TweetFollow Us on Twitter

Winter 92 - APPLE II Q & A

APPLE II Q & A

APPLE II Developer Technical Support

Q What's the best way to do text-only printing to a character device through GS/OS? 

A If you want to print text to a GS/OS character device, here's how you do it:

  1. Look at all the on-line devices to find which are character devices. You can tell when a device is a character device by examining bit 7 of the "characteristics" word returned by DInfo--the bit is set for block devices and clear for character devices. You don't have to hard-code a list of character device IDs.
  2. Present the user with a list of device names followed by their location and generic type in parentheses. You can adjust the names of device types to reflect your use. For example, ".RPM (AppleTalk printer, port 1)," ".DEV2 (serial modem, port 2)," or ".DEV3 (generic character device, slot 5)." You can use bit 3 of the slot returned by DInfo to know whether to return "slot" or "port," too.
  3. When the user selects a printing device, call Open on the device name (such as .RPM for an AppleTalk printer). Use Write to write the information, just as you would to a file; then call Close (you can call Flush if you like, but it shouldn't be necessary). That's all you need to do.

Remember not to embed ImageWriter or any other printer-specific codes in the output stream. With the exception of choosing a device and creating a file, this same code could be used to print to any  text printer or to another device such as a disk or modem. You might give users a "text printing preferences" dialog where they can enter some codes if they like, and you might have built-in sets for ImageWriters and other common printers, but don't make it too complicated. These instructions are very generic and will work well on any setup, not just an ImageWriter II connected through the serial port.

Q On a ROM 03 Apple II GS, I save and restore the mouse mode by getting it from ReadMouse, setting the mode to what I need, and restoring the value (with SetMouse) when done. This sometimes kills the mouse--I don't get any mouse movement until my program quits. Help! By the way, this isn't a problem on ROM 01 machines.  

A The ROM 03 mouse firmware doesn't behave as documented in two respects. First, it sometimes returns an illegal mouse mode value from ReadMouse. Specifically, there's garbage in the high nibble of the mouse mode byte. Second, SetMouse returns an error and takes no action when passed an invalid mode, even though the Apple IIGS Toolbox Reference  says it returns no errors. When you try to restore the invalid mode, nothing happens and the mouse stays in whatever mode you had it in--if it's not what the system needs, the mouse will appear "hung" until someone sets the mode to what the system does need.

You can work around this problem by masking off the high nibble of the mode result from ReadMouse (AND #$000F in 65816 assembly) before passing it to SetMouse. This problem is fixed in Apple IIGS system software version 6.0-- ReadMouse always returns a valid mode under 6.0.

Q When I call SFMultiGet2, I randomly get error $1705 (bad pathname descriptor in the reply record) even though that error doesn't mean anything for that call. Any ideas? 

A All versions of SFMultiGet2 before Apple II GS System 6.0 incorrectly look at two of the words in the reply record (offsets $0008 and $000E) to make sure they don't contain the value $0002. That value would be illegal in those positions--in any of the other  new Standard File calls. SFMultiGet2 doesn't use the same reply record, but pre-6.0 versions of Standard File accidentally check those fields anyway. Make sure the values in bytes that are past the beginning of the 6-byte reply record are not $0002. This is fixed in System 6.0.

Q Although my application fully supports GS/OS, the Finder uses slashes instead of colons in the pathnames in message #1. This means my application can't open any files that have slashes in the filename. 

A The Finder and its message-passing conventions were originally released before GS/OS was written. Applications depend on the slash (/) as the separator character to be able to parse these pathnames (for example, to find the filename to use in a document window title). If the separator character were to change, many older applications would break.

Finder version 6.0 may support an additional message containing a list of fully expanded GS/OS pathnames. These pathnames use colons as separators and aren't limited to 255 characters. See the Finder 6.0 documentation for details on using this message.

Q I've written a program that hangs inside Standard File under Apple II GS System 5.0.4, but works fine under development versions of 6.0. I'm not using any 6.0-specific features. What could be the problem? 

