TweetFollow Us on Twitter

Dec 89 Letters
Volume Number:5
Issue Number:12
Column Tag:Letters

Letters

By David E. Smith, Editor & Publisher, MacTutor

There IS an OOP Book

James Plamondon

San Mateo, CA

I have just received and read my copy of the September issue of MacTutor, and was pleased to discover that it was up to its usual high standards. Unfortunately, I was horrified to see one piece of misinformation presented -- however unintentionally -- as fact, when the truth could be of great use to your readership.

In the article MacOOPs!, by Jean-Denis Muys-Vasovic, on page 102, in the first paragraph, the author says that “Algorithms + Data Structures = Programs”, by Niklaus Wirth, was the book that established the case for structured programming in the seventies. This is entirely correct.

Unfortunately, the author goes on to say that ‘This technology [OOP] has not yet got its “Algorithms + Data Structures = Programs” ’, meaning that there is not yet any single book on OOP that explains its concepts, advantages, implementation, and so on. This statement has not been true for more than a year.

Everyone who has an interest in OOP should run -- not walk -- to the nearest computer bookstore and buy a copy of Bertrand Meyer’s book, “Object-Oriented Software Construction”, published in 1988 by Prentice Hall (about $40). It is without a doubt the most comprehensive, concise, and yet readable book on Object-Oriented Design and Programming to date -- and I have no doubt that it will soon be considered to be as important to the success of OOP as Wirth’s book was to structured programming.

Just as Wirth’s book explained and made the case for block structuring, strong typing, and functional decomposition, Meyer’s book explains and makes the case for object-oriented design, based on considerations of correctness, robustness, extendibility, reusability, and compatibility. Meyer’s book, like Wirth’s, combines the rigorous precision of computer science with the practical aspects of software engineering. Wirth used his own, new language, Pascal, to present his ideas, because the other languages of the time were inadequate. Likewise, Meyer uses his own language, Eiffel, to present his ideas, because no other existing language so elegantly addresses both the theoretical and practical issues of object-oriented design.

Pascal went on to become one of the major computer languages of the seventies and eighties, due to its close association with structured programming. Its commercial use was hampered by the fact that it was designed to be a teaching aid, not a language for software engineering. Eiffel, on the other hand, was designed from the first to be a practical tool for the development of commercial software. Its future is unlimited.

In every discipline, its practitioners struggle for years on the fringes of great breakthroughs -- gravity, natural selection, relativity, plate tectonics -- until some author comes along and puts it all together. That is what Wirth did for structured programming, and that is what Meyer has done for object-oriented programming. I was a geologist during the battles that led to the acceptance of plate tectonics, so I’ve learned to recognize a paradigm shift when I see one.

If knowledge is power, and the future of programming is OOP, then this book will give you the power to control the future of programming. Take the day off, grab the company credit card, go to the nearest computer bookstore, buy Meyer’s book, and don’t listen to another word about OOP until you’re done reading it.

Stop reading this letter! Get moving! Run!

What, you’re still here?

Virus?

George Patail

APO New York

I am new to Mac programming and an avid reader of MacTutor and need your help regarding Mac viruses and their eradication. My system (a Mac II with an 80MB HD) had a bad case of the “hangs” lasting for 15-20 minutes on bootup and when launching applications. I cleared out all the files and reinstalled them after examining each one with ResEdit. I installed Vaccine on my system and it seems to keep a vigilant eye on any attempts to add additional CODE resources. It warns me and asks for the usual permission to let it add or deny access to the CODE resource.

