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- WHY_JAR.DOC November 1996
-
-
- This document describes the advantages of JAR.
-
- JAR FEATURES:
-
- 1) JAR has a 16-bit executable (JAR16.EXE) for DOS and a 32-bit
- executable (JAR32.EXE) for Windows 95 and Windows NT. The latter
- takes full advantage of 32-bit instructions and the "flat" memory
- model.
-
- Data compressed in one operating system can be decompressed in
- another. JAR also supports optional filename translation when
- extracting long filenames in DOS.
-
- 2) A major feature of JAR is the ability to use additional memory for
- better compression. Unlike most other archivers, the DOS version
- of JAR can use EMS or XMS memory to improve compression.
-
- Memory usage is fully customizable. You can specify how much
- memory to use or you can let JAR auto-detect the optimal amount.
-
- No matter how much memory has been used during compression,
- decompression requires only about 400K of memory.
-
- The JAR compression engine detects popular file formats to achieve
- an improved compression rate.
-
- JAR's compression speed is comparable with other archivers.
- Decompression works much faster than compression. JAR32.EXE uses
- 32-bit instructions and thus is even more faster and compresses
- better than the DOS version.
-
- Please note that compression results are highly dependent upon the
- type of data compressed. We think that today (September 1996) JAR
- achieves the BEST compression rate among ALL other popular
- archivers (ARJ, PKZIP, RAR, UC2, LHA).
-
- 3) Compared to the popular DOS archivers PKZIP, RAR, LHA, only JAR can
- archive more than 50,000 files at one time. This enables JAR to
- handle very large disk drives.
-
- 4) JAR provides the capability of archiving files to multiple volume
- archives no matter what the destination media. JAR can archive
- files directly to diskettes no matter how large the input files
- are.
-
- Moreover, JAR allows one the option of changing archive volume size
- or even the option of concatenating all of the volumes into one
- archive.
-
- The JAR data verification facilities help ensure reliable backups.
-
- 5) JAR provides the facility to store EMPTY directories within its
- archives. This makes it easier to do FULL backups and that come
- with EMPTY directories.
-
- 6) JAR supports multiple CHAPTERS in an archive concept.
-
- The advantage of a chapter archive over a series of separate
- archives of the same set of files is that space can be saved when
- files to be archived do not change or change slightly. One chapter
- archive can produce the same results as one hundred standard
- archive backups. In other words, one can update a chapter archive
- one hundred times and fully recover any one of those updates.
-
- Moreover, JAR uses a special compression method to optimize the
- storage of the file and its subsequent modifications. Each chapter
- may have its own comment and lock option. JAR keeps each chapter
- creation and modification time. There are also many special
- commands and options which allow flexibility with multiple
- chapters.
-
- 7) For data error recovery, JAR can store recovery records into an
- archive which allow the repair of that archive if slightly damaged.
- JAR also has a special command to recover still usable data from
- a VERY damaged archive.
-
- The JAR archive data structure with its header structure and 32 bit
- CRC provides excellent archive stability and recovery capabilities.
- In addition, JAR is the second archiver after ARJ that allows you
- to test an archive during an archive process. With other archivers,
- you may have already deleted the input files with a "move" command
- before you could test the built archive. There is an option which
- allows one to select an actual byte for byte file compare with the
- original input files during archiving.
-
- 8) JAR provides a security envelope facility to "seal" JAR archives
- with a unique envelope signature.
-
- 9) Unlike most other archivers, JAR also stores/restores the file
- creation and access time along with the modification time.
-
- 10) JAR provides a special command which dumps archive header
- information into a readable text file. This is to aid the
- development of third party JAR support programs.
-
- JAR also provides a special test command to check the reliability
- of JAR compressing and decompressing gigabytes of files with
- limited free disk space.
-
- 11) The great number of JAR commands and options allow the user
- outstanding flexibility in archiver usage.
-
-
- end of document
-