TweetFollow Us on Twitter

September 93 - Letters

LETTERS

NEW TECH NOTE NUMBERS
In develop Issue 14 Peter Fink complains about the loss of Tech Note numbering. In your answer you write: "We're always open to suggestion, but so far you're the only one to mention this. If others reading this reply have similar feedback, I hope they'll let us know."

Actually, I and others have complained about the loss of Tech Note numbers for quite some time, but sometimes talking about these things is like complaining about the weather. I suspect most people just grumble along and don't complain in writing.
-- Johan G. E. Strandberg

Good news: Numbers are back; see the editorial on page 2 and the Tech Notes on this issue's CD. It's too bad when people grumble without writing; the latter is much more effective, and we really appreciate the effort. Thanks!
-- Caroline Rose

DEBUGGING LESSON FLUB
There seems to be a problem with the point made in the "Debugging Lesson" letter in the Letters section of develop Issue 14. According to the source listed, there would be no problem even if memory moved when FillWithData was called. Since the handle is being passed as a handle (that is, not dereferenced), and handles are 4-byte pointers (which get pushed onto the stack as is), FillWithData would always get a valid handle, which it can dereference internally to its heart's content.

Unfortunately, there seems to be a lot of confusion (and a great deal of paranoia) over the usage of handles. As long as you pass handles as handles (and watch your dereferencing), you'll be OK.
--Charlie Reading

Um, oops. (Imagine, if you will, me standing gaping and red-faced, astonished at my own carelessness and idiocy.)

You're right, of course; the danger is only in passing dereferenced handles to routines in other segments, and the code in the letter passes the handle itself. I guess I just read the text and didn't really look closely at the code before replying. Obviously, it was only intended as an example, and the writer's point is still valid: passing dereferenced handles to routines in other segments is dangerous. You should either pass the handle itself (as the example code did!) or lock the handle first.

Sorry about the confusion.
--Dave Johnson

BABBLING ON
I enjoyed reading Dave Johnson's column in develop Issue 13 ("Tower of Babble"). While reading his discussion of natural versus programming languages, I think I was able to put my finger on what has bugged me about HyperTalk® for years. Natural languages imply a fluidity of meaning, giving its users great flexibility for nuances, emphasis, and brevity. HyperTalk looks like a natural language, but it possesses none of that fluidity of meaning. In HyperCard ®, SET has but one meaning. But in my Oxford dictionary, "set" has 194 definitions! In other words, HyperCard looks so much like English, one winds up assuming that all kinds of structures could be used as long as they make sense in English (for example, "set me to true").

Allow me to submit a suggestion, which you may wish to pass along to the software gods. Since Apple has now all but declared that C and C++ are the only computer languages the human race will ever need, maybe it would be great to have a HyperTalk-to-C translator. Why? Well, C is a write- only language (no one ever can figure out what's happening in someone else's C listing) and HyperTalk is a read-only language (it's a cinch to understand, but impossible to code in). With a translator, we could write code that still could be understood, just like when we used to code in Pascal. (Yes, this is a joke, from a die-hard Pascal enthusiast.) Thanks again for a nifty column!
--Kevin Killion

I'm glad you liked the column. Your comment about HyperTalk is very well taken! I think that's what always bothered me about it, too, though it was just a sort of vague unease. Unfortunately, I think people who didn't learn "regular" programming languages first may have a distinct disadvantage: we "real" programmers know up front how limited and terse and strict programming languages are, and we don't expect anything more. But power users who learn HyperTalk (or, more likely now, AppleScript) as their very first programming language may be in for a struggle if they don't keep reminding themselves that it's not a natural language.

As a die-hard C enthusiast, I'll graciously ignore your slams against my favorite language, and assume that since you're obviously an intelligent person, sooner or later you'll realize the error of your ways and come around to the truth, bemoaning the years you've spent in bondage to an uptight compiler.
--Dave Johnson

ASYNCH SUPPORT ON A/UX
After reading through Jim Luther's Asynchronous Routines article in develop Issue 13, I spiffed up my application to make all my file handling asynchronous, anticipating the glorious day when all the drivers on my Macintosh support asynchronous calls. But since the SCSI Manager isn't asynchronous yet, there's no apparent difference to the user of my code (or to me, the hard-working programmer who wants payoff for my labors).