However running LS Pascal 2.0, it asks for permission with the usual message for every source file I try to add to a project. I launched ResEdit and examined my System Folder for any telltale signs of Scores or nVIR viruses following Max Rochlin’s instructions (Mousehole Report, MacTutor June 1988). None were found! However, the LS Pascal application’s CODE id=0’s eleventh word displays ‘038A’ and the tenth displays ‘4EED’. According to MaxR this is a sure sign of Scores infection! But I could not locate any additional CODE segments corresponding to 038A which is two higher than the next, nor atpl id 128, data id -4001, inits 6, 10, 17, _Desktop and Scores files in the System Folder. I checked the master LS Pascal 2.0 disks I got from Think and they too display the same anomalies with 4EED and 038A. Is the LS Pascal infected, or is it normal code for LS? Do you think it is a new strain? It does not seem to spread to other applications so far. But I am at a loss as to how to combat this other than turning Vaccine off, which I don’t want to do knowing if it is safe to run LS Pascal. I am stationed in Heidelberg Germany and the local Apple reps could not answer anything beyond the most elementary questions.

[LS Pascal adds code resources to its project file each time you compile, so naturally Vaccine will intercept the attempt to add a code type resource, like CODEs and CDEFs. My copy of LS Pascal also contained the same words in CODE 0. I have been using VIREX by HJC Software and Vaccine before without a hint of virus troubles. A quick call to Symantec said that the jump table is beyond that point and those are the words that should be there. So my opinion is that you don’t have a virus. I would suggest your ‘hangs’ are due to INITs. One of them is likely to be giving you problems.

If you are worried about virus problems, may I suggest that VIREX or another commercial virus program. It is my understanding that Vaccine is not continually updated as other commercial programs. -ed]

To Paul Onstad

John Baxter

Port Ludlow, WA

As others have noted, the solution to Paul Onstad’s question about opening a resource fork in a desired folder is straight forward (especially for those of us who have been “around” the Mac since the early days). Simply save the current default volume with GetVol, then set the default volume to the “volume” (actually a working directory in most cases) returned by the SFPutFile call (or earlier SFGetFile call if replacing a file). Then use the old resource file opening calls without concern. When completed, set the default volume back.

Furthermore, when rewriting a file as a result of Save, it is not necessary to erase the old file. It is sufficient to set the EOF of the data fork to zero before writing the new data. This will leave the resource fork, the creation date, and the position within the folder as seen by Finder unchanged. Only for Save As should it be necessary to copy the resource fork. [It’s actually only necessary to set EOF to the new value, and then only if the old file is larger. if the new EOF value is known before starting to write the data, this might be preferred.] The SetEOF call takes the file’s reference number and the desired new EOF value, extending or truncating the file as needed. Inside Macintosh, Vol. II, pg. 93.

More Paul Onstad

John H. Roth, Jr.

Chicago, IL

Your new cover style almost lost you a reader-I found your August issue on the magazine rack by accident. For a while I thought you had gone under (perish the thought).

By now, you’ve probably got a dozen letters about Paul Onstad’s resource fork problem. The error from OpenRFPerm is because the new resource fork doesn’t have a resource map. This can be corrected by a call to CreateResFile, after the call to Create but before the call to OpenRFPerm. The sequence of calls is crucial; odd things can happen if Create is not called first. This is explained in Tech Note 101.

The basic misconception seems to be that the Create call builds both forks of the file. Actually, it builds an empty directory entry. For the data fork, Open is then sufficient, but for the resource fork, initialization data has to be written into it before the Resource Manager can do its thing.

THINK C 4.0 Bugs

William Modesitt

Kaneohe, HI

There are two known bugs in the new THINK C 4.0. Both involve scanf. When using the standard library ANSI, scanf will not work correctly for float values less than .1. When using the library ANSI_881, scanf in general does not work correctly for float values. I was told by THINK C technical staff that these were the only known bugs, and they were both rather nasty. The fixes are shown below.

