TweetFollow Us on Twitter

Apr 89 Letters
Volume Number:5
Issue Number:4
Column Tag:Letters


By David E. Smith, Editor & Publisher, MacTutor

Aztec C

Rich Heady

San Diego, CA

Aztec C is all I was told it would be, and I’m already pleased with the results. It is particularly gratifying to have access to “intermediate code” again after being locked inside Lightspeed C’s projects for the past 18 months, and more gratifying still to find the assembly code already optimized to the point where I may not need to go through cleaning up the little stupidities. There is nothing wrong with Lightspeed C; in fact, it remains a superior prototyping environment. But at the point where I began to look beyond the prototype to a shippable product, it was a relief to find Aztec C ready to finish the job. Aztec C might carve a bigger niche in the Macintosh world by appealing to the “1 Meg programmer” who wants to produce polished code without larding on RAM and without wading into the complexity of MPW.

Typos upon Typos

Ajay Nath

Oakland Gardens, NY

I’ve been writing a driver for my plotter, and I’ve been looking at the code you presented in MacTutor, Volume 3, Number 11 and 12. I’ve caught some errors in the code you presented on page 57 (#12). The code in the procedure DrvrStorage():


asm {
 MOVEQ  #8, D0
 MOVE.L UTableBase, A0
 MOVE.L (A0), OutDctlEntry

I wrote to you about this error before, but you printed my correction incorrectly! (You did print my explanation of why the author’s code was wrong correctly.) [Sorry, we will double our efforts. -ed]

On page 59 in the procedure MyPrDlgMain() at the end of this proc a pointer is freed and then accessed as follows:

/* 2 */

free(+p); /*ptr is being freed by a subroutine */
if (tp->fDolt) (void) MyPrValidate(hPrint);
 /*we accessed the ptr we freed */
return (tp->fDolt); /* you did it again! */

if (tp->fDolt) is true the subroutine “MyPrValidate” will be called, and it calls traps like GetResource and LoadResource which will move memory so that doing a subsequent “return(tp->fDolt)” may be pointing to garbage.

One way to fix this is to do the following:

/* 3 */

{ Boolean theResult; 
 /* a local variable to hold function result */
theResult = tp->fDolt; /*save the value of fDolt */
free (tp);
if (theResult) (void) MyPrValidate(hPrint);
return (theResult);

on page 58 in the procedure “MyPrintDefault(hPrint)” one of the lines:

**hPrint = **theDefault;

the same line appears on page 59 near the end of the procedure MyPrValidate(hPrint)

What the author is trying to do is to fill in the fields of the data structure that hPrint points to, what he actually does is mess up the hPrint handle. What he should do is something like this:

/* 4 */
BlockMove(*theDefault, *hPrint, sizeof(TPrint));

and probably:

/* 5 */

 /* unload resource now that we’re done */

It is a good article which provides information on how to write printer drivers, but some of the code is incorrect.

In MacTutor, Vol. 4, #11, the code presented by Donald Koscheka to do a string comparison uses the “DBRA” instruction incorrectly. When you loop using “DBRA” you use the word (16 bits) in the register you use as a loop counter; Mr. Koscheka uses register D1 as his loop counter and sets its value by doing:

 MOVE.B (A))+, D1; get length of string 1

This sets the lower 8 bits of D1, NOT the lower word. The correct way to load the value of the loop counter in this case is to:


            MoveQ #0, D0; set D0 = 0;
            Move.B(A0)+, D0      ; D0 = string length

Also when using the “DBRA” instruction, the register must actually have the loop count -1 in it, i.e. if you want to loop 10 times, put 9 in the register. Mr. Koscheka doesn’t do this. I realize that he was showing a code fragment, but the purpose of his article was to show how to use assembly language and allowing such errors to slip in does readers a disservice.