Is there any platform or configuration I can test my application on and see the results of my effort?
--Tony Amaretto

Try your code on A/UX 3.0.1 (the operating system for the Apple Workgroup Server 95); it features an enhanced File Manager that supports asynchronous calls to UNIX ® file systems simply by using the techniques in Jim Luther's article. AppleShare Pro takes advantage of this capability on AWS 95 to get performance up to four times better than AppleShare 3.0's under System 7 (your mileage, as always, will vary).

For more information related to the Asynchronus Routines article, see the box on the next page. Have fun!
--Dave Johnson

MORE ON ASYNCHRONOUS ROUTINES IN ISSUE 13

For developers interested in the "Asynchronous Routines on the Macintosh" article in develop Issue 13, here's some new information that has surfaced since then.

StackSpace. Contrary to the advice on page 28 of the article, you should not call StackSpace at interrupt time, because the Memory Manager might not be in a consistent state. Furthermore, StackSpace clears MemErr, which may have an adverse effect on the current process's handling of Memory Manager errors.

PPC polling. Unlike the Device Manager and File Manager, the PPC Toolbox stuffs the result of an asynchronous routine into ioResult before it's really done with the parameter block. If your interrupt code -- such as a VBL task -- polls ioResult periodically to check for completion and reuses the parameter block to make another call, the system can crash because one or more system queues will be corrupted.

Context switching. The System 7 Process Manager (and MultiFinder under System 6) will wait until all currently active asynchronous requests to the File Manager have completed before performing a context switch. This check was added for compatibility reasons to prevent system crashes caused by a few applications that accessed program globals within File Manager completion routines without restoring their A5 world. What this means to you is that if your application makes an asynchronous File Manager call and then calls WaitNextEvent or GetNextEvent, the system may wait for your call to complete. If the asynchronous File Manager call takes a long time to complete, it will appear to the user that the system isn't responding.

Synchronous drivers. Although you can execute low-level file access routines asynchronously, a volume's underlying device driver may not support asynchronous operations. Once the File Manager passes a request to a synchronous driver, that driver doesn't give up control until it has completed the task. Synchronous drivers (such as those using the current SCSI Manager) affect programs using asynchronous File Manager calls in two ways: unexpected pauses and unsightly stack frame buildup.

  • When calling the File Manager asynchronously, your program passes control to the File Manager and the request is placed in a queue or, if the queue is empty, the request is handled immediately. Either way, once a synchronous driver gets the request, it retains control until it has responded to the request. If the request takes a long time to complete, the user may think the system isn't responding. If your program is a background task, these pauses will affect the performance of the current foreground application. To keep this to a minimum, avoid time-consuming asynchronous File Manager requests.
  • Chaining asynchronous File Manager calls will work on volumes controlled by synchronous drivers, but watch out: When the driver is synchronous, the stack frames from the system and your completion routines will keep building up on the current stack until the last asynchronous call in the chain completes, or until the stack overwrites the current heap. You'll need to break the asynchronous File Manager call chain every few completion routines. A simple way to do this is to start a Time Manager or VBL task from your File Manager call's completion routine, and let the task start the next asynchronous File Manager call in the chain.

File Sharing and AppleShare. Chained asynchronous File Manager calls can fail when either the Macintosh File Sharing or AppleShare 3.0 (not 3.0.1) file server is running. The file server software intercepts almost all calls made to the File Manager. Due to how the file server keeps track of what requests it has or hasn't seen, there are a few situations where the file server can do the wrong thing with chained asynchronous File Manager calls. To make sure the file server sees and handles all chained asynchronous File Manager calls correctly, use two parameter blocks for the chained calls and switch parameter blocks at every completion routine.


WE HATE IT WHEN YOU DON'T WRITE We welcome timely letters to the editors, especially from readers reacting to articles that we publish in develop. Letters should be addressed to Caroline Rose (or, if technical develop-related questions, to Dave Johnson) at Apple Computer, Inc., 20525 Mariani Avenue, M/S 303-4DP, Cupertino, CA 95014 (AppleLink CROSE or JOHNSON.DK). All letters should include your name and company name as well as your address and phone number. Letters may be excerpted or edited for clarity (or to make them say what we wish they did). *

SUBSCRIPTION INFORMATIONSubscriptions to develop are available through APDA (see inside back cover for APDA information), or you can use the subscription card in the back of this issue. Please address all subscription-related inquiries to develop, Apple Computer, Inc., P.O. Box 531, Mt. Morris, IL 61054 (or AppleLink DEV.SUBS). *

