Wikipedia:Reference desk/Archives/Computing/2011 February 14

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February 14[edit]

Two questions:[edit]

1. Is the Asus U81A-RX05 still on the market, and NOT as a secondhand?

2. My computer says it can't detect an operating system, when there was one. But I don't have an OS CD, so how do I rectify this situation? (talk) 06:51, 14 February 2011 (UTC)

1: A quick googling suggests "no", but that's at the big stores that show up first in Google searches. It might be available on the shelf at some smaller computer stores that haven't sold through their inventory. #2: What OS? My first suspicion is that there has been damage to, or erasure of, the first few sectors on your hard disk. Personally I would go and buy an external USB hard disk to be a backup device, then I would use a friend's computer to download the Ubuntu boot CD and burn a copy, then back at the damaged computer I'd boot the Ubuntu CD and see if it can detect your hard disk. If so, back up everything you care about to that external USB hard disk. Then it's time to borrow a boot disc from a friend (make sure it is the same OS version you used to have) and boot the damaged computer from that disc, and choose the "Repair" option, if available. Comet Tuttle (talk) 17:15, 14 February 2011 (UTC)
My computer is running Windows XP, and to be honest I can't find anyone with a back up Windows XP OS recovery disc, nor do they sell them. So am I screwed here? (talk) 06:55, 15 February 2011 (UTC)
I wouldn't say you're screwed. One option you have is to buy a new hard disk and install a newer version of Windows on it, and hook up your old hard disk as a second drive. If your system is a desktop PC then this is pretty easy; if it's a laptop PC then you'll probably have to buy a USB hard disk enclosure for the old drive. Boot up the PC with the new version of Windows and see if it can read the old hard disk's contents. Then copy all the files you can from the old hard disk to the new hard disk. And let us know what happens. Comet Tuttle (talk) 21:20, 17 February 2011 (UTC)


Can I install 32 bit windows 7 on 64 bit hardware? —Preceding unsigned comment added by (talk) 10:57, 14 February 2011 (UTC)

Check This It will solve your all problems RahulText me 13:31, 14 February 2011 (UTC)
I'd like to know the answer to my question before I buy any computers. The software you link to requires one to already be in possession of a computer. (talk) 13:49, 14 February 2011 (UTC)
You can install a 32 bit OS on a 64 bit system. The limitation is that you will be running a 32 bit OS. You will not able to run 64 bit applications on the 32 bit OS. -- kainaw 13:50, 14 February 2011 (UTC)
Thanks (talk) 13:59, 14 February 2011 (UTC)
In the specific case of Windows (although also with many other OSes you'll get a similar issue) you're liable to be limited to about 3GB, any more RAM will go unused. Nil Einne (talk) 15:46, 14 February 2011 (UTC)
This question made me wonder if a 16bit OS like DOS could run on 64bit hardware. I know you can't run 16bit programs on 64bit Windows because it only emulates a layer for 32bit programs, but could DOS work directly on the 64bit hardware? (talk) 19:11, 14 February 2011 (UTC)
You can install something like qemu to emulate a 16-bit processor and install a 16-bit OS, but you won't be able to natively run a 16-bit OS on a 64-bit processor. Depending on the model, the 64-bit processor either has 32-bit hardware or a 32-bit emulator inside the 64-bit processor. It will not have 16-bit functionality. I suggest qemu because it emulates known "features" of some of the older chips that are needed to get old programs that used very bad programming practices to run. -- kainaw 20:12, 14 February 2011 (UTC)
Actually 64-bit processors (to be precise: x86-64 compatible ones) behave just like an old x86 processor ("legacy mode") until they are switched to long mode, which is needed to run 64-bit code. In legacy mode it should be able to run any old 16-bit code, and even in long mode it is (as I just learned from the article) still possible to run 16-bit code in protected mode. See also this table. --Tokikake (talk) 10:42, 15 February 2011 (UTC)
I had seen an attempt to install DOS6.2 on an AMD64. It failed. I will try it to see if it is truly the processor or something else that caused it to fail. -- kainaw 13:30, 15 February 2011 (UTC)
I don't know about the DOS 6.2 issue although I'm pretty sure I've run some version of 16 bit DOS on a AMD64 comp before for bios updates and the like (while there are a few 32 bit DOS and lots of DOS extenders, most are 16 bit AFAIK) and this possibly includes DOS 6.2 boot disks of some type (I've had an AMD64 comp since 2005). Also I'm currently running a rather old AMD64 computer with XP x32 (running natively) and Alley Cat (video game) and other 16 bit apps run fine (well as fine as they do on XP and the WoW or NTVDM DOS layers). Of course, they don't work on XP x64 or other 64 bit Windows versions without an emulator. Nil Einne (talk) 08:32, 16 February 2011 (UTC)
I tried it at home last night. Swapped out my drives in my computer. Put in an old IDE drive. Downloaded an old 16-bit DOS. Made the floppies (which required digging in the closet for an old floppy drive). The result - no go. It doesn't appear to be a CPU problem. It appears to be that DOS doesn't support the other hardware like the AGP video card. It starts to install and then there is no video. The USB keyboard/mouse stop responding (pressing caps-lock does nothing). I have to hard-reset. -- kainaw 13:21, 16 February 2011 (UTC)

