Wikipedia:Reference desk/Archives/Computing/2015 February 10

= February 10 =

Lifespan of photos stored on CD
I have been putting all my digital photos from my computer onto CDs and I've quite a collection by now. Unfortunately the cost of photo-developing is so high that I can only print them a little at a time. My question is how long will the photos stored on CDs last? I have pictures that are very precious to me and wouòd hate to lose them. THank you.--Jeanne Boleyn (talk) 16:26, 10 February 2015 (UTC)


 * CD-R says "an average life expectancy of 10 years"; this IBM expert says "between 2 and 5 years". -- Finlay McWalterᚠTalk 16:35, 10 February 2015 (UTC)
 * Of course, the computer you have 5-10 years from now may not even have a CD drive, and having data in a format you can't access isn't much better than losing it. Mr.Z-man 16:39, 10 February 2015 (UTC)


 * Which is why I have a USB CD/DVD drive, USB 3$1/2$ floppy and an old PC with 5$1/4$ floppy and Zip drive. I recently backed up a number of 5$1/4$ floppies for a client who uses then on a CNC machine running Windows NT 4.0 Workstation.
 * There is no specific answer, as the quality of CD-Rs vary, thus some may have a linger lifetime. It also depends on the storage. See disc rot and Compact Disc bronzing. --  Gadget850talk 17:33, 10 February 2015 (UTC)


 * It used to depend a lot on the manufacturer (back when I paid attention to this), and presumably still does. Different CD-Rs use different dyes (at least phthalocyanine, cyanine, and azo), and different reflective metals (gold being the most stable), and they're made to various quality standards; a poor quality disc may use a dye that fades or diffuses more quickly, may have defects that expose the reflective layer to oxidation, or may do a poorer job recording the data from the get-go, meaning that you'll have less time until additional degradation causes the error correction to fail. Historically, Taiyo Yuden was the only brand that was consistently attached to high quality discs, and that may still be true. Counterfeit TY discs are common, though, so you have to buy from a licensed distributor.
 * You can maximize the lifetime of burned discs by storing them vertically (to avoid warping) in a dark, cool, dry place. -- BenRG (talk) 18:16, 10 February 2015 (UTC)
 * Don't laugh but I store them in my bookcase. My living room is gloomy as it rarely gets sun. I recently came acoss an old CD from 2005 and the photos on it were perfect. Is it feasible to store photos on social networking sites like Facebook as I'm worried future computers won't even use CDs?--Jeanne Boleyn (talk) 18:29, 10 February 2015 (UTC)
 * I probably wouldn't use social networking sites over privacy and copyright issues. But storing them in the cloud somewhere is a good idea. That way, even if your house burns down and you lose your computer, CDs, and paper copies, there's still a backup. Online storage is really cheap. Most sites will give you 5-10 GB for free and you can buy upwards of 100 GB for a few dollars a month. See for a list of the major sites. Mr.Z-man 18:56, 10 February 2015 (UTC)
 * It doesn't even have to be anything as dramatic as a house fire to lose all your photos. A house break-in or vindictive partner can destroy everything.--Jeanne Boleyn (talk) 19:13, 10 February 2015 (UTC)


 * Think the OP may like a proper archival disk: . Then leave it up to his grand-children to transfer those images  to the yet to be released super-duper-galactic-data-storage -globes that will never, ever, become obsolete technology. But until that day comes...  he will be dead a long time  and become just forgotten family history...--Aspro (talk) 18:28, 10 February 2015 (UTC)

There are archival disks (that cost more, of course). I have some of them, but I don't know what the real lifetime is. As someone mentioned, Taiyo Yuden (now owned by JVC) are good, and they are the ones I normally use for every-day purposes. However, I would not rely on one type of media. I store my photos on multiple hard drives, as well as writing discs from time to time. Have several copies on different media. The files on my drives get copied to newer ones after a few years. Bubba73 You talkin' to me? 07:35, 11 February 2015 (UTC)
 * I also have a portable SSD that is in a safe deposit box. But it doesn't get updated very often.  Bubba73 You talkin' to me? 21:25, 11 February 2015 (UTC)


 * It's a common misconception that digital media will last longer than physical media. That just isn't true in most cases. Ask an archivist - if you want to preserve photos (and don't want to spend money and time on the collection every few years) then you print them on acid-free paper and store them someplace that doesn't have large changes in temperature and humidity. SemanticMantis (talk) 14:56, 11 February 2015 (UTC)

this article is relevant. Bubba73 You talkin' to me? 03:27, 14 February 2015 (UTC)


 * However, it seems that a format such as JPEG will be around for a long while. At some point, it will probably no longer be used, but there should be software to convert to newer formats.  And, as long as there is a description of the JPEG format, software could be written to read it.  Bubba73 You talkin' to me? 02:34, 15 February 2015 (UTC)

Gmail notifications
I'd like to be notified when I have new messages in any of my 10 Gmail accounts, but not by a method as intrusive as pop-ups. What I'd prefer is if, at the login panel where I select which account to log into, it tells me how many new messages are in each. Is there any way to do that ? StuRat (talk) 17:00, 10 February 2015 (UTC)


 * There is a Gmail Notifier for Firefox. I have not tested this. --  Gadget850talk 17:17, 10 February 2015 (UTC)


 * Thanks, but lots of reviews say that's buggy. Any other ideas ? StuRat (talk) 23:52, 11 February 2015 (UTC)

I really like Checker Plus for Gmail for Chrome. It offers unintrusive color-based notifications for multiple accounts. Matt714 (talk) 03:32, 13 February 2015 (UTC)

Why do programming languages developed abstractions, like classes?
Couldn't you just make a list of commands and list of lists? At the bottom you'll have machine code. And lists would be a sequence of stuff you want to be performed.--Senteni (talk) 21:45, 10 February 2015 (UTC)


 * Computer programs are a means for describing a computational process. People think the intended reader of that description is the computer (a compiler or interpreter or whatever) but that's mostly not so. The computer will take all kinds of inscrutable gobbledygook like machine code, brainfuck, or perl. What makes programming hard is that the complexity of all but the most trivial program quickly combinatorially explodes, so that it becomes so gigantic that it's beyond what a human mind can understand. We introduce abstractions, both in the language itself and in the programs we write with it, so we can hide much of that complexity. By this means we can reduce a complex program in an unfathomably vast space down to a sequence of manageable problems that are small and simple enough that we can fit them into our puny meat brains - so that we can adequately reason about them. Equally, most non-toy projects need to be understood by other programmers, and here again breaking the problem down into abstractions means we can communicate it in a means another person can digest. This problem, and this solution, is common with most technological artefacts and scientific problems - a jet engine and a white blood cell are also too complicated for their operation to easily fit into someone's mind in one go, so we decompose them into simpler components and try to explain the macro functioning of the system in terms of the behaviours of these black boxes. -- Finlay McWalterᚠTalk 22:14, 10 February 2015 (UTC)
 * Very good explanation, thanks. We may as well ask "why is there abstraction in mathematics?" - And the answers are very similar - abstraction allows more complex things to be done without getting bogged down in details. It also allows us to gain efficiency by focusing on similarities in otherwise different things, and to write things more succinctly. If we didn't have an abstraction like a vector space, then we'd be busy proving the same things over and over again for each different sample. SemanticMantis (talk) 14:53, 11 February 2015 (UTC)