to combine multiple files together for easier management of the data
(i.e. backup, mail attachments, sharing by FTP, torrent, cloud, or any
kind of network service, etc) as for the host filesystem all the data
will be treated as a single file rather than as multiple ones,
eliminating the overhead of handling multiple objects - for each single
file, locating the physical data on disk, locating possible fragments,
checking file level security permissions, and so on.
The idea of archiving files pre-dates .zip format by many years, as in
format (later superseded by TAR, released in 1979 and
standardized in 1988), and LBR format in
CP/M / DOS world in early '80s.
means to reduce size of data on disk encoding it to a smaller output,
employing various strategies to efficiently map (most cases of) a
larger input to a smaller output, i.e. using statistical analisys to
reduce redundancy in inputa data.
too, predates development of ZIP standard, as once the input files were
merged into a single output archive, the operation was often
concatenated to lossless data compression to reduce the size of the
archive using various utilities available at the time as SQ (DOS,
CP/M), CRUNCH (CP/M), and compress (Unix).
TAR format, for example, is still an uncompressed archive standard, and
uses external compressors, nowadays usually GZ (fast deflate based
compression, same as in ZIP format), BZ2 (more powerful compression),
XZ (modern, very powerful LZMA based compression - the default
compression algorithm used in 7Z format).
Learn more about similarities and differences in Lossless data
compression and Lossy data
compression. For general purpose compressed archive file,
however, compression means Lossless Compression, a 1:1 mapping of input
to a smaller output.
SEA's ARC format (1985) combined the archival and (lossless)
compression in a single pass, providing probably the first example of
general purpose of archive manager, which allowed both to spare storage
for backup, and save upload
and download bandwidth (and time) for sharing - at the time, mainly BBS.
A few years later, after a controversy with SEA about
work in PKARC, Phil Katz superseded previous works releasing PKZIP,
which knew great success due multiple factors, as superior speed and
efficiency, and being the specs released under public domain, and
having relatively few competitors in years of fast PC market expansion.
What is ZIP a file
is a lossless data
compression and archival format created in 1989 by Phil Katz,
implemented for the first time in PKWARE's PKZIP.
The ZIP file format specifications were released under public domain
and the format had long and lasting success, to the point often "zip"
is colloquially used for any generic compressed archive, and many
package formats are based on deflate compression and/or same or very
similar specs: Java JAR / WAR / EAR, Android APK,
Apple iOS IPA files (iPhone and iPad devices), Microsoft CAB and Office
WinZip 12.1 (2009) introduced the new ZIPX file format specifications
for identifying a
new archive standard which
supports newer and more powerful compression algorithms.
What RAR, ACE, 7Z files are
During '90s and beyond, multiple alternative archival standard emerged,
as ARJ, RAR (1993), ACE, and 7Z (1999), introducing unique
them from the growing number of competitors, in example:
Archival file format tends to be more geared towards powerful,
computing intensive features to enhance manageability of data (high
compression, strong encryption), rather than enhancing ability to work
on live data (rapid read and write access) like filesystems, even if
some archive management utilities offers various mechanisms to edit
or update data inside archives.
- usually, stronger compression ratio than ZIP at the
cost of slower operation - but that disadvantage would have been paid
off by slower transfer time (especially on slow and public networks)
of smaller output file
- multi volume archival, splitting the output to met
constrains as mail attachment size limit
- encryption, to enforce end user's privacy if the file
is stolen, or
passed through unsecure servers (unencrypted public network, or any
third party controlled channel as a mail server, or remote storage
- error detection and correction, to prevent extraction
in the event data gets corrupted (i.e. faulty connection, damaged disk)
and attempt recovery from known good data.
More choice in standards brought users more features and healthy
competition between standards (see comparison of archive
formats) and implementations, but also brought
the need for
flexible multi-purpose archival applications, like PeaZip, to deal with
different formats users may encounter, and to make full use of the
feature's potential of
the different supported file formats.
External online resources: AR (Unix), LBR (CP/M), SEA company, WinZip's
Topics and serach suggestions: what is a compressed file, file
archival, data compression,
PKZIP, PKWare, ZIP, RAR, TAR, ACE, 7Z, ZIPX, file format
what is an archive file, lossless and lossy compression, what is a zip
file, what is file compression and
archiving, how to zip a file, how file compression works.