ARJ

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== Discussion ==
 
== Discussion ==
 
ARJ was one of the leading compression tools during the 1990s. While it was a bit slower than [[ZIP|PKZIP]], it sported many more options, some of which were unique during that time (archives over multiple disks/volumes, fine-tuning of the compression algorithms used based on the data that was being compressed, recovery records to recover from simple transmission errors, etc.).
 
ARJ was one of the leading compression tools during the 1990s. While it was a bit slower than [[ZIP|PKZIP]], it sported many more options, some of which were unique during that time (archives over multiple disks/volumes, fine-tuning of the compression algorithms used based on the data that was being compressed, recovery records to recover from simple transmission errors, etc.).
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=== ARJ software expiration ===
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If you wish to use or research the official ARJ software, be aware that some of the free/evaluation and beta versions of ARJ and ARJ32 have a hard-coded expiration date. They do not work, or do not work as well, if they think they are being used after that date. Expiration can manifest in several ways.
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The 0.xx versions disable some features, based on the system clock, and the timestamp of the file being archived. Other versions only seem to care about the system clock.
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Some beta versions inexplicably print "CRC error!" if they're expired.
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At least one version prints a message about a time delay, but then seem to hang forever.
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Newer versions have a time delay whose duration depends on how long ago they expired. The delay can be several minutes.
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The newest versions that don't expire are apparently ARJ 2.76 and ARJ32 3.09.
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Suggest running expired DOS versions in [[DOSBox-X]], which lets you set the clock.
  
 
== Format details ==
 
== Format details ==
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* [[Konvertor]]
 
* [[Konvertor]]
  
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''Ed. note: Newer versions of unregistered ARJ/ARJ32 have a hard-coded expiration date, and may have a long delay when you run them (several minutes, if it's been a long time since expiration).''
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''See also the notes about software expiration, elsewhere on this page.''
  
 
== Sample files ==
 
== Sample files ==

Revision as of 17:45, 7 June 2022

File Format
Name ARJ
Ontology
Extension(s) .arj, .a01, ...
PRONOM fmt/610
Wikidata ID Q2693033
Released 1990 (beta), 1991 (v1.00)

ARJ is a compressed archive format, and associated software. It was developed by Robert Jung.

Contents

Discussion

ARJ was one of the leading compression tools during the 1990s. While it was a bit slower than PKZIP, it sported many more options, some of which were unique during that time (archives over multiple disks/volumes, fine-tuning of the compression algorithms used based on the data that was being compressed, recovery records to recover from simple transmission errors, etc.).

ARJ software expiration

If you wish to use or research the official ARJ software, be aware that some of the free/evaluation and beta versions of ARJ and ARJ32 have a hard-coded expiration date. They do not work, or do not work as well, if they think they are being used after that date. Expiration can manifest in several ways.

The 0.xx versions disable some features, based on the system clock, and the timestamp of the file being archived. Other versions only seem to care about the system clock.

Some beta versions inexplicably print "CRC error!" if they're expired.

At least one version prints a message about a time delay, but then seem to hang forever.

Newer versions have a time delay whose duration depends on how long ago they expired. The delay can be several minutes.

The newest versions that don't expire are apparently ARJ 2.76 and ARJ32 3.09.

Suggest running expired DOS versions in DOSBox-X, which lets you set the clock.

Format details

Compression methods

ID Name Description
0 stored No compression
1 compressed most LZ77+Huffman. For decompression purposes, these are all more-or-less compatible with LHA's "lh6" method.
2 ...
3 ...
4 compressed fastest LZ77
8 no data, no CRC
9 no data

Identification

An ARJ archive starts with signature bytes 0x60 0xea.

The full identification algorithm used by the ARJ software is given in its technical documentation.

See also

Specifications

Software

See also the notes about software expiration, elsewhere on this page.

Sample files

Links

Retrieved from "http://fileformats.archiveteam.org/index.php?title=ARJ&oldid=42760"
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