Archive and Compressed Files
An archive file is a file that contains other files. It's a bundle
of files packaged together. Groups of files that belong together are
archived because it's easier to move one bundled file from one
place to another than it is to transfer many individual files, one at a time.
Most archived files are also compressed (shrunk in size) during the archiving
process. A bit about how file compression works.
Life, not already sufficiently complicated to suit software developers,
provided the opportunity for the development of different kinds of archivisational
methods. Archive types can be distinguished by the file extention. The most
common are .ZIP, .ARC, .LZH, and .ARJ for PCs; (.SIT for Macintosh).
Each of them (and the other less commonly
used archive types) each require a different utility (i.e. small program) to
extract the individual files.
One more file extension is worthy of note. Archived files with an .EXE extension
(.SEA for Macintosh) are self-extracting files. No separate utility is required.
Compressed files are files that have been temporarily shrunk to
make it easier to transfer them from one place to another. Frequently,
compressed files are bundled together and
archived, as described above, so that groups of files can be
transferred as one file.
There are untold numbers of compression methods. They work by searching
for and replacing characters with codes. By analyzing actual data content,
strings of blanks can be replaced with a code that represents them.
Some replace long sequences of repeating characters with one occurance of
the character and a number. For example, a sequence of 50 spaces is
replaced with one space and the number 50. Some compression programs
create a dictionary, a table that stores information.
Groups of characters that occur more than once are replaced with codes.
For example the word, "Rumplestiltskin," if it occurs more than once, is
replaced by a short code. The dictionary provides the means during
the decompression process to restore the original words and characters.
Back to Archive files
Encoded files serve a different purpose. They enable files
to be sent as email file attachments.
PC UTILITIES
WinZip
PKWare
MAC and PC UTILITIES
Zip-Unzip software
Almost all Macintosh computers can now accommodate .ZIP and other PC files.
Macs that weren't originally designed to do so, can be adapted with a "Mac-PC Exchanger".
(It's Part # M1252LL/B. Current cost is about $75.00.)
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