BACK ISSUES For information about back issues of develop and how to obtain them, see the last page of this issue. Back issues are also on the develop Bookmark CD and the Developer CD Series disc (Reference Library edition).*

Thanks to François Grieu and Lawrence D'Oliveiro for providing some of this information. *

 

Community Search:
MacTech Search:

Software Updates via MacUpdate

OnyX 3.2.0 - Maintenance and optimizatio...
OnyX is a multifunction utility that you can use to verify the startup disk and the structure of its system files, to run miscellaneous maintenance and cleaning tasks, to configure parameters in the... Read more
Macs Fan Control 1.4.4.0 - Monitor and c...
Macs Fan Control allows you to monitor and control almost any aspect of your computer's fans, with support for controlling fan speed, temperature sensors pane, menu-bar icon, and autostart with... Read more
calibre 2.69.0 - Complete e-book library...
Calibre is a complete e-book library manager. Organize your collection, convert your books to multiple formats, and sync with all of your devices. Let Calibre be your multi-tasking digital librarian... Read more
Evernote 6.9.1 - Create searchable notes...
Evernote allows you to easily capture information in any environment using whatever device or platform you find most convenient, and makes this information accessible and searchable at anytime, from... Read more
jAlbum Pro 13.5 - Organize your digital...
jAlbum Pro has all the features you love in jAlbum, but comes with a commercial license. You can create gorgeous custom photo galleries for the Web without writing a line of code! Beginner-friendly... Read more
jAlbum 13.5 - Create custom photo galler...
With jAlbum, you can create gorgeous custom photo galleries for the Web without writing a line of code! Beginner-friendly, with pro results - Simply drag and drop photos into groups, choose a design... Read more
Google Chrome 53.0.2785.143 - Modern and...
Google Chrome is a Web browser by Google, created to be a modern platform for Web pages and applications. It utilizes very fast loading of Web pages and has a V8 engine, which is a custom built... Read more
Chromium 53.0.2785.143 - Fast and stable...
Chromium is an open-source browser project that aims to build a safer, faster, and more stable way for all Internet users to experience the web. Version 53.0.2785.143: [Security Fix] High CVE-2016-... Read more
QuickBooks 2015 16.1.7.1524 R8 - Financi...
Save 20% on QuickBooks Pro for Mac today through this special discount link QuickBooks 2015 helps you manage your business easily and efficiently. Organize your finances all in one place, track... Read more
Sierra Cache Cleaner 11.0.1 - Clear cach...
Sierra Cache Cleaner is an award-winning general purpose tool for macOS X. SCC makes system maintenance simple with an easy point-and-click interface to many macOS X functions. Novice and expert... Read more

3 tips to aid your journey in Banner Sag...
Stoic Games brings us another viking epic in the guise of Banner Saga 2 this week. It’s a sweeping tale, richly animated and draped in melancholy and moments of beauty. The game’s been received as a much improved follow up to the first entry in the... | Read more »
Pumped BMX 3: Beginner tips and tricks
There’s a whole lot more to Pumped BMX 3 than meets the eye. Your goal is to perform a wide array of sweet flips and tricks, but that’s easier said than done. It takes well practiced timing and coordination, and the game doesn’t really explain that... | Read more »
Cybird’s latest release - BFB Champions...
Launched in the UK in early September, BFB Champions’ newest update is loaded with great new features, and looks set to outshine the original version by taking it out of soft launch and giving it a new lease of life. | Read more »
3 apps to boost your focus
As someone who works from home, my workspace is a minefield of distraction. Cats, tasty snacks, the wind blowing past my window, that cleaning that I suddenly can’t put off any longer. If I let distraction takes its course, I find that soon half... | Read more »
Pumped BMX 3 (Games)
Pumped BMX 3 1.0 Device: iOS Universal Category: Games Price: $3.99, Version: 1.0 (iTunes) Description: The final instalment of the smash hit #1 rated BMX game is here! Following on from the insane success of Pumped BMX 2, Pumped 3... | Read more »
4 games like Burly Men at Sea to inspire...
Burly Men at Sea is out today and it looks a treat. It tells the tale of three Scandinavian fishermen who leave the humdrum of their daily lives to go exploring. It’s a beautiful folksy story that unfurls as you interact with the environment... | Read more »
3 reasons you need to play Kingdom: New...
Developed by a tag team of indie developers - Thomas "Noio" van den Berg and Marco "Licorice" Bancale - Kingdom is a vibrant medieval fantasy adventure that casts players as a king or queen who must expand their empire by exploring the vasts lands... | Read more »
JoyCity have launched a brand new King o...
Great news for all of you Game of Dice fans out there - JoyCity have just released a brand new limited edition pack with a really cool twist. The premise of Game of Dice is fairly straightforward, asking you to roll dice to navigate your way around... | Read more »
Burly Men at Sea (Games)
Burly Men at Sea 1.0 Device: iOS Universal Category: Games Price: $4.99, Version: 1.0 (iTunes) Description: Burly Men at Sea is a folktale about a trio of large, bearded fishermen who step away from the ordinary to seek adventure. | Read more »
3 tips for catching the gnarliest waves...
Like a wave breaking on the shore, Tidal Rider swept its way onto the App Store charts this week settling firmly in the top 10. It’s a one-touch high score-chaser in which you pull surfing stunts while dodging seagulls and collecting coins. The... | Read more »

