info-mac@uw-beaver (info-mac) (10/26/84)
From: Ed Pattermann <PATTERMANN@SUMEX-AIM.ARPA>
To respond to many requests for help and questions on how to download .RSRC
and .DL files (and just what are they?), Bill Croft and I have written a
document describing such. The document follows, and is also stored under
{SUMEX}<INFO-MAC>DOWNLOAD.DOC. I hope those who have questions find it useful.
-- Ed
-----------------
THIS FILE WILL EXPLAIN
o A Bit About Macintosh Files
o The Difference Between .Rsrc And .Dl Files
o How To Download .Rsrc And .Dl Files To A Macintosh
.... HOPE YOU FIND IT USEFUL
MACINTOSH FILES HAVE TWO 'FORKS'
Each file on your Mac consists of two parts: a data 'fork' and a
resource fork. Each fork is actually a complete, individual file. In
practice it turns out that most Mac files have information in only one
of the forks, the other fork is typically empty. (Sounds kind of
silly, huh)? Thus if a Mac file is called a 'resource file', it
generally has a resource fork but no data fork. Vice versa for a 'data
file'.
Examples of resource files are executable programs and fonts. Data
files would be ascii text files, pictures, etc. Resource files have an
additional characteristic: they have an internal structure consisting
of an index and one or more 'resource's, each with an 'id'. For
example, a font file has a separate id for each font type and size;
an executable program has an id for each overlay segment.
'*.RSRC' FILES
A Macintosh executable binary file (as generated by the Apple workshop
or by SUMacC or other compilers) is a resource file. On the
'development' host (Lisa, UNIX, [TOPS20 too]) the file will have the
filename suffix '.RSRC'. This is to distinguish which Mac fork the
file belongs in. These files are not printable, they contain only
8-bit binary data.
Sometimes you may see the file suffix '.DATA', this would represent
the contents of the data fork (data file).
'*.DL' FILES
8-bit binary data can't go thru the mail. 8-bit data also isn't very
user friendly on such systems as TOPS20; TOPS20 packs character
data by default in 7-bit bytes, which looses information in this case.
[SUMEX is a TOPS20 system].
For this reason, a simple format was invented, called 'fromhex' or
'.dl' (download) format. Each 8-bit binary byte in the .rsrc file is
represented as two printable ascii characters (hex nibbles) in the
.dl file. At the end of the .dl file is a checksum to guard against errors.
To translate between 8-bit binary and hex format there are two programs:
'fromhex' reads a hex file and writes a binary file;
'tohex' reads a binary file and writes a hex file. These programs are
FTPable from the [SUMEX]<info-mac> directory:
fromhexu.c UNIX C version (or Mac C with stdio)
fromhex.c Mac C version (SUMacC)
fromhex.p Mac compiled Pascal (Apple workshop compiler)
fromhex.rsrc executable version of fromhex.p
fromhex.dl .dl version of fromhex.rsrc
tohex.c UNIX C version
The fromhex programs assume that any mail headers have been removed
from the file. The UNIX version is a 'filter' [fromhex <x.dl >x.rsrc];
it reports whether the checksum was good or bad. The Mac version
reads a data file called 'C' and writes an executable resource file
called 'C prog'; it beeps if there was a checksum error.
FILES ARCHIVED ON SUMEX <INFO-MAC>
Since SUMEX is a TOPS20 (36-bit word) system, it has different file formats
for 7-bit ascii (printable) versus 8-bit (binary) files. .RSRC files
(and .DATA files) are stored in 8-bit mode. .DL files (and most other
files) are stored in the default 7-bit mode. This is important to know
if you are FTPing a file from SUMEX to a UNIX or most other systems.
When retrieving a file from SUMEX to a UNIX, check the suffix. If it
is .RSRC or .DATA, you must use the FTP command 'tenex' or 'type l 8'
before the transfer to get all 8 bits transfered correctly. If the
file has any other suffix, it is an ordinary text file and can be FTPed
with the default 'ascii' mode.
Whether a program is stored on SUMEX in .RSRC or .DL mode seems to
be a random function. Currently if you need the other format, you should
FTP it to your local site (usually a UNIX) and convert it there using
the fromhex/tohex programs listed above.
UNIX DOWNLOADING
First get the file into .rsrc form. This may require running fromhex.
Assume the resulting file is called handson.rsrc.