FORTRAN Math Libraries

Michael M. J. Tracy

Pittstown, NJ

I am writing in response to Tatsuhito Koya’s request (Feb 1989, Vol. 5 No. 2) for information on FORTRAN math libraries that will run on the Mac. There is an excellent book out called ‘Numerical Recipes: The Art of Scientific Computing’ by William H. Press, Brian P. Flannery, Saul A. Teukolsky & William T. Vetterling (Cambridge University Press, ISBN 0 521 30811 9). I refer to this book infinitely more often than ‘Inside Macintosh’ when writing scientific applications on the Mac (and it’s cheaper too, about $35 hard cover). The book provides the source code for over 200 subroutines. Its real value to the user, however, is in the eloquent and intelligent discussion of the principles underlying each algorithm, explaining the strengths and weaknesses, and usually providing alternative algorithms so that the cautious user can cross check results. I have learned a lot from this book. Listing from the contents page, the book covers; solution of linear algebraic equations; interpolation and extrapolation; integration of functions; evaluation of functions; special functions; random numbers; sorting; root finding and non-linear sets of equations; minimization and maximization of functions; eigensystems; fourier transform spectral methods; statistical description of data; modeling of data; integration of ordinary differential equations; two point boundary value problems; partial differential equations. There are two versions of the book. The original edition gave the subroutine listings in both FORTRAN and Pascal. By popular demand, a second version was released which presents the C source code listings (written somewhat from the perspective of a FORTRAN programmer who wishes to convert to C, and provides structures and functions for handling complex numbers). Macintosh compatible disks containing the source code are also available from the publishers.

All FORTRAN subroutines that I have used work well, and have compiled without any problems under both MacFortran and Language Systems Fortran. Some subroutines, however, need to have the ‘SAVE’ statement added at the beginning (as required by the ANSI 77 FORTRAN standard) if local variables need to be preserved between subroutine calls, such as in the random number generators.

Further Optimizations

John F. Reiser

Beaverton, OR

The code for optimized string comparisons (Letters, Jan. ’89, p. 106) is on the right track, but the listing contains a bug and the inner loop can be improved further. If the length of the first string is 128 or more, then the iteration count in register D1 gets an incorrect value via sign extension using EXT.W. The loop can be shortened by combining the break-out test with the iteration count control:


A0 -> Pascal string 1
A1 -> Pascal string 2
D0 <- 0 if not equal, 1 if equal

CompareString  Moveq #0,D0; clear high bits
 Move.B (A0), D0 ; length of first string
@10Cmp.B(A0)+, (A1)+ ; mismatch?
 Dbne D0, @10  ; stop when .ne., or at end
 Sne  D0; D0.B = -1 if .ne.; 0 if .eq.
 Addq.B #1, D0 ; D0.B = 0 if .ne.; 1 if .eq.
 Ext.W  D0; Dbne can set bits 7-15

VBL Animation Problems

David Oster

Berkeley, CA

I am appalled by Dick Chandler’s article, “VBL Task Animation” in the February 1989 issue of MacTutor. Yes, his program works, but only because it is a top. Any real program that tries the technique he describes will fail miserably.

Look, his VBL task calls GetIcon and PlotIcon at VBL interrupt time. In his application, the main loop just busy waits for the user to press the Button. A real application would be calling GetNextEvent(), or doing something. For example, each time the user looks at a menu. When the menu goes away, it slams those bits back and deallocates the handle.

GetIcon calls GetResource(). What if the VBL task calls it while the Memory Manager is shuffling the heap to allocate memory for the main loop. Crash city. PlotIcon calls CopyBits(), which clips against the clipRgn and visRgn of the underlying grafPort. What if the VBL task calls it while the Memory Manager is shuffling the heap to allocate memory for the main loop? Crash city.

Even if your program is clean, you do not know what trap patches the user has installed: Maybe he is using an INIT that overrides some trap your program needs, and the override will do memory allocation. For example, Dick’s program calls Button() from its main loop, and many INITs override button, so they will get called while the mouse is down.

So, you can only do animation at interrupt time if you can guarantee that no user or system task will allocate memory in the main loop.

Dick’s program doesn’t guarantee this, since it calls Button() from its main loop, and Button() may have been overriden by an INIT. Since there is so little the main loop can safely do, you might as well give up on VBL Task animation, and just do animation in your main loop, busy waiting until TickCount changes to pause between animation frames.

TWindow Manager Update

Thomas Fruin

Las Condes, Santiago, Chile

After a four month trek through the Latin American country of Peru (that left me penniless), I was delighted upon arrival at my fathers place in Santiago de Chile to find last December’s copy of MacTutor with my Tool Window Manager article. And the generous cheque that was included couldn’t have come at a better time!

