21.002 Some of my downloads are bad; what's wrong?
Description
This article is from the Apple II Csa2 FAQ, by Jeff Hurlburt with numerous contributions by others.
21.002 Some of my downloads are bad; what's wrong?
If the exact length of a downloaded file is different than its exact
length on the download site (e.g. as shown via your FTP client program), the
download is probably corrupted. (Text files are something of an exception-
- i.e. the download length may be different and the file may have characters
added; but, usually, the "corruption" has no damaging impact.)
A common reason for getting a bad download is that a binary file-- e.g. a
.shk, .dsk, etc. file-- was downloaded in Text mode. (See discussion about this
in Q&A 001 above.) An FTP program should be set to "Binary" before doing most
downloads from ftp sites. If using a browser, pick one which defaults to binary
mode for unrecognized file types (e.g. a current version of Internet Explorer).
Some files may seem to be corrupted-- i.e. 'not work right'-- even if a
length check shows that the download size is identical to the file's size on an
ftp site. One possibility is that the file was corrupted somewhere in the
upload process. This is fairly rare for files made available for download.
A few Apple II files still include a Binary II prefix. This may cause the
file to appear corrupted to some utility you try to use on a PC; but, it will
work fine once transferred to your Apple II. (Normally, a modern Apple II
telecom program such as Spectrum or ProTERM will be set to automatically strip
off the Binary II prefix during transfer. GS-ShrinkIt and 8-bit ShrinkIt will
remove a Binary II prefix from .shk, etc. ShrinkIt files.)
The file may be okay but incorrectly named. For example, an .sys or .bin
file may be shrinked but still uploaded as an ".sys" or ".bin" file (instead of
".shk"). Or, an .shk file may be uploaded in binscii form as an ".shk" file.
(Such a file should end with ".bsq".) When a downloaded .shk or .sdk file is
rejected by ShrinkIt, it's a good idea to try running it through Binscii or
GScii. Sometimes the result will be a genuine .shk or .sdk file.
Other kinds of files are just misunderstood. A user who downloads a 'disk
image' file named NarfGame.dsk.gz" may conclude it is "corrupted" when it is
rejected by an emulator program or fails to convert to diskette with DSK2FILE
or ASIMOV. But, all that's required is to decompress the .gz file using WinZIP
or similar utility to produce a true .dsk disk image file.
A source of possible confusion for IIgs users is the occasional .shk or
.sdk file which looks fine but is rejected as damaged by GS-ShrinkIt. The
problem may be that the file was created by a Mac owner. Sometimes these Mac-
created Shrink files unShrink fine using GS-ShrinkIt; sometimes, not. Before
trashing a "damaged" .shk or .sdk IIgs file, try running it through Balloon.
----------------------------
By: Greg J. Buchner
Balloon is a IIGS desk accessory that was put out by Ego Systems...it
handles ShrinkIt archives from anywhere you can access a New Desk Accessory on
the IIGS. For the Mac, you'd use Shrink II.
By: Rubywand
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