Newsgroup: it.comp.hardware.modem
Titolo: Errori CRC: in che cosa consistono, come si risolvono?

Utilizzando il "monitor di sistema" di windows 98 mi ritrovo la
finestra degli errori CRC sempre impostati a 1....
è un problema? Come lo risolvo?
Grazie!
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dall'help di winzip..
WZ91 - CRC Error
About CRC Errors
A CRC error indicates that some data in your Zip file is damaged.
CRC stands for “cyclic redundancy check”. It is a calculation
made from all the data in a file to insure accuracy in
transmission. When you add a file to a Zip file, WinZip
calculates a CRC value for the file and saves the value in the
Zip file.  When you later extract the file from the Zip file,
WinZip® calculates the CRC of the extracted file and compares it
to the value stored when the file was zipped.  If these two CRC
values do not match, the file that was extracted does not match
the original file, and WinZip will display a “CRC Error” message.
When the data in a Zip file is damaged, it may not be possible to
extract all of the files from the Zip file correctly.  Damaged
data can affect the entire Zip file, multiple files, or just one
file.
Why CRC Errors Occur
There are many possible causes for data damage. Among the most
common is telephone line noise or some other transfer error when
downloading a Zip file from an online source such as the
Internet, AOL, or CompuServe.  Such an error can introduce
invalid data into a Zip file.  Some other possible causes include
exposure of disks to excessive temperatures or magnetic fields,
cross-linked disk sectors, and mechanical problems with disk
drives.
What to do if a CRC Error Occurs
The best solution to the problem of a damaged Zip file is to try
to obtain another copy of the file.  For example, use your backup
copy of the file or get a new copy from the original source. If
you obtained the Zip file by downloading it, then downloading it
again will almost always solve the problem.
CRC Errors on Removable disks
If the damaged Zip file is on a removable disk, the removable
disk may be physically damaged, or the data on it may have been
corrupted.  In these cases, the only completely reliable solution
is to use another copy of the disk or Zip file that is undamaged.
There are, however, two other situations in which it may be
possible to recover some files from a removable disk.
·	The removable disk drive that you are using to unzip the
Zip file may be malfunctioning.  Try using a different disk
drive, if possible.
·	If the removable disk drive you are using to unzip the
Zip file is not the same drive that was used to store the Zip
file on the removable disk, and you have access to the original
drive, try using this drive to unzip.  It is possible that the
original drive may be able to read the disk; if so, you can
extract your files using this disk drive (and have your removable
disk drives checked out--at least one of them may be out of
alignment).  Otherwise, the removable disk itself or the data on
it is probably damaged.
A “Last Resort” for CRC Errors
If you cannot download a new copy of the Zip file, obtain a
replacement disk, or use a backup copy, you may still be able to
recover some of your files, and even save portions of the files
that are damaged in the Zip file.  Here is the recommended
procedure.
1.	Start WinZip, switch to the Classic interface, and open
the damaged Zip file.
2.	Select Extract from WinZip's Actions menu, or click the
Extract button on the WinZip toolbar.
3.	In the Extract dialog, check the All Files option button
and select the folder into which you want to extract files. Then
click OK.
4.	WinZip will extract any undamaged files to the selected
folder; for any damaged files, WinZip will display a CRC Error
message. For each such file, before clicking OK in the error
message window, use Windows Explorer to open the extract folder
and look for the file; some portion of it will probably already
have been extracted. Copy the partial file to another folder and
then click OK in the WinZip error message window.  This will
erase the partially extracted file from the extract folder,
leaving intact the copy of the file you made in the other folder.
Whether or not a damaged file partially recovered using this
procedure will be useful depends on the nature of the file, what
kind of damage there is, how much of the file was recovered
successfully, and what kind of program(s) use the file.  In some
cases, a partial file is of no use at all; in some cases, loading
a partial file into your application program and re-saving it
will completely restore the data.  In other (perhaps most) cases,
the result will lie somewhere between these two extremes--some of
the data will be recovered, and some will be lost.
Copyright © 1991-2000 by WinZip Computing, Inc.  All rights
reserved.
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