savannah an...
A "gotta catch 'em all" joke seems appropriate here, even though we're talking animals in Rodeo Stampede and not pocket monsters. By now you've probably had plenty of rides, tamed some animals and built yourself a pretty nice zoo | Read more »
Is there cross-platform play in slither....
So you've sunken plenty of hours into crawling around in slither.io on your iPhone or iPad. You've got your stories of tragedy and triumph, the times you coiled four snakes at one time balanced out by the others when you had a length of more than... | Read more »
Rodeo Stampede guide to running a better...
In Rodeo Stampede, honing your skills so you can jump from animal to animal and outrun the herd as long as possible is only half the fun. Once you've tamed a few animals, you can bring them home with you. [Read more] | Read more »
VoxSyn (Music)
VoxSyn 1.0 Device: iOS Universal Category: Music Price: $6.99, Version: 1.0 (iTunes) Description: VoxSyn turns your voice into the most flexible vocal sound generator ever. Instantly following even subtle modulations of pitch and... | Read more »
Catch Battleplans on Google Play from Ju...
Real-time strategy title Battleplans is due for release on Google Play on June 30th, following its release for iOS systems last month. With its simple interface and pretty graphics, the crowd-pleaser brings a formerly overlooked genre out for the... | Read more »

Price Scanner via MacPrices.net

MacBook Airs on sale for up to $50-$100 off M...
B&H Photo has 13″ and 11″ MacBook Airs on sale for up to $100 off MSRP. Shipping is free, and B&H charges NY sales tax only: - 11″ 1.6GHz/128GB MacBook Air: $849 $50 off list price - 11″ 1.... Read more
Brexit Vote Result Forecast To Slash UK 2016...
Uncertainty and economic volatility can be expected to increase over the next nine months, as the Brexit and concerns over the future of the EU hit IT investment, say Canalys market analysts, with... Read more
13-inch 256GB MacBook Air on sale for $1149,...
Amazon has the 2016 13″ 1.6GHz/256GB MacBook Air (model MMGG2LL/A) on sale for $1149.99 including free shipping. Their price is also $50 off MSRP. Read more
Haven App Launches New Age Of Wirless 911 Eme...
Haven from RapidSOS represents a transformation in access to emergency services from a phone call solely dependent on voice to a robust data connection for voice, text, medical/demographic data.... Read more
Cu Parachute 1.1 Retirement Success PLanning...
Tucson, Arizona based Indie developer Bradley McCarthy has announce the release of Cu (Copper) Parachute 1.1 for iPhone, iPad, and iPod touch devices — a tool with which users can continuously... Read more
Research and Markets Releases iPhone 6s Plus...
A new analysis report from Dublin-based Research and Markets observes that with the iPhone 6s Plus, Apple introduced a new rear camera module. The new device has similar structure and technology than... Read more
Apple refurbished Retina MacBook Pros availab...
Apple has Certified Refurbished 2015 13″ and 15″ Retina MacBook Pros available for up to $380 off the cost of new models. An Apple one-year warranty is included with each model, and shipping is free... Read more
Apple refurbished 11-inch MacBook Airs availa...
Apple has Certified Refurbished 11″ MacBook Airs (the latest models), available for up to $170 off the cost of new models. An Apple one-year warranty is included with each MacBook, and shipping is... Read more
Apple price trackers, updated continuously
Scan our Apple Price Trackers for the latest information on sales, bundles, and availability on systems from Apple’s authorized internet/catalog resellers. We update the trackers continuously: - 15″... Read more
12-inch 32GB and 128GB WiFi iPad Pros on sale...
B&H Photo has 12″ 32GB & 128GB WiFi iPad Pros on sale for up to $80 off MSRP, each including free shipping. B&H charges sales tax in NY only: - 12″ Space Gray 32GB WiFi iPad Pro: $749 $50... Read more

Jobs Board

*Apple* iPhone 6s and New Products Tester Ne...
…we therefore look forward to put out products to quality test for durability. Apple leads the digital music revolution with its iPods and iTunes online store, Read more
*Apple* iPhone 6s and New Products Tester Ne...
…we therefore look forward to put out products to quality test for durability. Apple leads the digital music revolution with its iPods and iTunes online store, Read more
*Apple* Retail - Multiple Positions, Willow...
Job Description: Sales Specialist - Retail Customer Service and Sales Transform Apple Store visitors into loyal Apple customers. When customers enter the store, Read more
*Apple* iPhone 6s and New Products Tester Ne...
…we therefore look forward to put out products to quality test for durability. Apple leads the digital music revolution with its iPods and iTunes online store, Read more
*Apple* iPhone 6s and New Products Tester Ne...
…we therefore look forward to put out products to quality test for durability. Apple leads the digital music revolution with its iPods and iTunes online store, Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.