Buggy version:

case -2:
 if (c >= ‘0’ && c <= ‘9’) {
 F.valid = TRUE;
 if (c != ‘0’ || D.sig[0]) {
 if (D.sig[0] < sizeof D.sig - 1)
 D.sig[++D.sig[0]] = c;
 if (F.dot)
 --D.exp;
 }
 }

Correct version:

/* 1 */

 if (c >= ‘0’ && c <= ‘9’) {
 F.valid = TRUE;
 if (c != ‘0’ || D.sig[0]) {
 if (D.sig[0] < sizeof D.sig - 1)
 D.sig[++D.sig[0]] = c;
 } /* paren was moved here from two lines below */
 if (F.dot)
 --D.exp;
 }

Buggy version (881):

register struct decrec *d;
void *p;
{
 short  excp class, c = ‘0’;
#ifdef _MC68881_
 register short *q = p;
 
 p = q + 1;
#endif
Correct version (881):
register struct decrec *d;
void *p;
{
 short  excp class, c = ‘0’;
#ifdef _MC68881_
 register short *q = p;
 
 if (code == FFEXT)  /* add this line */
 p = q + 1;
#endif

Buggy version (881):

#ifdef _MC68881_
 q[0] = q[1];
 q[1] = 0;
#endif
 return;

Correct version (881):

/* 2 */

#ifdef _MC68881_
 if (code == FFEXT) { /* add this line */
 q[0] = q[1];
 q[1] = 0;
 } /* add this line */
#endif
 return;

Once these changes have been made, you should “make” all four ANSI libraries by choosing the make option, check scanf.c, then “make” it. Any projects that you have will automatically load the new ANSI library for you next time you update.

And now for something completely different. I have tried to find a way to determine the current volume reference number or working directory reference number for my current application during run time so I can write to it’s data fork. Along the same line, I think, I would like to do the following: Implement SFGetFile, exit, find out where I am, move to the parent directory, and implement SFGetFile again in the new (parent) directory. What I need is a function called “WhereAmI”. Any help would be greatly appreciated.

Linear Equation Error

Wilfred Long, Jr.

Montgomery Village, MD

In C. H. Friend’s Linear Equations True Basic examples from January’s letters column, he couldn’t produced the output shown in the Multiple Linear Regression” segment by running the source as listed. All the errors are on page 109 in the last third of the program following the REM statement depicting how H-P Basic allows solution of the linear system.

In the MAT PRINT USING formatter for “Coefficients” there should be three leading dashes instead of two and the comma should be a period.

The LET statement in the vector dot-product loop following “residuals:” is incomplete-no product is indicated. It should be written either:

LET Y2(I) = Y(I,1) * Y(I,1)

or

LET Y2(I) = Y(I,1)^2

In the second from the last PRINT USING statement, the variable SSR should be SSA in both instances. There is no variable SSR, but SSA produces the value 399.454 shown in the last results-output line attributed to SSR.

Finally, in the last PRINT USING formatter for variable ES2, the comma again should be a period.

There are a couple of incorrect values in the results-output, but they’ll be obvious when the corrected program runs.

Fulfilling A Dream

Natalia Kolodziejska

Wroclaw, Poland

I am an 11-year old Polish schoolgirl dreaming of an Apple Macintosh.

Poland is full of personal computers. There are many Atari, Commodore, IBM and Sinclair/Timex computers.

There also are other computers in use. However, the Apple Macintosh is absent in Poland. Anyway, I was lucky enough to see and use this computer some times. I am sure it would be my best friend.

However, I have a very little chance to come into its possession by myself. I simply lack the proper means. So, perhaps somewhere in the world there are people or institutions that have one superfluous (used) Macintosh which could be donated to me. (I would also welcome a printer and some software.) Please forward this letter to your readers and friends. Everyone can contact me, even if he or she can help me to only some extent.

Using the Macintosh I could better prepare myself for life in the next century.

My best greetings,

Natalia Kolodziejska

ul. Drzewieckiego 16/4

PL 54-129 Wroclaw

Poland

 
AAPL
$102.50
Apple Inc.
+0.25
MSFT
$45.43
Microsoft Corpora
+0.55
GOOG
$571.60
Google Inc.
+2.40

MacTech Search:
Community Search:

