TechWhirl (TECHWR-L) is a resource for technical writing and technical communications professionals of all experience levels and in all industries to share their experiences and acquire information.
For two decades, technical communicators have turned to TechWhirl to ask and answer questions about the always-changing world of technical communications, such as tools, skills, career paths, methodologies, and emerging industries. The TechWhirl Archives and magazine, created for, by and about technical writers, offer a wealth of knowledge to everyone with an interest in any aspect of technical communications.
Dan Gallagher wonders: <<Can anyone shed light on the longevity of CDs?
I hear differing opinions.>>
Perhaps because they're referring to different types of CD? A
mass-produced commercial CD has mechanical pits stamped into the medium
to create the bits, and will last almost forever (at least until the
backing starts to flake off or you leave it on the dashboard of the car
long enough for the plastic to melt).
CD-Rs and CD-RWs are created by heating a spot of dye in the medium
using a laser for long enough that a magnet on the drive can flip the
polarity of that spot and make the dye either reflective or
nonreflective. That's what stores the bits. Temperature changes and
high magnetic fields can conceivably damage the CD, since the
temperature change is well below the "melting and flowing like wax"
temperature, and the dye itself degrades over time, which is why you'll
typically hear stable lifetimes of less than 10 years for these CDs.
Check the manufacturer's specs for details on actual lifespans.
<<Is it safer to archive data on HD or CD? I'm talking long term, like
with a growing collection of digital pictures for example.>>
Magnetic media (hard disks etc.) are generally less stable because of
domain creep (the stored "bits" can blur together after enough time has
passed). This is much less of a problem than it used to be, but will
eventually happen. Moreover, they're more likely to get trashed by a
surge of electrical power (e.g., if you like working during
thunderstorms). Recopying the data solves the problem at least in part
by restoring the original strong signal, but you still need external
backups in case the hard drive gets toasted. In the long term, there's
a more serious concern:
<<will my little daughter be able to view images on a CD ten, twenty,
thirty years from now?>>
Depends on the format, and how gently you treat your CDs. File formats
do eventually go away and get replaced by superior formats (anyone seen
a VisiCalc or Wordstar file in the past 10 years? <g>). Although modern
formats such as JPEG are more advanced and are thus more likely to have
longer "legs", there's always a risk that at some point the file
formats will no longer be readable by the available software.
The only really good protection against this is to keep an eye open for
major format changes, and when they occur, copy your files into the new
format. For example, if the GIF copyright is asserted vigorously, at
some point you'll no longer see support for GIF files, which will be
replaced by PNGs or something even more advanced.
--Geoff Hart ghart -at- videotron -dot- ca
(try geoffhart -at- mac -dot- com if you don't get a reply)
ROBOHELP X5: Featuring Word 2003 support, Content Management, Multi-Author
support, PDF and XML support and much more!
TRY IT TODAY at http://www.macromedia.com/go/techwrl
WEBWORKS FINALDRAFT: New! Document review system for Word and FrameMaker
authors. Automatic browser-based drafts with unlimited reviewers. Full
online discussions -- no Web server needed! http://www.webworks.com/techwr-l
---
You are currently subscribed to techwr-l as:
archiver -at- techwr-l -dot- com
To unsubscribe send a blank email to leave-techwr-l-obscured -at- lists -dot- raycomm -dot- com
Send administrative questions to ejray -at- raycomm -dot- com -dot- Visit http://www.raycomm.com/techwhirl/ for more resources and info.
