CP/M/CPM_CDROM.iso/cpm/z280/z280-j88.lbr/1Z280-DS.RMF

Text File | 1988-01-06 | 4KB | 69 lines

                 << DATESTAMPER and CRNCH23D >>

This file Z280-J88.MSG (the 'J88' indicating that it has been
created in January 1988, to distinguish it from countless other
files of a similar name) has been crunched with CRNCH23D, the
special DateStamper-supporting version of Steve Greenberg's
CRUNCH.COM.  I wrote it on January 1 and am crunching it and
sending Z280-J88.MZG out on the modem airwaves today, 1/3/88.
For those running DateStamper and downloading it to their own
computer, if they uncrunch it with UNCR23D it will automatically
retain the original (uncrunched) file's datestamp data from my
system.  'Automatically' here means here WITHOUT depending on the
crunching party (me) entering it manually in the "comment" field
or somewhere in the text.  For those who notice these things this
is not normally possible on either an uncompressed file or one
compressed with any other version of CRUNCH.  I don't think this
is normally appreciated and I think we should take more time to
understand what an advance this is.

As a hypothetical example, suppose we don't have DateStamper --
or that we do but we're not using versions 23D of CRUNCH/UNCRUNCH
-- or we're sending a file uncompressed via modem.  It is
December 23 and I have finally finished working on an article I
have been writing.  I am busy through the holidays and finally on
December 28 I have some time to send it up into the public domain
airwaves.  I crunch it and upload it to a BBS.  After the new
year you download it, say on Jan. 8 and uncrunch it and soon run
DateStamper's SDD (assuming you're running DS) on your disk.
Surprise: it says nothing about either December 23 OR December 28
but instead tells you that both the original and crunched file
were 'created' Jan. 8!  This is silly -- they certainly were not
created Jan. 8.  The uncompressed file was created (by me) on
December 23; you only received it on your system Jan. 8.

CRNCH23D and UNCR3D take care of this problem.  When you run
"UNCR23D Z280-J88.MZG" and do a directory with SDD the resultant
file Z280-J88.MSG will be seen with all its original and accurate
datestamp data AS I CREATED IT ON MY SYSTEM.  It is quite amazing
since normally a datestamp is wedded to the disk directory (CP/M
3.0 or Z80DOS) or the !!!TIME&.DAT file (non-CRNCH23D DateStamper
stamps) of the original computer or disk.  CRNCH23D stores in
encoded form the uncrunched file's datestamp at the very top (the
'header') of the crunched file.  This method of storing a
datestamp -- IN THE FILE ITSELF -- is absolutely unique in the
CP/M-compatible (and MS-DOS?) world.  These programs CRNCH23D and
UNCR23D actually are the only way we in the CP/M-compatible world
have of retaining a file's datestamp through a modem transfer.

The second half of the process I'm guessing at, but I imagine
that when UNCR23D comes around and uncrunches it that date
information from my system is un-encrypted and sent from the file
to embed itself in to the !!!TIME&.DAT file on YOUR directory.
Note that you will get the original creation date -- not even the
date of crunching -- from my file.  This is appropriate since you
thereby get a valid idea of when the file was truly created.
After uncrunching, SDD should tell you that Z280-J88.MSG was
created Jan. 1 and modified on Jan. 3, REGARDLESS OF WHEN YOU
DOWNLOADED THE LIBRARY.  Note also the irony: the process of
crunching is what gives us the possibility to preserve this
datestamp data; an uncrunched file cannot be dealt with in this
manner, and a downloaded uncrunched file will always appear on
your directory to have been 'created' on the day you downloaded
it!

Hats off and many thanks to Bridger Mitchell for this great and
significant advance in CP/M- compatible computing.

                                       - Rick Charnes