A Standard File before System 6.0 does not behave gracefully if called with both prefix 0 and prefix 8 empty. Try setting one of these prefixes to an existing directory and see if your problem vanishes.

Q I can't find the ProDOS partition on Volume IX or later of the Developer CD Series discs. What's happened? 

A Apple II information was duplicated on all Developer CDs from Volume III through Volume VIII because without the ProDOS partition, Apple II users couldn't see the information, and without the Apple II folder on the HFS partition, the information couldn't be shared on an AppleShare file server (or Macintosh System 7 File Sharing). Apple II GS System 6.0 includes an HFS (Macintosh) file system translator, which means that Apple II GS developers can access the information on the HFS partition, making the ProDOS partition unnecessary.

The Apple II information can be found on the HFS partition with the pathname Dev.CD Vol. IX:Development Platforms (Moof!):Apple II. Note that this means the Apple II folder can only be accessed from ProDOS 8 using AppleShare with long naming on--the path to the Apple II folder is not a legal ProDOS 8 pathname.

Q Apple II Applesoft's floating-point routine results are sometimes accurate to only two places. For example, the answer returned for PRINT 55555.099-55555.09 is 9.01031494 E-03. How can we get more accurate results? 

A The accuracy loss you're experiencing with the Applesoft floating-point routines is normal. If you convert a number such as 55555.099 to a base 2 floating-point number, you won't get an exact representation using Applesoft's floating-point routines or even 96-bit precision IEEE numerics. Because 9.01031494 E-03 is 0.0090103, you can see that you have accuracy out to three and a half decimal places. The solution is to determine the accuracy that you want and massage the result to give you that accuracy. Here's a sample program that shows common Applesoft rounding techniques:

1 REM Round to 3 decimal places of accuracy example
10 Input a
20 Input b
30 If a-b>1000 then 100: REM no 3-digit rounding of numbers >1000
40 Print "Standard Applesoft Non-accurate result:";a-b
50 Print "Truncated result:";
   INT((a-b)*1000)/1000 60 Print "Rounded result:";
   INT(((a-b)+.0001)*1000)/1000
70 Goto 10
100 Print "Result has 3 decimal accuracy already:";a-b
110 Goto 10

This is the only way that you can get Applesoft to clip the numbers, apart from using a separate floating-point engine. Alternatively, you can do your own conversion from Applesoft internal numeric format to a string in assembly language and have it simulate the above operation when converting the number.


Kudos to our readers who care enough to ask us terrific and well thought-out questions. The answers are supplied by our teams of technical gurus; our thanks to all. Special thanks to Matt Deatherage, Jim Luther, Dave Lyons, Jim Mensch, and Tim Swihart for the material in this Q & A column. *



Have more questions? Need more answers? Take a look at the Dev Tech Answers library on AppleLink (updated weekly) or at the Q & A stack on the Developer CD Series  disc.*

 
AAPL
$96.93
Apple Inc.
-0.26
MSFT
$44.54
Microsoft Corpora
-0.33
GOOG
$595.42
Google Inc.
-0.56

MacTech Search:
Community Search:

Software Updates via MacUpdate

Airfoil 4.8.7 - Send audio from any app...
Airfoil allows you to send any audio to AirPort Express units, Apple TVs, and even other Macs and PCs, all in sync! It's your audio - everywhere. With Airfoil you can take audio from any... Read more
Microsoft Remote Desktop 8.0.8 - Connect...
With Microsoft Remote Desktop, you can connect to a remote PC and your work resources from almost anywhere. Experience the power of Windows with RemoteFX in a Remote Desktop client designed to help... Read more
xACT 2.30 - Audio compression toolkit. (...
xACT stands for X Aaudio Compression Toolkit, an application that encodes and decodes FLAC, SHN, Monkey’s Audio, TTA, Wavpack, and Apple Lossless files. It also can encode these formats to MP3, AAC... Read more
Firefox 31.0 - Fast, safe Web browser. (...
Firefox for Mac offers a fast, safe Web browsing experience. Browse quickly, securely, and effortlessly. With its industry-leading features, Firefox is the choice of Web development professionals... Read more
Little Snitch 3.3.3 - Alerts you to outg...
Little Snitch gives you control over your private outgoing data. Track background activityAs soon as your computer connects to the Internet, applications often have permission to send any... Read more
Thunderbird 31.0 - Email client from Moz...
As of July 2012, Thunderbird has transitioned to a new governance model, with new features being developed by the broader free software and open source community, and security fixes and improvements... Read more
Together 3.2 - Store and organize all of...
Together helps you organize your Mac, giving you the ability to store, edit and preview your files in a single clean, uncluttered interface. Smart storage. With simple drag-and-drop functionality,... Read more
Cyberduck 4.5 - FTP and SFTP browser. (F...
Cyberduck is a robust FTP/FTP-TLS/SFTP browser for the Mac whose lack of visual clutter and cleverly intuitive features make it easy to use. Support for external editors and system technologies such... Read more
iExplorer 3.4 - View and transfer all th...
iExplorer is an iPhone browser for Mac lets you view the files on your iOS device. By using a drag and drop interface, you can quickly copy files and folders between your Mac and your iPhone or... Read more
Airmail 1.4 - Powerful, minimal email cl...
Airmail is a powerful, minimal mail client.It was designed to retain the same experience with a single or multiple accounts and provide a quick, modern and easy-to-use user experience. Airmail... Read more

Latest Forum Discussions

See All

More Paintings Have Been Added to Paint...
More Paintings Have Been Added to Paint it Back! Posted by Jessica Fisher on July 24th, 2014 [ permalink ] Universal App - Designed for iPhone and iPad | Read more »
The Order of Souls Review
The Order of Souls Review By Campbell Bird on July 24th, 2014 Our Rating: :: STORY GRINDUniversal App - Designed for iPhone and iPad The Order of Souls is a free-to-play, turn-based RPG with a genre-mixing art style, interesting... | Read more »
Revolution 60 Review
Revolution 60 Review By Jordan Minor on July 24th, 2014 Our Rating: :: LASS EFFECTUniversal App - Designed for iPhone and iPad Revolution 60 is a bold, cinematic action game with ambition to spare.   | Read more »
Matter (Photography)
Matter 1.0.1 Device: iOS Universal Category: Photography Price: $1.99, Version: 1.0.1 (iTunes) Description: Add stunning 3D effects to your photos with real-time shadows and reflections. Export your creations as photos or video loops... | Read more »
Fanatic Earth Review
Fanatic Earth Review By Brittany Vincent on July 24th, 2014 Our Rating: :: BY-THE-NUMBERSUniversal App - Designed for iPhone and iPad Kemco’s stable of mobile RPGs grows, but in Fanatic Earth’s situation it’s a case of quantity... | Read more »
Together for iOS (Productivity)
Together for iOS 1.0 Device: iOS Universal Category: Productivity Price: $9.99, Version: 1.0 (iTunes) Description: Together is an app for keeping things in one place. Notes, documents, images, movies, sounds, web pages and bookmarks... | Read more »
The Phantom PI Mission Apparition (Game...
The Phantom PI Mission Apparition 1.0 Device: iOS Universal Category: Games Price: $1.99, Version: 1.0 (iTunes) Description: ** Release sale! 50% off for a limited time! ** The Phantom PI Mission Apparition is a spooky, puzzly, rock’... | Read more »
The Great Prank War (Games)
The Great Prank War 1.0.0 Device: iOS Universal Category: Games Price: $2.99, Version: 1.0.0 (iTunes) Description: Help Mordecai, Rigby, Muscle Man and Skips take the park back from Gene and his goons with a plethora of prank-related... | Read more »
Teenage Mutant Ninja Turtles (Games)
Teenage Mutant Ninja Turtles 1.0.0 Device: iOS Universal Category: Games Price: $3.99, Version: 1.0.0 (iTunes) Description: Download the all new Teenage Mutant Ninja Turtles Official Movie Game! | Read more »
Dream Revenant (Games)
Dream Revenant 1.0 Device: iOS Universal Category: Games Price: $1.99, Version: 1.0 (iTunes) Description: EXCLUSIVE LAUNCH PRICE ! Dream Revenant is at $1.99 for a limited time ! | Read more »

