Apr 86 Letters
Volume Number: 2
Issue Number: 4
Column Tag: Letters
Stolen From a Mac?
Erik Westra
Wellington, New Zealand
Your magazine is absolutely fantastic. I find that I can use something from every
artical, even though I work mostly in assembler. I hope that the "Electrical Mac
column continues; it's got just the type of info that you can't normally get hold of.
Here's something you might be interested in. While I was poking about in the
Mac's ROM, I took a look at the bit of code Steve Jasik mentioned on page 48 of your May
1985 issue. Steve said that the code blasts 32 long words into RAM and then hangs. This
is the code he was talking about (on a 512K Mac):
40AD30: LEA $40AD40,A0
MOVEQ #$18,D1
40AD36: MOVE.L (40)+,(A1)
ADDA.W D0,A1
DBRA D1,$40AD36
BRA *-02
Looking at this, I thought that this might be the code that displays the "sad
Macintosh" icon on the screen if the system bombs while booting. I displayed the 32 long
words at $40AD40 as an icon using a program I'd writen in Kriya's NEON language, and
look what I found (displayed at twice it's size):
Maybe the code is called by the RAM based operating system if it finds it's using
funny hardware (eg, in a Mac lookalike).
[Our Forth editor, Jörg Langowski, recently paid us a visit here in Placentia
while visiting from France, and I showed him Mr. Westra's letter. He was most
intrigued and promtly wrote this little stolen icon finder program in Mach 1, the
subject of his Threaded Code column this month. The icon is shown at twice it's normal
size by this program. Note that the location of this code is different in the new ROMS! A
sincere thank you Erik, for sharing this with your US friends. To my knowledge, this
has never been revealed! -Ed.]
( demo to get the stolen Apple icon out of the ROM )
( c ) ( J. Langowski 1986 for MacTutor )
( start address of the icon is at $40E132, on a Mac Plus)
( and at $40AD40 on a 512K Mac, found with NOSY 2.0)
hex
variable icon variable icnrect 4 vallot
40e132 icon !
00800080 icnrect ! 00c000c0 icnrect 4 + ! ( use double size )
: stolen icnrect icon call ploticon ;
( don't know why to use pointer instead of handle for ICON )
Feature Articles?
Paul Devey
Ottawa, Ontario
Mactutor is the best Journal I have seen anywhere for any price. I have waited
for years for a journal of your calibur. Please sign me up for a one year subscription
as well as all of the back issues. How about sometimes having a feature section or
feature issues on different topics such as graphics, sound, I/O etc. Keep up the great
work. The only place you should be able to find PHLUFF is between your toes. [This
month we feature desk accessories! -Ed.]
Abstract Wanted
William T. Cox
Madison, Wi.
Have you considered offering a subscription to source disks? I have no idea what
your demand is, but ( based on the last year) I believe that many people would be
intersted. Have you considered offering an index/abstract list for volume 1? A
Microsoft File data disk would be a useful offering. A brief abstract or keyord list could
be included with each article record. Thanks for a fine magazine! [Maybe the folks at
MacBriefs would make us one. -Ed]
Likes Fortran
John Fineout
Duncanville, Tx
Enclosed is my payment for 1986 MacTutor subscription. I depend on your
publication heavily to learn insights into programing the Macintosh. I am using Mac
Fortran 2.1 forom Microsoft and Macintosh Pascal. I have missed the articles on
Fortran in the alast few issues. I have ported several progams from an DEC VAX
11/750 over to the Macintosh with very little problem. I am interested to learn more
on how to create a Macintosh environment for input and output for such routines. Other
unknowns are how to make use of the keypad and detect tab and enter as a line
terminator.
The following Mac Fortran program can be used in substitution for the VAX
Fortran time and date system call. It can be made into a subroutine that returns the 23
character time and date sring similar to the VAX. [Note: code below is re-typed from a
letter, not pasted from source code as we normally do, so beware. -Ed.]
Program Time_Date
Character Months(12)*3,APM*3,datetime*23
Integer Seconds,MM,DD,YY,L,M
Real Hours
Data Months/'JAN','FEB','MAR','APR','MAY','JUN',
2 'JUL','AUG', 'SEP',''OCT','NOV','DEC'/
Call Time(Seconds)
Hours = Seconds/86400.0*24.0
L = AINT(Hours)
Mins = (Hours - L)* 60.0
if (L .gt. 12) then
APM = ' pm'
L = L - 12
Else
APM = ' am'
End if
Call Date(MM,DD,YY)
Write(datetime,fmt='I2,A,I2.2,A3,
2 a6,I2,a,A3,a,I2') L,char(58),Mins,APM,
2 ' Date ',DD,char(45), Months(MM),char(45),YY
Write (9,100)datetime
100 Format ('Time is now ',a23)
pause
stop
end
Maybe this will be helpful to someone. Please deep the Fortran articles coming.
[What would be the most help is to convince Microsoft to support and upgrade Fortran
to run under HFS on the Mac Plus before 1988, and to make their linker more MDS
compatible and bug free. A decent Mac interface would be nice also. And don't forget to
mention finishing the parameter glue file support and documentation! -Ed.]
