TweetFollow Us on Twitter

World CDEV
Volume Number:5
Issue Number:9
Column Tag:System Sleuthing

Related Info: Script Manager

World CDEV Investigated

By Martin Minow, Mike Carleton, Arlington, MA

Note: Source code files accompanying article are located on MacTech CD-ROM or source code disks.

Sleuthing the Map Cdev

[Martin Minow is a Principal Engineer at Digital Equipment Corporation. Originally a speech major (later a linguist), he decided he might need a “real” job someday, so he took the last programming course given for the Illiac I computer in 1962. When his graduate study grant ran out, he joined Digital Equipment Corporation in 1972, where he has held positions in software support and speech research and development, eventually working on the DECtalk speech synthesizer. He is currently a Principal Engineer in the mid-range system’s advanced development group. In his spare time, he runs marathons (slowly), and orienteers (even more slowly).

Mike Carleton received his BSEE in 1981. He first worked on special purpose compiler systems used to test the black boxes in fighter aircraft. After joining Digital Equipment Corporation in 1984 he supported the TOPS-10/20 COBOL compiler. Later he joined up as the system engineer for the VAX Supercomputer Gateway product and worked hand in hand with Cray Research engineers to make their two systems talk to each other. Currently, he is a Senior Software Engineer at Digital Equipment Corporation.]

System 6.0 includes an unexpected gimmick--a control panel program that displays a world map and allows you to select your location and time zone. The system is distributed with about 80 large cities already defined, and it is very easy to add your own location. However, there doesn’t appear to be any published way to extract the information for your own applications.

With a little poking around, we were able to decipher the internal information and think that other MacTutor readers might find it useful. By using the code in the following program, your phase of the moon program (or program to determine sunrise and sunset times) need not ask the user to specify the system’s location.

The program has only been tested on Mac SE’s and Mac II’s under System 6.0. At its heart is a subroutine to read data from the clock parameter ram.

The data is returned in three longwords with the following format (the actual numbers locate a suburb of Boston) found in figure 1.

Figure 1.

Latitude and longitude are stored as a fraction of the circle. You can think of latitude and longitude either as signed quantities ranging from -.5 to +.5, or as unsigned quantities ranging from 0 to 1. The right method depends on your program’s needs. For example, since people don’t think of Boston (71°05' West) as 288°55' East, a program that displays the location would probably treat the numbers as signed, as shown in the example program.

Time is stored as the number of seconds offset from UTC (GMT) in the low three bytes of the third longword. The high byte is zero. When the 24-bit value is sign-extended, it will be positive for offsets East of UTC, and negative for Western offsets.

Sleuthing the Parameter RAM

The parameter RAM is a block of memory in the clock chip that is kept alive by a battery when the computer is turned off. It was included in the Macintosh to store a small amount of environmental information that should not change when the system is booted from a different floppy. The MAP CDEV data is stored here because Apple wanted your Mac to know that it is located in Boston even if it was booted from a disk created in Cupertino.

The classic Macintosh has 20 bytes of parameter memory. The contents are copied to low memory when the system is booted and you should access it by referencing the SysParam block as discussed in Inside Macintosh, volume II, chapter 13. When Apple introduced the Mac SE and Mac II, they used a clock chip with 256 bytes of memory. Since only the 20 bytes of the classic Mac are copied to system memory, we had to find a way to access the rest of the information.

The read_param_ram() function below is the C-language interface to the undocumented _ReadXPRam trap that we found tucked away in the 256 KByte ROM. This routine can read any part (or all) of the 256 byte parameter RAM. It takes three parameters: a pointer to a buffer, an offset from the start of the parameter ram, and a count of bytes to copy to your program’s buffer. It returns an OSErr code which read_param_ram() then returns to your program.

Finally, we would remind you that you shouldn’t assume that Apple will keep this information in the same place or format in future system releases.

In a recently-published document, Apple described ScriptManager 2.0 which contains support routines to allow reading and writing the Map information. As we show in the article, the information is stored in three longwords (Fract format) with the following format:

/* 1 */
 
struct MachineLocation {
 Fract latitude;
 Fract longitude;
 union {
 char dlsDelta; 
 /* Signed byte: daylight savings time delta */
 long gmtDelta;
 } gmtFlags;
 };
 

The ScriptManager defines two functions to read and write the Map data:

  pascal void ReadLocation(MachineLocation *loc);
  pascal void WriteLocation(const MachineLocation *loc);

(“const” is a keyword that was added to the Draft Ansi C Standard: it indicates that the parameter will not be changed by the function. You can omit it without harm.)

