Allegedly, on or about 24 August 2013, g sent: > something very surprising, years ago, someone i know had a commercial > music cd that when you held it up to a light, it looked like a sieve, > but played without anything noticeable. Back when I was young, and dinosaurs roamed the earth, audio CDs came out as a brand new thing. Just about any that I looked at, in the same way, had that same look to them, and they all played fine. What we can see of the disc is nothing compared to how the laser read the disc, both in the microscopic size of the pits (that we can't see with our naked eyes), and how it automatically compensates for random small missing bits of data *scattered* throughout the stream - it's not a huge chunk of consecutive data being lost. On that note, it always amazed me that data CDs were ever possible. For a start, you can't just lose a bit in your data (or program) and carry on as if nothing happened, it all has to be precisely correct, and audio CDs are continually working through playback errors, all the time the disc is playing. Checksums can say the data is wrong, but if there's more than one bit wrong, you couldn't work out what the error actually was. With audio, you can make a guess, to fit a missing value between the two adjacent surviving values, but computing data doesn't have that sort of relationship with adjacent data. Storing the data more than once, as the old C64 floppy disc drives supposedly did, is an approach that lets you read a corrupted disc, so long as at least one copy of the data survived, but that halves your data storage size, and data CDs didn't do that. -- [tim@localhost ~]$ uname -rsvp Linux 3.9.10-100.fc17.x86_64 #1 SMP Sun Jul 14 01:31:27 UTC 2013 x86_64 All mail to my mailbox is automatically deleted, there is no point trying to privately email me, I will only read messages posted to the public lists. George Orwell's '1984' was supposed to be a warning against tyranny, not a set of instructions for supposedly democratic governments. -- users mailing list users@xxxxxxxxxxxxxxxxxxxxxxx To unsubscribe or change subscription options: https://admin.fedoraproject.org/mailman/listinfo/users Fedora Code of Conduct: http://fedoraproject.org/code-of-conduct Guidelines: http://fedoraproject.org/wiki/Mailing_list_guidelines Have a question? Ask away: http://ask.fedoraproject.org