Since the article was sent off to you, several programs have been written making use of TWindow. This caused a few small bugs to surface. I would like to take this opportunity to correct them.

The TWindow Manager incorrectly assumes that the calling application will always process every activate or deactivate event by calling TGetNextEvent. However, when multiple dialog boxes are put up, or dialogs following other dialogs without a call to TGetNextEvent in between, some activate or deactivate events may “linger”. This may cause the wrong (de)activation to occur when TGetNextEvent finally is called.

My solution is a utility function FlushActivateEvents(), with the following code:

/* 8 */

static void FlushActivateEvents()

 toBeActivated = toBeDeactivated = nil;
 result = GetNextEvent(activMask, &theEvent);
 result = GetNextEvent(activMask, &theEvent);

When called, this function effectively flushes (removes) every activate and deactivate event from the system: both official events and TWindow Manager internal events.

A call to FlushActivateEvents needs to be inserted in THideWindow and another call in TShowWindow. Both these calls should be made right after the very first if statement, where is checked if the window is still visible or invisible. That is all.

A minor oversight is that the WindowExists function is not defined static. It should be because it is internal to the TWindow Manager.

Finally, I can announce that I have written an MPW Pascal INTERFACE unit, that allows you to call the TWindow Manager from MPW pascal programs. This required more small modifications to the TWindow Manager source. As soon as I get someone to send me my disks from Holland, I will send the new versions of the software to MacTutor. By the way, this version of software also includes a TWaitNextEvent (although this is a trivial addition).

Publication of my article has definitely encouraged me to write more, so expect to see other stuff from me!

Absoft MacFortran to LS Fortran

Bert Waggoner

Riverside, CA

After over a year of reading your journal and programming the Macintosh things are beginning to make a little sense. Now I’d like to give a little back. Here are some notes on the new Language Systems Fortran compiler for MPW that you may wish to pass on to other readers:

I just received the Language Systems (LS) Fortran compiler v1.2 for MPW, and it looks very good. Now, using MPW, I can code in C and have access to the vast array of scientific subroutines written in Fortran (including those of my boss, who is reluctant to learn another language. We are developing chemical transport models for the Macintosh, and, until now, I have been translating his Fortran code to Think C. Microsoft C and Fortran for the IBM PC’s have been on speaking terms for some time - it’s about time the Mac caught up).

Here are some changes I had to make to get an Absoft MacFortran program to compile with LS Fortran:

- the preconnected file units for screen and printer I/O are reversed!

- any WHILE ( )/REPEAT loops must be replaced by DO WHILE ( )/END DO,

- LS Fortran doesn’t have a SELECT CASE statement (sigh),

- IF statements must have enclosing parentheses, i.e. use IF (X .EQ. Y) THEN, not IF X .EQ. Y Then,

- the ACCEPT statement must specify a format,

- there were several differences in filing handling, such as no POSITION or ACCESS key words for the OPEN statement IN LS Fortran.

There are, undoubtably, many other differences. As for toolbox access, LS Fortran’s implementation is different and cleaner, and the language allows for structures. Last, but not least, LS Fortran has a decent manual with lots of examples. Now my problem is converting my Think C code to MPW C. Would any readers like to share their experiences with this?

SysEnvirons From MacFortran

James Wishart

Long Island, NY

In the course of developing an instrument control and data acquisition application in Absoft MacFortran/020, I needed to call SysEnvirons to check for the 68881 floating point processor. Unfortunately, Absoft did not include the trap dispatch parameter for the call in their include files. With the help of additional documentation on the Toolbx.sub routine provided by Lee Rimar of Absoft, I found the correct parameter to be z’09014010'. The following program demonstrates how to call SysEnvirons in Absoft MacFortran.