Run MacTerminal (version 1.1 is recommended). Ensure that the
MacTerminal configuration contains: 8 bits per char, parity none,
handshake none, xmodem transfer method, remote system macterminal, no
delays. The hardwire or modem connection to your UNIX must be capable
of passing all 8 bits transparently. If a terminal switcher, network
or 'smart modem' intercepts something, your transfer could freeze
midway.
Log into your UNIX and type 'macput -r handson'. This should start the
transfer automatically and show you a 'thermometer' indicating the
percentage of the transfer complete. After the transfer is complete
you can quit and double-click your new program to start it.
Macput / macget were written by Dave Johnson of Brown University and
are available for FTP from [SUMEX]<info-mac> {macget,macput}.{c,1}.
DOWNLOADING FROM OTHER HOSTS (E.G. TOPS20) WITHOUT MACPUT
Macput understands the same XMODEM protocol that MacTerminal uses. Macput
also knows a special Mac-only protocol used between two consenting
MacTerminals. The Mac-only protocol allows an entire Mac file, consisting
of data and resource forks, to be transfered.
There are other programs which speak XMODEM, for example the MODEM
program on TOPS20. However MODEM does not currently have a switch
to turn on the Mac-specific protocol. Consequently, MODEM can only
transfer a data fork to or from the Mac. There is no way, either on
MacTerminal or MODEM, to specify a resource fork transfer.
[We have heard rumors that BILLW@SRI is working on fixing MODEM.]
There is another possibility: KERMIT. If you have kermit running on
your host, and a Mac disk containing the kermit program, you should
be able to transfer resource and data files. Since the Mac kermit is
just stabilizing and is not yet in wide availability, we havent tried
this yet. Perhaps your hardest task will be to get the binary kermit
program onto your Mac disk. Sounds like a bootstrap problem...
For folks without macput, kermit, or anything, read on about .DL downloading.
DOWNLOADING .DL FILES
You need a Mac disk with the 'fromhex' program discussed above. This was
originally sent out with the early SUMacC distribution (before macput).
If you don't have it you might: (1) find a UNIX friend who can macput
it to your disk. (2) download (via lisaterminal 'receive to file')
fromhex.p to your Lisa and compile it. (3) download (via MacTerminal
'save lines off top') fromhex.c to your Mac and use a C compiler to
compile it. (4) translate fromhex to your favorite language;
mikes@cit-vax has a Forth version, does someone have a Basic version?
After you have fromhex and MacTerminal on your disk, login to your
host and ensure that the .dl file has no garbage or headers on the front
of it. Then using MODEM (on TOPS20) or 'save lines off top', transfer
the printable .dl file to your Mac disk as a file named 'C'. When
the transfer is complete, quit MacTerminal and run fromhex. This will
read 'C' and produce 'C prog'. Fromhex will beep if there was a checksum
error. After you have the finder again, rename 'C prog' to whatever
and double click it; your program should start.
Bill Croft and Ed Pattermann
SUMEX Computer Project
----------------------------
-------info-mac@uw-beaver.UUCP (11/02/84)
From: Bill Croft <croft@safe> Date: Mon, 29 Oct 84 12:45:10 PST From: Matthew J Weinstein <matt@UCLA-LOCUS.ARPA> Subject: Re: Help on downloading MACintosh files Why weren't DL files defined to use 6 bits per character? This would have yielded only 25% waste, instead of 50%. There are 64 printable characters in ASCII, I think. Also, the most brain-damaged machines I can think of, short of a 4004, have at least a 6-bit character set. Just curious. - Matt ---- The fromhex/tohex stuff was only intended as a primitive way to download programs in the early (June) version of our SUMacC cross development system. It was made to be as simple as possible. We never intended it as a universal mail-media for Mac programs. It just began to be used that way. Actually, as I understand it, the BINHEX format (used on Compuserve MAUG) is somewhat more general, in that it allows the data, resource, and 'finder info' (4 bytes each of type/owner) portions of a file to be represented as one hex collection of stuff. Again, though, it's hex instead of sixbit. Also, it only exists right now as a 500 line MS-Basic program. Fromhex.c is only 30 lines long. Frankly I store all this stuff in 8-bit '.rsrc' files on my UNIX. You could use UNIX 'uucp' 'uuencode' (a six bit format) if you want to mail these files most efficiently.