Software Updates via MacUpdate

VueScan 9.4.41 - Scanner software with a...
VueScan is a scanning program that works with most high-quality flatbed and film scanners to produce scans that have excellent color fidelity and color balance. VueScan is easy to use, and has... Read more
Cloud 3.0.0 - File sharing from your men...
Cloud is simple file sharing for the Mac. Drag a file from your Mac to the CloudApp icon in the menubar and we take care of the rest. A link to the file will automatically be copied to your clipboard... Read more
LibreOffice 4.3.1.2 - Free Open Source o...
LibreOffice is an office suite (word processor, spreadsheet, presentations, drawing tool) compatible with other major office suites. The Document Foundation is coordinating development and... Read more
SlingPlayer Plugin 3.3.20.505 - Browser...
SlingPlayer is the screen interface software that works hand-in-hand with the hardware inside the Slingbox to make your TV viewing experience just like that at home. It features an array of... Read more
Get Lyrical 3.8 - Auto-magically adds ly...
Get Lyrical auto-magically add lyrics to songs in iTunes. You can choose either a selection of tracks, or the current track. Or turn on "Active Tagging" to get lyrics for songs as you play them.... Read more
Viber 4.2.2 - Send messages and make cal...
Viber lets you send free messages and make free calls to other Viber users, on any device and network, in any country! Viber syncs your contacts, messages and call history with your mobile device,... Read more
Cocktail 7.6 - General maintenance and o...
Cocktail is a general purpose utility for OS X that lets you clean, repair and optimize your Mac. It is a powerful digital toolset that helps hundreds of thousands of Mac users around the world get... Read more
LaunchBar 6.1 - Powerful file/URL/email...
LaunchBar is an award-winning productivity utility that offers an amazingly intuitive and efficient way to search and access any kind of information stored on your computer or on the Web. It provides... Read more
Maya 2015 - Professional 3D modeling and...
Maya is an award-winning software and powerful, integrated 3D modeling, animation, visual effects, and rendering solution. Because Maya is based on an open architecture, all your work can be scripted... Read more
BBEdit 10.5.12 - Powerful text and HTML...
BBEdit is the leading professional HTML and text editor for the Mac. Specifically crafted in response to the needs of Web authors and software developers, this award-winning product provides a... Read more

Latest Forum Discussions

See All

Rhonna Designs Magic (Photography)
Rhonna Designs Magic 1.0 Device: iOS Universal Category: Photography Price: $1.99, Version: 1.0 (iTunes) Description: Want to sprinkle *magic* on your photos? With RD Magic, you can add colors, filters, light leaks, bokeh, edges,... | Read more »
This Week at 148Apps: August 25-29, 2014
Shiny Happy App Reviews   | Read more »
Qube Kingdom – Tips, Tricks, Strategies,...
Qube Kingdom is a tower defense game from DeNA. You rally your troops – magicians, archers, knights, barbarians, and others – and fight against an evil menace looking to dominate your kingdom of tiny squares. Planning a war isn’t easy, so here are a... | Read more »
Qube Kingdom Review
Qube Kingdom Review By Nadia Oxford on August 29th, 2014 Our Rating: :: KIND OF A SQUARE KINGDOMUniversal App - Designed for iPhone and iPad Qube Kingdom has cute visuals, but it’s a pretty basic tower defense game at heart.   | Read more »
Fire in the Hole Review
Fire in the Hole Review By Rob Thomas on August 29th, 2014 Our Rating: :: WALK THE PLANKUniversal App - Designed for iPhone and iPad Seafoam’s Fire in the Hole looks like a bright, 8-bit throwback, but there’s not enough booty to... | Read more »
Alien Creeps TD is Now Available Worldwi...
Alien Creeps TD is Now Available Worldwide Posted by Ellis Spice on August 29th, 2014 [ permalink ] Universal App - Designed for iPhone and iPad | Read more »
Dodo Master Review
Dodo Master Review By Jordan Minor on August 29th, 2014 Our Rating: :: NEST EGGiPad Only App - Designed for the iPad Dodo Master is tough but fair, and that’s what makes it a joy to play.   | Read more »
Motorsport Manager Review
Motorsport Manager Review By Lee Hamlet on August 29th, 2014 Our Rating: :: MARVELOUS MANAGEMENTUniversal App - Designed for iPhone and iPad Despite its depth and sense of tactical freedom, Motorsport Manager is one of the most... | Read more »
Motorsport Manager – Beginner Tips, Tric...
The world of Motorsport management can be an unforgiving and merciless one, so to help with some of the stress that comes with running a successful race team, here are a few hints and tips to leave your opponents in the dust. | Read more »
CalPal Update Brings the App to 2.0, Add...
CalPal Update Brings the App to 2.0, Adds Lots of New Stuff Posted by Ellis Spice on August 29th, 2014 [ permalink ] | Read more »

