Version 2.70 is the latest version of PKZIP for Windows and is
meant to be used for users using Microsoft Windows and includes
some of the below features.
The ability to create self extracting EXE files
Support for ZIP, TAR, GZIP, MIME, BinHex, UUecode, and XXencode
PKZIP FOR DOS
Version 2.50 is the latest version of PKZIP for DOS and is used
at the command line of MS-DOS and includes the below features.
How do I ZIP files that are larger than one diskette onto multiple
diskettes?
To do this you
would use the below syntax.
pkzip [directory] [diskfilename] -&.
Example:
pkzip c:\windows\*.* a:\windows.zip -&.
The -& is the important part of the above line and is telling
pkzip to place your files onto multiple disks.
Will I be able to unzip a program with Winzip I zipped in PKZIP?
Assuming the file was
zipped correctly, any
file with the .zip extension will be able to be pkunziped as will as unzipped in Winzip or
any other compression utility that is able to read .zip extensions.
Do you have a listing of available switches used at the command line?
PKUNZIP (R) FAST! Extract Utility Version 2.04g 02-01-93
Corp. 1989-1993 PKWARE Inc. All Rights Reserved. Registered version
PKUNZIP Reg. U.S. Pat. and TM. Off.
-3 Disable 32-bit instruction usage on 80386 or higher CPU's
-^ Echo the command line
-+ Disable Expanded Memory (EMS) usage
-- Disable UMB/HMA Memory (XMS) usage
-) Disable 32 bit DPMI usage
You can default any of these options with the PKUNZIP environment
variable. Consult the file ADDENDUM.DOC for further information.
PKWARE, Inc
9025 N. Deerwood Drive
Brown Deer, WI 53223
How PKZIP and most other
compression software work:
How Does PKZIP work? PKZIP uses several methods of compressing data by
using seek out and eliminate redundant information within a file. With the redundant
material removed, the file takes up less space. And because the information was redundant,
PKUNZIP can easily restore that material when it unzips your file. An example, consider
the below line, which you might find similar in a word-processor document:
The rain in Spain falls mainly on the plain.
Normally the above statement would take 44 or more bytes of disk space
because of the amount of words in the document. But this simple line contains a surprising
amount of repetition. The letters in and the space after the word in are
repeated at the ends of the words rain and Spain in the sentence. The
sequence ain occurs four times, the two-character sequence n plus a space occurs
twice, and the three-character sequence he plus a space occurs twice. What if you replaced
each duplicate occurrence of one of these strings with a special code, called a token, that
would stand for the duplicated numbers? each token would contain a much shorter number
combination that told you how many characters (including spaces) to count backwards in the
string and how may characters (including spaces) were duplicated. Then the line would look
like:
The rain <3,2>Sp<9,4>falls m<11,3>ly
on<16,2>t<34,3>pl<15,3>.
Data compression works because the string's original form can be
reconstructed based on tokens, for example, when PKUNZIP encounters <3,3>, it counts
back three characters from the beginning of the token and replaces the token with the tree
characters it finds there. Tokens recorded in a file by means of a special technique that
enables them to be stored in less space than the bytes they replace. In other words, a
token such as 3,3 can be stored in less space than three bytes it replaces. If the token
took up more space than the bytes it was replacing, there wouldn't be any point in using
it. The key to data compression is the ability to search a string of bytes, identify any
duplicated sequences, and replace the repeated bytes with short tokens. With only 44 bytes
to work with, a short string like the example above must have a lot of duplication if the
data compression is going to be worthwhile. But the longer the string, the more likely it
is to contain receptive information that can be replaced with tokens.