Latitude and longitude are stored as fractions of a great circle: see our code for details. The low-order three bytes of the third word (gmtFlags.gmtDelta & 0x00FFFFFF) contain the number of seconds the timezone is East of the prime meridian. Note that the high byte must be masked off and the high-bit propogated to get the timezone offset: this is shown in our program. The high byte is marked “reserved” but seems to be a repository for a Daylight Savings Time offset.

I don’t know when the ReadLocation (and WriteLocation) functions will be available: they are not present in the current release of Think C. Until that time, our sample program should be usable, but the cautious program will switch to an approved interface as soon as possible.

/*
 * This is a simple program to demonstrate
 * extracting information from the Macintosh
 * parameter RAM and displaying the current
 * latitude, longitude, and time-zone offset.
 * Note that the format and manner of storage
 * of this data have not been published by
 * Apple.
 * This program is copyright © 1988, 1989
 * by MacTutor magazine.  You may incorpor-
 * ate portions of this program in your
 * applications without restriction.
 * Compile using Think C, V3.0.
 *
 * Written by Martin Minow and Mike Carleton
 */

#include<stdio.h>

/*
 * Define the “Read parameter ram” trap and
 * the offset in the parameter ram where the
 * map is stored.  This information doesn’t
 * seem to be written down anywhere.
 */
#define _ReadXPRam 0xA051
#define Map_Offset 0xE4 /* Ram offset*/

/*
 * This structure defines the location
 * currently set by the Map Cdev.
 * Latitude and longitude are long integers
 * specifying the fraction of the circle:
 *      1 degree East == 0x000308B9
 *      1 degree West == 0xFFFCF747
 * All values are possible for longitude,
 * while latitude is constrained to ± 90°.
 * Only the low-order three bytes of timezone
 * are used.  The value is the number of
 * seconds offset from UTC, East is positive,
 * West negative.
 */
#ifdef Use_Script_Manager
#include <ScriptMgr.h>

typedef struct {
 Fract  latitude;
 Fract  longitude;
 union {
 char dlsDelta;
 long gmtDelta;
 } gmtFlags;
} MachineLocation;

MachineLocation  info;
pascal void ReadLocation(MachineLocation *);
#else
typedef struct {
 long latitude;
 long longitude;
 long timezone;
} MapDatum;
 
MapDatuminfo;  
#endif

void    main(void);
void    dms(long, char *, char *);
void    hms(long, char *);
OSErr   read_param_ram(void *, int, int);

void    printf(char *, ...);
intfgetc(FILE *);

void
main()
{
 OSErr  status;
 /*
  * This is a test for divide rounding.
  * It should yield 180°00’00" W.
  */
 dms(0x80000000L, “Test”, “EW”);
 /*
  * Loop through here until the user types ‘q’ -- this lets you run the 
Map Cdev at the same time to see how location and timezone changes affect 
the data.
  */
 do {

#ifdef Use_Script_Manager
 ReadLocation(&info);
 dms(info.latitude, “Latitude”, “NS”);
 dms(info.longitude,”Longitude”, “EW”);
 hms(info.gmtFlags.gmtDelta, “Zone”);
#else
 status = read_param_ram(&info,
 Map_Offset, sizeof (MapDatum));
 if (status != noErr)
 printf(“Error %d\n”, status);
 dms(info.latitude, “Latitude”, “NS”);
 dms(info.longitude,”Longitude”, “EW”);
 hms(info.timezone, “Zone”);
#endif
 } while (getchar() != ‘q’);
}

/*
 * Convert to degrees/minutes/seconds.
 */
void
dms(raw_value, what, zone)
long    raw_value;
char    *what;
char    *zone;
{
 register long value;
 register long degree, minute, second;
 int    west;

 static longone_degree = (0x80000000L / 180L);
 static longone_minute = (0x80000000L / (180L * 60L));
 static longone_second = (0x80000000L / (180L * 60L * 60L));

 value = raw_value;
 degree = value / one_degree;
 value -= (degree * one_degree);
 minute = value / one_minute;
 value -= (minute * one_minute);
 second = value / one_second;
 if ((west = (raw_value < 0))) {
 degree = (-degree);
 minute = (-minute);
 second = (-second);
 } 
 printf(“%08lx: %3ld°%02ld’%02ld\” %c %s\n”,
 raw_value, degree, minute, second, zone[west], what);
}