Price Scanner via MacPrices.net

The Rise of Phablets
Carlisle & Gallagher Consulting Group, a businesses and technology consulting firm focused solely on the financial services industry, has released an infographic depicting the convergence of... Read more
Eddy – Cloud Music Player for iPhone/iPad Fre...
Ukraine based CapableBits announces the release of Eddy, its tiny, but smart and powerful cloud music player for iPhone and iPad that allows users to stream or download music directly from cloud... Read more
A&D Medical Launches Its WellnessConnecte...
For consumers and the healthcare providers and loved ones who care for them, A&D Medical, a leader in connected health and biometric measurement devices and services, has launched its... Read more
Anand Lal Shimpi Retires From AnandTech
Anand Lal Shimpi, whose AnandTech Website is famous for its meticulously detailed and thoroughgoing reviews and analysis, is packing it in. Lal Shimpi, who founded the tech site at age 14 in 1997,... Read more
2.5GHz Mac mini, Apple refurbished, in stock...
The Apple Store has Apple Certified Refurbished 2.5GHz Mac minis available for $509, $90 off MSRP. Apple’s one-year warranty is included, and shipping is free. Read more
13-inch 2.5GHz MacBook Pro on sale for $999,...
B&H Photo has the 13″ 2.5GHz MacBook Pro on sale for $999.99 including free shipping plus NY sales tax only. Their price is $100 off MSRP. Read more
Labor Day Weekend MacBook Pro sale; 15-inch m...
B&H Photo has the new 2014 15″ Retina MacBook Pros on sale for up to $125 off MSRP. Shipping is free, and B&H charges NY sales tax only. They’ll also include free copies of Parallels Desktop... Read more
Labor Day Weekend iPad mini sale; $50 to $100...
Best Buy has the iPad mini with Retina Display (WiFi models) on sale for $50 off MSRP on their online store for Labor Day Weekend. Choose free shipping or free local store pick up. Price is for... Read more
13-inch 1.4GHz MacBook Air on sale for $899,...
Adorama has the new 2014 13″ 1.4GHz/128GB MacBook Air on sale for $899.99 including free shipping plus NY & NJ tax only. Their price is $100 off MSRP. Read more
It’s Official: Apple Issues Invitations To Se...
Apple has issued one of its characteristically cryptic press invitations for a special event to be held at the Flint Center for the Performing Arts in hometown Cupertino on Sept. 9, 2014 at 10:00 am... Read more

Jobs Board

*Apple* Retail - Multiple Positions (US) - A...
Sales Specialist - Retail Customer Service and Sales Transform Apple Store visitors into loyal Apple customers. When customers enter the store, you're also the Read more
*Apple* Retail - Multiple Positions (US) - A...
Sales Specialist - Retail Customer Service and Sales Transform Apple Store visitors into loyal Apple customers. When customers enter the store, you're also the Read more
*Apple* Retail - Multiple Positions (US) - A...
Sales Specialist - Retail Customer Service and Sales Transform Apple Store visitors into loyal Apple customers. When customers enter the store, you're also the Read more
*Apple* Retail - Multiple Positions (US) - A...
Sales Specialist - Retail Customer Service and Sales Transform Apple Store visitors into loyal Apple customers. When customers enter the store, you're also the Read more
Senior Event Manager, *Apple* Retail Market...
…This senior level position is responsible for leading and imagining the Apple Retail Team's global event strategy. Delivering an overarching brand story; in-store, Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.