Wikipedia:Reference desk/Archives/Computing/2014 April 4

= April 4 =

What physical principle was used to differentiate a hole from no hole with IBM punched cards?
Was it a conductor and its contact surface the card was dragged between able to conduct on a hole but not able when there was no hole? Or some other principle? 75.75.42.89 (talk) 01:23, 4 April 2014 (UTC)


 * See Punched card. Various IBM (and other) card readers through the years used mechanical, electromechanical, optical, pure electrical (electrographic), and probably other methods of reading. --Carnildo (talk) 01:37, 4 April 2014 (UTC)


 * Maybe I'm blind, but I didn't see any even cursory descriptions of the inner workings of card readers of different technologies at Punched card. 75.75.42.89 (talk) 09:10, 4 April 2014 (UTC)


 * We have an article on Punched card input/output but that is also woefully inadequate.--Shantavira|feed me 11:57, 4 April 2014 (UTC)
 * A bit in keypunch. I never did much with keypunch, but the missile system I started on in 1978 used punched tape. The tape reader had recently been upgraded from whisker contacts to optical (used the same light bulb as the VW dome light). --  Gadget850talk 12:34, 4 April 2014 (UTC)


 * And for Tabulating machine. This shows a 19th century method, but thimbles of mercury soon passed out of style. Jim.henderson (talk) 12:31, 4 April 2014 (UTC)


 * For a electromechanical system, the hole is sensed by an angled conductive brush - if a hole is there, the brush end goes through it and contacts a conductive roller on the other side of the card, completing a circuit; if there's no hole, the card prevents the brush touching the roller. A diagram, for an IBM model 82 card sorter is here. Textbook on Management Information Systems By D P Nagpal (which I found on Google Books) has a schematic diagram for this, and for an optoelectric system, with a bulb on one side and a photocell on the other (fig 3.7 page 66). There's more info about the brush system in this page. A logical diagram of the electrical circuitry behind the brush sensor reader is at this page. Even Herman Hollerith's original systems (patent US395782) were electromechanical, unlike a purely mechanical system like a player piano. -- Finlay McWalterᚠTalk 13:18, 4 April 2014 (UTC)
 * Our article Plugboard discusses how early card readers worked in some detail.--agr (talk) 19:28, 7 April 2014 (UTC)

Filtering Hindi characters in Unicode
I'm working on Hindi tweets (in Python) and have to scrape away every other language that appears in the each tweet other than Hindi. Is there any way I can specify a range of Unicode values which applies only for Hindi characters so that non-Hindi characters are removed automatically (excluding punctuation marks, which I want to keep)? La  Al qu im  is ta  06:03, 4 April 2014 (UTC)
 * You would probably want to use the Devanagari Unicode block which is in the range U+0900 to U+097F. --Canley (talk) 10:53, 4 April 2014 (UTC)

not responding
Firefox (latest version, 28.0) freezes 3-4 times a day, for about 10 seconds, with the message "not responding." Adobe Reader (v. 10.1.9) has also done so, and I believe other applications as well. What gives? Anything I can do about it? I have an HP 2000 laptop running Windows 7. --Halcatalyst (talk) 13:50, 4 April 2014 (UTC)


 * Similar problems on my (older) laptop are caused by an anti-virus scan running to schedule, and also occasionally by my lack of memory (with lots of pages being switched in and out of pagefile.sys) You might like to run performance monitor (and resource monitor) to see if any programme is hogging resources.    D b f i r s   08:12, 7 April 2014 (UTC)
 * Thanks, I have a similar setup. I'll try your suggestions. --Halcatalyst (talk) 17:16, 10 April 2014 (UTC)

How to recover my bookmarks after a Windows 8 refresh?
I have used Windows 8’s “Refresh your PC without affecting your files” option, and I have lost in the process all my Firefox and Chrome bookmarks. No restore point had been created prior. — Preceding unsigned comment added by 69.123.17.140 (talk) 14:23, 4 April 2014 (UTC)
 * I fear that there's no way to recover it. In future consider using Firefox Sync. Hunsu (talk) 12:05, 5 April 2014 (UTC)
 * If you use Chrome and were signed into a Google account in Chrome, you should be able to just sign in with the same account you were using before and your bookmarks should still be there Palmtree5551 (talk) 18:11, 9 April 2014 (UTC)

How do people get a hold on e-mail addresses?
A couple of times, I received e-mails of job offers. They usually make the job too good to be true (high salary, low requirements, no resume/CV, no company identification). Often, I get suspicious of these e-mails, so I never reply to them. What irks me is the fact that these people somehow know my academic e-mail address, which I never publish anywhere or even use to receive subscriptions on any website other than school-affiliated websites, except ClusterFlunk.com, which requires an .edu web address, because it's a website created for students. Even so, I received spammy job offers even before I knew of ClusterFlunk.com. 140.254.227.76 (talk) 15:01, 4 April 2014 (UTC)


 * Do you have friends (assuming that you email them using the address you're talking about) who just can't stop clicking on things, opening strange attachments or installing Banzai Buddy-type stuff that random banner ads told them to install? That's often the way that the contents of people's email address books end up in the hands of spammers and scammers. --Kurt Shaped Box (talk) 15:22, 4 April 2014 (UTC)
 * i.e. BonziBuddy —Tamfang (talk) 05:09, 5 April 2014 (UTC)


 * Email address harvesting is a way of obtaining large numbers of emails for illegal purposes. Getting yours swiped is hard to avoid if you spend any time at all with email. The best way not to get burned is to remember, as you're doing, that if it's too good to be true, it isn't true. --Halcatalyst (talk) 15:27, 4 April 2014 (UTC)


 * University emails are usually pretty easy to guess. If you had a list of students from somewhere, you could churn through combinations of first.last@[university name].edu (or whatever) and most of them would be correct. APL (talk) 15:33, 4 April 2014 (UTC)
 * It's the same with corporate email addresses as well. Most companies follow a pattern.  So just being familiar with that pattern is enough to get most people's email address correct.  And to follow up on what was said above, many people use their work email address for personal business.  (I see quite a bit of it doing tech support.)  It wouldn't be surprising if one of those people also clicked on a link for malware which scraped their contact list.  And finally, you don't mention if you are a student at this school or faculty.  If you're faculty, your email address is likely listed somewhere on the school's web pages.  Dismas |(talk) 15:53, 4 April 2014 (UTC)


 * It's also worth googling your email address (within quote marks) occasionally to see if it's being harvested from a website somewhere.--Shantavira|feed me 10:33, 5 April 2014 (UTC)
 * Spammers also combine, for example, known Hotmail accounts with the yahoo.com extension. It's really time we stopped spam. All the best, Rich Farmbrough, 17:17, 10 April 2014 (UTC).