/*
 * Convert time to hours:minutes:seconds.
 */
void
hms(timezone, what)
long    timezone;
char    *what;
{
 register long value;
 register long hour, minute, second;
 int    west;

 static longone_hour = (60L * 60L);
 static longone_minute  = (60L);

 if (timezone & 0xFF000000) {
 printf(“timezone high byte %08lx\n”,
 timezone);
 timezone &= 0x00FFFFFF;
 }
 /*
  * Propogate sign bit from bit 23 to bit 31 if West of UTC.
  */
 if ((timezone & 0x00800000) != 0)
 timezone |= 0xFF000000;  
 value   = timezone;
 hour  = value / one_hour;
 value  -= (hour * one_hour);
 minute  = value / one_minute;
 value  -= (minute * one_minute);
 second  = value;
 if ((west = (timezone < 0))) {
 hour = (-hour);
 minute = (-minute);
 second = (-second);
 } 
 printf(“%08lx: %3ld.%02ld.%02ld  %c %s\n”,
 timezone, hour, minute, second, “EW”[west], what);
}

/*
 * Read data from the clock parameter ram.  The start parameter specifies 
the offset within the parameter ram where the read is to start. The count 
parameter specifies the number of bytes to read.
 */
OSErr
read_param_ram(address, start, count)
void    *address;/* Result loc*/
intstart; /* Ram start  */
intcount; /* Read size  */
{
 /*
  * Put the count into the high word of D0, the pRRAM start address into 
the low word of D0, the Macintosh memory address in A0, and trap to ROM. 
 _ReadXPRam returns noErr on success and prInitErr on failure.
  */
 asm {
 move.w count,D0
 swap   D0
 move.w start,D0
 movea.laddress,A0
 dc.w   _ReadXPRam
 return
 }
}

 
AAPL
$524.94
Apple Inc.
+5.93
MSFT
$40.01
Microsoft Corpora
-0.39
GOOG
$536.10
Google Inc.
-20.44

MacTech Search:
Community Search:

Software Updates via MacUpdate

Tweetbot 1.5.1 - Popular iOS twitter cli...
Tweetbot is a full-featured OS X Twitter client with a lot of personality. Whether it's the meticulously-crafted interface, sounds and animation, or features like multiple timelines and column views... Read more
Mac DVDRipper Pro 4.1.7 - Copy, backup,...
Mac DVDRipper Pro is the DVD backup solution that lets you protect your DVDs from scratches, save your batteries by reading your movies from your hard disk, manage your collection with just a few... Read more
PDFpenPro 6.2 - Advanced PDF toolkit for...
PDFpenPro allows users to edit PDF's easily. Add text, images and signatures. Fill out PDF forms. Merge or split PDF documents. Reorder and delete pages. Even correct text and edit graphics! Create... Read more
PDFpen 6.2 - Edit and annotate PDFs with...
PDFpen allows users to easily edit PDF's. Add text, images and signatures. Fill out PDF forms. Merge or split PDF documents. Reorder and delete pages. Even correct text and edit graphics! Features... Read more
Monolingual 1.5.9 - Remove unwanted OS X...
Monolingual is a program for removing unnecesary language resources from OS X, in order to reclaim several hundred megabytes of disk space. It requires a 64-bit capable Intel-based Mac and at least... 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
Starcraft II: Wings of Liberty 1.1.1.180...
Download the patch by launching the Starcraft II game and downloading it through the Battle.net connection within the app. Starcraft II: Wings of Liberty is a strategy game played in real-time. You... Read more
Sibelius 7.5.0 - Music notation solution...
Sibelius is the world's best-selling music notation software for Mac. It is as intuitive to use as a pen, yet so powerful that it does most things in less than the blink of an eye. The demo includes... Read more
Typinator 5.9 - Speedy and reliable text...
Typinator turbo-charges your typing productivity. Type a little. Typinator does the rest. We've all faced projects that require repetitive typing tasks. With Typinator, you can store commonly used... Read more
MYStuff Pro 2.0.16 - Create inventories...
MYStuff Pro is the most flexible way to create detail-rich inventories for your home or small business. Add items to MYStuff by dragging and dropping existing information, uploading new images, or... Read more