c 9

program TestSysEnvirons
implicit none

integer*4 toolbx
integer*2 oserr, i
integer*4 version

integer*1 SysEnvRec(16)

integer*2 environsVersion
integer*2 machineType
integer*1 systemVersion(2)
integer*2 processor
logical*1 hasFPU
logical*1 hasColorQD
integer*2 keyBoardType
integer*2 atDrvrVersNum
integer*2 sysVRefNum

equivalence (SysEnvRec(1), environsVersion)
equivalence (SysEnvRec(3), machineType)
equivalence (SysEnvRec(5), systemVersion(1))
equivalence (SysEnvRec(7), processor)
equivalence (SysEnvRec(9), hasFPU)
equivalence (SysEnvRec(10), hasColorQD)
equivalence (SysEnvRec(11), keyBoardType)
equivalence (SysEnvRec(13), atDrvrVersNum)
equivalence (SysEnvRec(15), sysVRefNum)

Parameter (SYSENVIRONS = Z’09014010')
oserr = 0
version = 2
do (i=1,16)
 SysEnvRec(i) = 0

oserr=toolbx(SYENVIRONS, version, SysEnvRec)

if (oserr .ne. -5501) then
 write(9,*) ‘environsVersion = ‘, environsVersion
 write(9,*) ‘machineType = ‘, machineType
 write(9,1) systemVersion(1), systemVersion(2)
1format(‘systemVersion = ‘, z2, “.”, z2)
 write(9,*) ‘processor = ‘, processor
 write(9,*) ‘hasFPU = “, hasFPU
 write(9,*) ‘hasColorQD = ‘, hasColorQD
 write(9,*) ‘keyBoardType = ‘, keyBoardType
 write(9,*) ‘atDrvrVersNum = ‘, atDrvrVersNum
 write(9,*) ‘sysVRefNum = ‘,sysVRefNum
select case (oserr)
 case (0)
 case (-5500)
 write(9,*) ‘System version is less than 4.2’
 case (-5501)
 write(9,*) ‘Bad version selector - no data returned’
 case (-5502)
 write(9,*) ‘Version ‘, version,’ requested, version ‘,
+environsVersion, ‘ returned.’
 case default
 write(9,*) ‘Unspecified error #’, oserr
end select

write(9,*) ‘Hit RETURN to exit program’

A Usenet message from David Phillip Oster brought my attention to the fact that programs should watch for disk insertion events in their main loops and call DIBadMount if the inserted disk cannot be mounted. Implementing this feature requires two more undocumented trap dispatch parameter, DIBadMount (z’9E952200', routine #0) and DIUnload (z’9E908000', routine #4) from Pack2, Disk Initialization. The following code fragment uses the event manager variables defined in the example in the MacFortran manual. (Notice that the Pack2 routine selector must be added to the end of the argument list.) See Inside Macintosh Vol. 2 for the result codes returned in the two byte variable err.

c 10

select case (what)
 case(7)! 7 = Disk insertion
 if (shift(message, -16) .ne. 0) then
 call toolbx(INITCURSOR)
 err = toolbx(DIBADMOUNT, z’00640064', message, 0)
 call toolbx(DIUNLOAD, 4)

The remaining Pack2 parameters should be as follows, but I have not tested these: DILoad: z’9E908000', routine #2; DIFormat: z’9E949000', routine #6; DIVerify: z’9E949000', routine #8; DIZero: z’9E94E200' or z’9E94C200', routine #10.

I want to thank Jay Lieske for his “Fortran Printing Interface” article in August, 1988 issue as well as all of the people who contributed information about Classic Mac analog board failures. Every month I pace in front of my mailbox until MacTutor arrives.

Author Incentive Program Correction

Kirk Chase

Anaheim, CA

In the December ’89 MacTutor, we made a correction on the Author Incentive Program initiated by Apple. Additional reimbursement is ONLY FOR APPLE EMPLOYEES. Those not employed by Apple DO NOT QUALIFY. We are sorry for any confusion that may have resulted over this and hope this clears up any mistaken notions. If you are with Apple, and if you want more information, please contact Stacey Farmer in public relations, who is now in charge of the program, for more information.

Apple Inc.
Microsoft Corpora
Google Inc.