Price Scanner via MacPrices.net

CAZE Annouces New Zero 5 Case for Jet Black i...
Hong Kong basd CAZE has announced Zero 5 case for iPhone 7/ 7 Plus, one of the world’s thinnest clear hard cases, measuring just 0.5 millimeters. CAZE has been producing and improving the Zero 5... Read more
Nest Egg Inventory App for iOS Offers Conven...
Campbell, California based Winprogger LLC has announced the release and immediate availability of Nest Egg – Inventory 4.1.22, an important update to their easy-to-use, yet comprehensive inventory... Read more
Factor4, LLC Launches Apple iOS and Android G...
Factor4, LLC, which offers gift and loyalty services to the SMB marketplace, has released free mobile applications that enable merchants to process via all Apple and Android devices. The Apple and... Read more
15-inch Retina MacBook Pros on sale for $200...
B&H Photo has 15″ Retina Apple MacBook Pros on sale for $200 off MSRP. Shipping is free, and B&H charges NY tax only: - 15″ 2.2GHz Retina MacBook Pro: $1799 $200 off MSRP - 15″ 2.5GHz Retina... Read more
Apple refurbished iMacs available for up to $...
Apple has Certified Refurbished 2015 21″ & 27″ iMacs available for up to $350 off MSRP. Apple’s one-year warranty is standard, and shipping is free. The following models are available: - 21″ 3.... Read more
Check Apple prices on any device with the iTr...
MacPrices is proud to offer readers a free iOS app (iPhones, iPads, & iPod touch) and Android app (Google Play and Amazon App Store) called iTracx, which allows you to glance at today’s lowest... 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
Apple refurbished 2016 13-inch MacBook Airs a...
Apple has Certified Refurbished 2016 13″ MacBook Airs available starting at $849. An Apple one-year warranty is included with each MacBook, and shipping is free: - 2016 13″ 1.6GHz/8GB/128GB MacBook... Read more
1.4GHz Mac mini on sale for $449, save $50
Adorama has the 1.4GHz Mac mini on sale for $50 off MSRP including free shipping plus NY & NJ sales tax only: - 1.4GHz Mac mini (Apple sku# MGEM2LL/A): $449 $50 off MSRP To purchase a mini at... Read more
Apple refurbished 2015 13-inch MacBook Airs a...
Apple has Certified Refurbished 2015 13″ MacBook Airs available starting at $759. An Apple one-year warranty is included with each MacBook, and shipping is free: - 2015 13″ 1.6GHz/4GB/128GB MacBook... Read more

Jobs Board

Systems Architecture Prototyping - *Apple*...
Changing the world is all in a day's work at Apple . If you love innovation, here's your chance to make a career of it. You'll work hard. But the job comes with more Read more
*Apple* Retail - Multiple Positions- Akron,...
Job Description:SalesSpecialist - Retail Customer Service and SalesTransform Apple Store visitors into loyal Apple customers. When customers enter the store, Read more
Hardware Design Validation Engineer - *Apple...
Changing the world is all in a day's work at Apple . If you love innovation, here's your chance to make a career of it. You'll work hard. But the job comes with more Read more
Systems Architecture Prototyping - *Apple*...
Changing the world is all in a day's work at Apple . If you love innovation, here's your chance to make a career of it. You'll work hard. But the job comes with more Read more
*Apple* Retail - Multiple Positions- South B...
Job Description: Sales Specialist - Retail Customer Service and Sales Transform Apple Store visitors into loyal Apple customers. When customers enter the store, Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.