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Apple //e De-ARC
Version 1.1
8/23/88
The original ARC is Copyright (c) 1985 by Thom Henderson, System
Enhancements Associates.
The port to the Apple //GS (DEARC only) is Copyright (c) 1987 by Tim
Swihart, P.O. Box 26303, Fort Worth, TX 76121.
The port of De-ARC to the Apple //e is Copyright (c) 1988 by David R.
Larsen, P.O. Box 160313, Cupertino CA 95016, All Rights Reserved.
1. Introduction
ARC is an archiving utility first developed on the IBM PC. Versions
now exist for Amiga and Atari as well. Early versions simply packed
multiple related files into a single file for ease of storing and
manipulating. Later versions began to compress the files as well, to
reduce disk storage space and to reduce telecommunication time when
moving the files between machines. ARC is widely used in the IBM PC
world for source code and executables, and in the Amiga world for
picture files. ARC is frequently used as a method of compressing text
files on bulletin boards and Information Services, and are typically
stored under names such as "knr.arc".
Until recently, there was no way for Apple //'s to take advantage of
these text files. Then Tim Swihart ported the de-ARC code from the PC
version written by Thom Henderson and System Enhancement Associates to
the Apple 2 GS.
Dearc2e is a port of the 2GS version of the de-ARC code, to run on the
Apple //e.
This program only De-ARCs files. A future release may include the
capability to ARC as well.
Supported compression types are the "Packed", "Squeezed" (Huffman),
"crunched" (LZW) and "Crunched" (Dynamic LZW). A compression type
being used in some IBM PC implementations, "Squashed", is not
supported.
2. System Requirements
An Apple //e or //c with 128k, and ProDOS 8. An accelerator card is
recommended but not required. Dearc2e has only been tested on an
enhanced //2, but I know of no reason it should not work on unenhanced
//e's and //c's.
The contents of auxiliary memory, typically devoted to /ram, will be
deleted. If dearc2e thinks there is something in /ram, you will be
asked if this is acceptable. If it is not, dearc2e will exit.
3. How to use it
Dearc2e is a ProDOS 8 SYS file. It may be started from a shell or
from Applesoft using the - command. A list of available options will
be provided:
[L]ist contents of an archive
[E]xtract contents of an archive
[S]et name of archive to work with
[Q]uit
You may then enter one of the commands, either in upper case or lower
case.
3.1 List
For each file stored in the archive, the List command displays its
name, its size as stored in the archive and as it will be when
removed, and the method of compression used. File names may contain
illegal ProDOS characters; dearc2e will change any invalid characters
to periods, and leading numbers to 'z' when the file is extracted.
If the Set command has not yet been given, you will first be prompted
for the name of the archive file to use. Standard ProDOS path names
may be used. This will then Set that file for subsequent use.
3.2 Extract
The Extract command actually removes one or more files from the
archive. You are first prompted for the archive file name if it has
not yet been provided. The Extract command will put the de-ARCed files
into the same directory as the archive file.
You are then asked if you want to extract All, Some or None of the
files; if None, the extract command is cancelled and you are returned
to the initial command list. If you select Some, you are then asked
file by file if you want that file to be extracted or not. Enter y or
n, or to cancel extracting, enter a q.
While extracting a file, an approximate percent complete will be
displayed to show progress.
3.3 Set
As stated above, Set allows you to specify the name of the archive
file to use for subsequent operations. This allows you to de-ARC
several files without quitting and restarting. If you mistype the file
name at one of the other commands, use Set to change it.
3.4 Quit
Quit terminates the program.
3.5 A Potential Problem
When Dearc2e is run from BASIC.SYSTEM, typing in the name of the file
to de-arc without also entering its prefix may not work, even if the
file is in the current prefix. This is due to a bug in BASIC.SYSTEM.
If this happens, you'll get the message "Illegal arc file". Simply
enter the file name again using the full prefix. If you set the prefix
just before invoking Dearc2e, this problem does not seem to appear.
4. Changes from Previous Releases
Version 1.1 differs from 1.0 in the following ways:
* A problem that could cause a crash when exiting was fixed.
* The screen is now automatically initialized to 80 columns.
* If the requested file is not found or is not a valid ARC format
file, the program no longer exits after reporting the error.
* The performance of the screen updating has been improved somewhat.
5. Development Details (for those who care)
Dearc2e was developed on an enhanced Apple //e, under ProDOS 8 version
1.4, with the following additional hardware: 128k, 512k Ramfactor,
Transwarp Accelerator, Sider 10 Meg Hard disk.
The code is written in C, using Manx Aztec C65 for Apple //, version
3.2b.
Most of the code came from Tim Swihart's Apple 2 GS version. I
modified it to use auxiliary memory for the large memory buffers. I
also added a few more niceties, including displaying the percent done,
since the //e version is slower than the 2 GS version.
6. Conclusion and legal stuff
I have alluded above to possible future releases. These may or may not
occur, depending on a variety of things.
In the spirit of the original sources for this program, it is
considered Freeware. No payment is required, but if you find it
useful, I will gladly accept a registration fee of $10; for that you
will receive at least one additional upgrade, should there be one.
Please let me know what version you have when registering.
You may distribute this program provided that this document is
distributed with it. Copies of the program may not be sold for more
than $10. Dearc2e is supplied as-is and the author disclaims all
warranties, expressed or implied, including, without limitation, the
warranties of merchantability and the warranties of fitness for any
particular purpose.
David R. Larsen
GEnie address: D.LARSEN2
US Mail: P.O. Box 160313
Cupertino CA 95016-0313