MacTech Search:
Community Search:

Software Updates via MacUpdate

NTFS 12.0.39 - Provides full read and wr...
Paragon NTFS breaks down the barriers between Windows and OS X. Paragon NTFS effectively solves the communication problems between the Mac system and NTFS, providing full read and write access to... Read more
RestoreMeNot 2.0.3 - Disable window rest...
RestoreMeNot provides a simple way to disable the window restoration for individual applications so that you can fine-tune this behavior to suit your needs. Please note that RestoreMeNot is designed... Read more
Macgo Blu-ray Player - Blu-r...
Macgo Mac Blu-ray Player can bring you the most unforgettable Blu-ray experience on your Mac. Overview Macgo Mac Blu-ray Player can satisfy just about every need you could possibly have in a Blu-ray... Read more
Apple iOS 8.1 - The latest version of Ap...
The latest version of iOS can be downloaded through iTunes. Apple iOS 8 comes with big updates to apps you use every day, like Messages and Photos. A whole new way to share content with your family.... Read more
TechTool Pro 7.0.5 - Hard drive and syst...
TechTool Pro is now 7, and this is the most advanced version of the acclaimed Macintosh troubleshooting utility created in its 20-year history. Micromat has redeveloped TechTool Pro 7 to be fully 64... Read more
PDFKey Pro 4.0.2 - Edit and print passwo...
PDFKey Pro can unlock PDF documents protected for printing and copying when you've forgotten your password. It can now also protect your PDF files with a password to prevent unauthorized access and/... Read more
Yasu 2.9.1 - System maintenance app; per...
Yasu was originally created with System Administrators who service large groups of workstations in mind, Yasu (Yet Another System Utility) was made to do a specific group of maintenance tasks... Read more
Hazel 3.3 - Create rules for organizing...
Hazel is your personal housekeeper, organizing and cleaning folders based on rules you define. Hazel can also manage your trash and uninstall your applications. Organize your files using a... Read more
Autopano Giga 3.7 - Stitch multiple imag...
Autopano Giga allows you to stitch 2, 20, or 2,000 images. Version 3.0 integrates impressive new features that will definitely make you adopt Autopano Pro or Autopano Giga: Choose between 9... Read more
MenuMeters 1.8 - CPU, memory, disk, and...
MenuMeters is a set of CPU, memory, disk, and network monitoring tools for Mac OS X. Although there are numerous other programs which do the same thing, none had quite the feature set I was looking... Read more

Latest Forum Discussions

See All

Inferno 2 Review
Inferno 2 Review By Andrew Fisher on October 21st, 2014 Our Rating: :: TWIN STICK GOODNESSUniversal App - Designed for iPhone and iPad With tight controls and awesome, stark visuals, Inferno 2 is loads of fun.   | Read more »
Clips Review
Clips Review By Jennifer Allen on October 21st, 2014 Our Rating: :: CONVENIENT PASTINGUniversal App - Designed for iPhone and iPad Making copying and pasting more powerful than usual, Clips is a great way to move stuff around.   | Read more »
MonSense Review
MonSense Review By Jennifer Allen on October 21st, 2014 Our Rating: :: ORGANIZED FINANCESiPhone App - Designed for the iPhone, compatible with the iPad Organize your finances with the quick and easy to use, MonSense.   | Read more »
This Week at 148Apps: October 13-17, 201...
Expert App Reviewers   So little time and so very many apps. What’s a poor iPhone/iPad lover to do? Fortunately, 148Apps is here to give you the rundown on the latest and greatest releases. And we even have a tremendous back catalog of reviews; just... | Read more »
Angry Birds Transformers Review
Angry Birds Transformers Review By Jennifer Allen on October 20th, 2014 Our Rating: :: TRANSFORMED BIRDSUniversal App - Designed for iPhone and iPad Transformed in a way you wouldn’t expect, Angry Birds Transformers is a quite... | Read more »
GAMEVIL Announces the Upcoming Launch of...
GAMEVIL Announces the Upcoming Launch of Mark of the Dragon Posted by Jessica Fisher on October 20th, 2014 [ permalink ] Mark of the Dragon, by GAMEVIL, put | Read more »
Interview With the Angry Birds Transform...
Angry Birds Transformers recently transformed and rolled out worldwide. This run-and-gun title is a hit with young Transformers fans, but the ample references to classic Transformers fandom has also earned it a place in the hearts of long-time... | Read more »
Hail to the King: Deathbat Review
Hail to the King: Deathbat Review By Rob Thomas on October 20th, 2014 Our Rating: :: SO FAR AWAYUniversal App - Designed for iPhone and iPad Hail to the King: Deathbat may feel like “Coming Home” for Avenged Sevenfold’s faithful,... | Read more »
Find Free Food on Campus with Ypay
Find Free Food on Campus with Ypay Posted by Jessica Fisher on October 20th, 2014 [ permalink ] iPhone App - Designed for the iPhone, compatible with the iPad | Read more »
Strung Along Review
Strung Along Review By Jordan Minor on October 20th, 2014 Our Rating: :: GOT NO STRINGSUniversal App - Designed for iPhone and iPad A cool gimmick and a great art style keep Strung Along from completely falling apart.   | Read more »

