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is now possible to override ARC's choice of the compressor,
and crunch everything in only one pass! Although this does
not necessarily ensure the most efficient use of disk space,
significant time savings can be achieved with only a small
sacrifice in storage.
In general ARC makes two passes through each source
file. On the first pass ARC counts the number of bytes in
the file and calculates a two byte checksum for each file
being archived. The checksum is stored in the archive and is
later used to verify the file's integrity. ARC also prepares
a frequency distribution of the bytes used in the file and
uses it to generate the Huffman codes. It then calculates
what the resultant length would be using each of the three
storage methods. (store, squeeze, squash, crunch, or pack)
Pass two then writes the file to the archive using the most
efficient of the five methods available.
ARC VERSION 2.20 PAGE - 10
In order to achieve some of the flexibility and ease of
use of the MS-DOS version we had to do something about
Commodore DOS. After all isn't:
del a:scrapfile1 c:scrapfile2 <return>
a heck of a lot easier than:
open 15,8,15
print#15,"s0:scrapfile1"
close 15
open 15,9,15
print#15,"s0:scrapfile2"
close 15
or what about:
move a:arc.exe b:arc.asm c:usq f:
That would take some doing! And yet it's the type of
thing you want to do quite easily when you're manipulating
your disk library.
In general drive letters are both easier and more
precise than drive numbers. If you're familiar with MS-DOS
or CP/M you probably prefer drive letters. If not, they may
take some getting used to. What we've done is assigned each
drive a letter according to the table below:
drive letter device number drive
------------ ------------- -----
a 8 0
b 8 1
c 9 0
d 9 1
e 10 0
f 10 1
g 11 0
h 11 1
Thus if you want a program on drive 1 of unit 10, you
can do any one of the following:
dload "program",d1 on u10 (basic 4.0)
load "1:program",10 (basic 2.0)
or
load "f:program" (with ARC)
ARC VERSION 2.20 PAGE - 11
If you want to load and run the program just type:
f:program <return>
ARC will load it and run it (or SYS to it if its
machine language)
In any case we felt that drive letters were
sufficiently useful that they would be worth the bother of
getting used to. If you're still not convinced think about
this example after you've read on.
arc/c d:arcfile a:asm.?? b:ed.?? c:*
We think you'll grow to appreciate the environment in
which ARC is available. Most of the commands that you will
often require to view directories, move files about, delete
files, rename files, or edit simple text files are at your
disposal. Future versions of ARC will have even more
commands. We felt that this is the environment in which ARC