Price Scanner via MacPrices.net

What Should Apple’s Next MacBook Priority Be;...
Stabley Times’ Phil Moore says that after expanding its iMac lineup with a new low end model, Apple’s next Mac hardware decision will be how it wants to approach expanding its MacBook lineup as well... Read more
ArtRage For iPhone Painting App Free During C...
ArtRage for iPhone is currently being offered for free (regularly $1.99) during Comic-Con San Diego #SDCC, July 24-27, in celebration of the upcoming ArtRage 4.5 and other 64-bit versions of the... Read more
With The Apple/IBM Alliance, Is The iPad Now...
Almost since the iPad was rolled out in 2010, and especially after Apple made a 128 GB storage configuration available in 2012, there’s been debate over whether the iPad is a serious tool for... Read more
MacBook Airs on sale starting at $799, free s...
B&H Photo has the new 2014 MacBook Airs on sale for up to $100 off MSRP for a limited time. Shipping is free, and B&H charges NY sales tax only. They also include free copies of Parallels... Read more
Apple 27″ Thunderbolt Display (refurbished) a...
The Apple Store has Apple Certified Refurbished 27″ Thunderbolt Displays available for $799 including free shipping. That’s $200 off the cost of new models. Read more
WaterField Designs Unveils Cycling Ride Pouch...
High end computer case and bag maker WaterField Designs of San Francisco now enters the cycling market with the introduction of the Cycling Ride Pouch – an upscale toolkit with a scratch-free iPhone... Read more
Kingston Digital Ships Large Capacity Near 1T...
Kingston Digital, Inc., the Flash memory affiliate of Kingston Technology Company, Inc.,has announced its latest addition to the SSDNow V300 series, the V310. The Kingston SSDNow V310 solid-state... Read more
Apple’s Fiscal Third Quarter Results; Record...
Apple has announced financial results for its fiscal 2014 third quarter ended June 28, 2014, racking up quarterly revenue of $37.4 billion and quarterly net profit of $7.7 billion, or $1.28 per... Read more
15-inch 2.0GHz MacBook Pro Retina on sale for...
B&H Photo has the 15″ 2.0GHz Retina MacBook Pro on sale for $1829 including free shipping plus NY sales tax only. Their price is $170 off MSRP. B&H will also include free copies of Parallels... Read more
Apple restocks refurbished Mac minis for up t...
The Apple Store has restocked Apple Certified Refurbished Mac minis for up to $150 off the cost of new models. Apple’s one-year warranty is included with each mini, and shipping is free: - 2.5GHz Mac... Read more

Jobs Board

Sr Software Lead Engineer, *Apple* Online S...
Sr Software Lead Engineer, Apple Online Store Publishing Systems Keywords: Company: Apple Job Code: E3PCAK8MgYYkw Location (City or ZIP): Santa Clara Status: Full Read more
Senior Interaction Designer, *Apple* Online...
**Job Summary** Apple is looking for a hands on Senior…will be a key player in designing for the Apple Online Store. The ideal designer will have a Read more
*Apple* Sales Chat Rep - Apple (United State...
…is looking for motivated, outgoing, and tech savvy individuals who want to offer Apple Customers an unparalleled customer experience over chat. At Apple , we believe Read more
Mac Expert - *Apple* Online Store Mexico -...
…MUST be fluent in English and Spanish to be considered for this position At Apple , we believe that hard work, a fun environment, creativity and innovation fuel the Read more
*Apple* Industrial Design CAD Sculptor - App...
**Job Summary** The Apple Industrial Design team is looking for a CAD sculptor/Digital 3D modeler to create high quality CAD models used in the industrial design process Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.