Price Scanner via

Strong iPhone, Mac And App Store Sales Drive...
Apple on Monday announced financial results for its fiscal 2014 fourth quarter ended September 27, 2014. The Company posted quarterly revenue of $42.1 billion and quarterly net profit of $8.5 billion... Read more
Apple Posts How-To For OS X Recovery
OS X 10.7 Lion and later include OS X Recovery. This feature includes all of the tools you need to reinstall OS X, repair your disk, and even restore from a Time Machine backup. OS X Recovery... Read more
Mac OS X Versions (Builds) Supported By Vario...
Apple Support has posted a handy resource explaining which Mac OS X versions (builds) originally shipped with or are available for your computer via retail discs, downloads, or Software Update. Apple... Read more
Deals on 2011 13-inch MacBook Airs, from $649
Daily Steals has the Mid-2011 13″ 1.7GHz i5 MacBook Air (4GB/128GB) available for $699 with a 90 day warranty. The Mid-2011 13″ 1.7GHz i5 MacBook Air (4GB/128GB SSD) is available for $649 at Other... Read more
2013 15-inch 2.0GHz Retina MacBook Pro availa...
B&H Photo has leftover previous-generation 15″ 2.0GHz Retina MacBook Pros now available for $1599 including free shipping plus NY sales tax only. Their price is $400 off original MSRP. B&H... Read more
Updated iPad Prices
We’ve updated our iPad Air Price Tracker and our iPad mini Price Tracker with the latest information on prices and availability from Apple and other resellers, including the new iPad Air 2 and the... Read more
Apple Pay Available to Millions of Visa Cardh...
Visa Inc. brings secure, convenient payments to iPad Air 2 and iPad mini 3as well as iPhone 6 and 6 Plus. Starting October 20th, eligible Visa cardholders in the U.S. will be able to use Apple Pay,... Read more
Textkraft Pocket – the missing TextEdit for i...
infovole GmbH has announced the release and immediate availability of Textkraft Pocket 1.0, a professional text editor and note taking app for Apple’s iPhone. In March 2014 rumors were all about... Read more
C Spire to offer iPad Air 2 and iPad mini 3,...
C Spire on Friday announced that it will offer iPad Air 2 and iPad mini 3, both with Wi-Fi + Cellular, on its 4G+ LTE network in the coming weeks. C Spire will offer the new iPads with a range of... Read more
Belkin Announces Full Line of Keyboards and C...
Belkin International has unveiled a new lineup of keyboard cases and accessories for Apple’s newest iPads, featuring three QODE keyboards and a collection of thin, lightweight folios for both the... Read more

Jobs Board

*Apple* Solutions Consultant (ASC) - Apple (...
**Job Summary** The ASC is an Apple employee who serves as an Apple brand ambassador and influencer in a Reseller's store. The ASC's role is to grow Apple Read more
Project Manager / Business Analyst, WW *Appl...
…a senior project manager / business analyst to work within our Worldwide Apple Fulfillment Operations and the Business Process Re-engineering team. This role will work Read more
*Apple* Retail - Multiple Positions (US) - A...
Job Description: Sales Specialist - Retail Customer Service and Sales Transform Apple Store visitors into loyal Apple customers. When customers enter the store, Read more
Position Opening at *Apple* - Apple (United...
…customers purchase our products, you're the one who helps them get more out of their new Apple technology. Your day in the Apple Store is filled with a range of Read more
Position Opening at *Apple* - Apple (United...
**Job Summary** At the Apple Store, you connect business professionals and entrepreneurs with the tools they need in order to put Apple solutions to work in their Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.