Notes on Basic
Gary Voth
Ontario, Ca
I want to say that I enjy Dave Kelly's fine columns on BASIC programming.
BASIC is a favorite language of mine, despite its limitations. I love the interactive
pampering that only an interpreted language can give.
However, I spotted an error or two in the January article on using scroll bars
from BASIC. I'd like to share the corrections with your readers.
On page 25 the author notes a problem using the BASIC function DEFINT a-z with
library calls. To prevent errors from occurring when library routines care called, he
recommends defining integer arguments individually (by using the % sign) instead of
using the DEFINT statement. Actually, this does prevent the errors, but only by
accident!
The reason that calling a bibrary routine creates an error after a DEFINT
statement has to do with the way the routines are accessed by BASIC. When a
programmer invokes a library routine, such a
CALL DisposeScroll(ScrID%)
BASIC actually creates a data structure in memory that contains the routine's
object code and (in our example) assigns the starting address the variable name
"DisposeScroll." Since BASIC's interger data type is 16 bits long, and Macintosh
memory locations require at least 24 bits to represent, an error is generated if the
variable "DisposeScroll" is defined as an interger (as would be the case after a DEFINT
statement)!
It is easy to work around this limitation, however, by designating our llibrary
routine names as single-precision (32 bit) variables using the ! sign. This is done in
the form below:
DEFINT a-z
Call DisposeScroll!(scrID)
Alternatively, you can use the form:
DEFINT a-z
DisposeScroll! ScrID
Note that this is essentially the same thing as calling an assembly language
routine that has been appended to BASIC the old fashioned way-by POKE-ing it into an
array. The array's starting address, as returned by the VARPTR function, can never be
forced into an integer:
DEFINT a-z
...
DisposeScroll!=VARPTR(AsmArray(0)
CALL DisposeScroll!(ScrID)
One more note: In the question and answer section the author discusses ways to
clear parts of the screen individually without using the CLS function. (By "screen" we
of course mean window.) One simple way of doing this that wasn't mentioned is to
"paint" with white. Use the Quickdraw call FILLRECT or the BASIC LINE statement to
draw a rectangle of white pixels over the section of the window that neds to be erased.
For example:
Black% = 33
White% =30
...
LINE(50,50)-(100,100),White%,bf
will erase a section of the current output window 50 pixels square. Of course,
the current penmode shold be the default COPY mode. If it has been changed the
programmer should restore it with a CALL PENMODE(8) statement.
HFS and Dollars & $ense
Terry A. Ward
Cedar Falls, La
I read with interest the status of commecial software with the HFS file system
(vol.2 #1). I noticed that Dollars & $ense is noted as bombing with an insufficient
memory message. A quick fix that has worked for me is to reduce the number of desk
accessories in the system. By reducing the size of desk accessories from 22,730 bytes
to 12,926 I am able to use the product with no problems.
Keep up the great work with MacTutor!
The Max Board!
Mike Carlton
Berkeley, Ca
In the Dec. 1985 issue you have included one of my posts on the MouseHole,
concerning the MacMemory board. I would like to make a few corrections now that
some new information has come to light. I spoke to some of the MacMemory people at
the MacWorld conventionin San Francisco and the told me that the TheMax is NOT
compatible with the new ROMs from apple. However, they want to be fair to their
customers so they are offering an upgrade, at their cost, to TheMax2. This new board
comes; with 2 meg. of RAM and sockets for expansion to 4 meg! All you ned to do is plug
in 16 1 meg. chips and you have a 4 meg. Mac. The new board is compatible with the
new ROMs; however, if you use the new ROMs, you lose the non-volitable RAM disk.
Anyone with TheMax should contact their dealer. MacMemory is selling the
boards to the dealers at cost and asking the dealers to do the upgrade (just a board swap)
at no profit. They said prices shold be around $150, but this wasn't finalized.
Friend of MacTutor
Doyle B. Myers
Seattle, Wa
I heard about your "setback" - the loss of your equipment and records from Steve
Brecher, my Compu Serve buddy. He suggested that subscribing to MacTutor would be a
nice way to help out, and you've got such an impressive reputation with all my fellow
developers that I have no problems at all with that. Good luck and keep up the good
work! [Thank you very much and to all of our friends and supporters who have
expressed their appreciation for our continued publication. -Ed.]
Renewal to ease the pain
Rod Paine
Purcellville, Va
Sorry to learn of your robbery at MacTutor, I hope you're able to put things back
together without too much of a loss being sustained.
I know that every little bit can help right now, so I've enclosed a subscription
renewal... I think mine is up about August, but in any ccase please add this onto it.
While we only met briefly at the Boston Mac Expo and we'd never be able to pick
each other out in a crowd, what you are poviding the readers of MacTutor does maake
you stand out... and I'm pleased to be a part of the readership and what MacTutor stands
for. [Spoken like a true old-timer! Thanks very much. -Ed.]
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