Latest Forum Discussions

See All

Have a Special Dead Trigger 2 Easter Bas...
Have a Special Dead Trigger 2 Easter Basket Full of Goodies, Courtesy of Madfinger Games Posted by Rob Rich on April 18th, 2014 [ permalink ] Dead Trigger 2 | Read more »
Zynga Launches Brand New Farmville Exper...
Zynga Launches Brand New Farmville Experience with Farmville 2: Country Escape Posted by Tre Lawrence on April 18th, 2014 [ permalink ] | Read more »
David. Review
David. Review By Cata Modorcea on April 18th, 2014 Our Rating: :: MINIMALISTIC IN A DIFFERENT WAYUniversal App - Designed for iPhone and iPad David is a minimalistic game wrapped inside of a soothing atmosphere in which the hero... | Read more »
Eyefi Unveils New Eyefi Cloud Service Th...
Eyefi Unveils New Eyefi Cloud Service That Allows Users to Share Media Across Personal Devices Posted by Tre Lawrence on April 18th, 2014 [ permalink ] | Read more »
Tales from the Dragon Mountain: The Lair...
Tales from the Dragon Mountain: The Lair Review By Jennifer Allen on April 18th, 2014 Our Rating: :: STEADY ADVENTURINGiPad Only App - Designed for the iPad Treading a safe path, Tales from the Dragon Mountain: The Lair is a... | Read more »
Yahoo Updates Flickr App with Advanced E...
Yahoo Updates Flickr App with Advanced Editing Features and More Posted by Tre Lawrence on April 18th, 2014 [ permalink ] | Read more »
My Incredible Body - A Kid's App to...
My Incredible Body - A Kid's App to Learn about the Human Body 1.1.00 Device: iOS Universal Category: Education Price: $2.99, Version: 1.1.00 (iTunes) Description: Wouldn’t it be cool to look inside yourself and see what was going on... | Read more »
Trials Frontier Review
Trials Frontier Review By Carter Dotson on April 18th, 2014 Our Rating: :: A ROUGH LANDINGUniversal App - Designed for iPhone and iPad Trials Frontier finally brings the famed stunt racing franchise to mobile, but how much does its... | Read more »
Evernote Business Notebook by Moleskin I...
Evernote Business Notebook by Moleskin Introduced – Support Available in Evernote for iOS Posted by Tre Lawrence on April 18th, 2014 [ permalink ] | Read more »
Sparkle Unleashed Review
Sparkle Unleashed Review By Jennifer Allen on April 18th, 2014 Our Rating: :: CLASSY MARBLE FLINGINGUniversal App - Designed for iPhone and iPad It’s a concept we’ve seen before, but Sparkle Unleashed is a solidly enjoyable orb... | Read more »

Price Scanner via MacPrices.net

iMacs on sale for up to $160 off MSRP this we...
Best Buy has iMacs on sale for up to $160 off MSRP for a limited time. Choose free home shipping or free instant local store pickup (if available). Prices are valid for online orders only, in-store... Read more
iPad Airs on sale this weekend for up to $100...
Best Buy has WiFi iPad Airs on sale for $50 off MSRP and WiFi + Cellular iPad Airs on sale for $100 off MSRP on their online store for a limited time, with prices now starting at $449. Choose free... Read more
Apple restocks refurbished Mac minis starting...
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
Hyundai Brings Apple CarPlay To The 2015 Sona...
Hyundai Motor America has announced it will bring Apple CarPlay functionality to the 2015 Sonata. CarPlay is pitched as a smarter, safer and easier way to use iPhone in the car and gives iPhone users... Read more
Updated iPads Coming Sooner Than We Had Thoug...
MacRumors, cites KGI securities analyst Ming Chi Kuo, well-respected as an Apple product prognisticator, saying that Apple will introduce an upgraded iPad Air and iPad mini in 2014/Q3, meaning the... Read more
Toshiba Unveils New High And Low End Laptop M...
Toshiba has announced new laptop models covering both the high-end and low-end of the notebook computer spectrum. Toshiba 4K Ultra HD Laptop Toshiba’s new Satellite P55t features one of the world’s... Read more
Save up to $270 with Apple refurbished 13-inc...
The Apple Store has Apple Certified Refurbished October 2013 13″ Retina MacBook Pros available starting at $1099, with models up to $270 off MSRP. Apple’s one-year warranty is standard, and shipping... Read more
Apple now offering refurbished iPad mini with...
The Apple Store has Certified Refurbished 2nd generation iPad minis with Retina Displays now available starting at $339. Apple’s one-year warranty is included with each model, and shipping is free.... Read more
Microsoft Blinks – Drops Microsoft Office 365...
Microsoft has dropped the annual subscription fee for Microsoft Office 365 Personal – which is needed in order to create and edit documents in Microsoft Office for iPad. However, Apple’s iOS and OS X... Read more
New AVG Vault Apps for iOS and Android Help K...
AVG Technologies N.V. an online security company for 177 million active users, has announced the launch of its latest mobile application, AVG Vault. The free app introduces an innovative user... 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
*Apple* Retail - Manager - Holyoke - Apple I...
Job Summary Keeping an Apple Store thriving requires a diverse set of leadership skills, and as a Manager, you’re a master of them all. In the store’s fast-paced, Read more
*Apple* Retail - Manager - Apple (United Sta...
Job SummaryKeeping an Apple Store thriving requires a diverse set of leadership skills, and as a Manager, you're a master of them all. In the store's fast-paced, dynamic Read more
*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
*Apple* Retail - Market Leader - Cincinnati...
…challenges of developing individuals, building teams, and affecting growth across Apple Stores. You demonstrate successful leadership ability - focusing on excellence Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.