Clear Screen C++[edit]

I am messing around with a MUD (Rom v2.4b6 is the codebase) and I am running into a problem trying to clear the in-game screen of text. I am using Cygwin for windows to compile. Here is what I am trying to do.. You log into to the text game and a new user types in their character name, and they choose a password. At that point their character is created and they go on to choose a sex, race, class and other things. This is how it looks:

Enter a name: Joeblow

Welcome, New user.

Choose a password: *****

Reenter password: *****

Welcome to the game!

Please choose a sex (M/F):

What I want to happen is after it says Welcome to the game I want a whole new blank screen to appear to continue the character creation process (at the top of the new screen would be Please choose a sex (M/F), instead of continuing on the same screen as above). I have tried:

printf ("\033[2J");

And that doesn't work. I even tried enabling ANSI.SYS but nothing changed. I also tried system calls "cls" and "clear" but all that did was clear the screen on my cygwin terminal window, not inside the actual game.

If there is anyone out there that can help me with this, I would be greatly appreciative. Sorry for being so overdetailed but I am just trying to get the idea out there of what I am trying to do. I've seen other MUDs accomplish this so I know it is possible. Thank you! —Preceding unsigned comment added by (talk) 15:03, 14 February 2011 (UTC)

I do not understand what you mean by "inside the actual game". The only aspect of being in the game is that the user knows is the terminal. So, if the terminal screen is cleared, the game screen is cleared. By understanding what you mean better, it may be possible to come up with a suggestion. -- kainaw 15:44, 14 February 2011 (UTC)
I don't understand what you mean about game vs. console, but wouldn't an old-fashioned:
for (int i = 0; i < num_screen_lines; ++i)
do the trick if nothing else will? --Sean 15:54, 14 February 2011 (UTC)
How are you connecting to (not starting) the game? You distinguish your terminal window from the game, so it must be a network connection (as it should be). If you're just using telnet, it may not support the ANSI codes. --Tardis (talk) 16:25, 14 February 2011 (UTC)
You might want to use a terminal library like ncurses. ncurses can give you programmatic access to more complicated terminal behaviors, including clearing the entire visible screen, editing characters on previous lines, and so on. If you are strictly using the C or C++ standard I/O library, you only have the capability to print characters, so you'll have to "clear the screen" by printing a lot of blank lines. Nimur (talk) 18:04, 14 February 2011 (UTC)

I'm totally unfamiliar with the ROM (MUD) system, but based on general programming experience it is very likely to contain a set of functions for managing the display, and you will need to use one of those functions to clear the display, or bad things will happen. If the system works like every other I have seen, it maintains an internal memory of what the display shows, and if you try to clear the display using some external means, you will probably leave the internal memory in an inconsistent state. Looie496 (talk) 18:10, 14 February 2011 (UTC)

Thank you for your responses and trying to help with my issue. Fortunately someone on another forum provided me a line of code that cleared the screen and it works perfectly in most telnet apps (it doesn't work in MUSHClient and GMud as they don't allow clear screen). Here is the code just in case this could help anyone else in the future:

write_to_buffer( d, "\x1b[2J\x1b[H", 0 );

Again thanks for trying to help. ANSI codes are a weird and mysterious thing.—Preceding unsigned comment added by (talk) 00:31, 16 February 2011 (UTC)

rm -rf / on Linux[edit]

Does the Linux rm command recognize / as being special, or does

sudo rm -rf /

actually remove the entire file system? -- Bk314159 (Talk to me and find out what I've done) 17:40, 14 February 2011 (UTC)

It will attempt to unlink the entire filesystem, but will most likely fail before completing the task. I used "unlink" because it removes the references to all files, but does not remove any of the files. Often, a system may be restored when only references have been removed, but it is very painful to do so. -- kainaw 17:55, 14 February 2011 (UTC)
For example, attempting to rm the device files in /dev/ will fail in most Linux and Unix systems, regardless of your user rights. Other filesystems and mount points may also fail to unlink, unmount, or delete, depending on your flavor of *nix. Nimur (talk) 18:01, 14 February 2011 (UTC)
See rm but also a bug about it: the behavior may not be consistent. --Tardis (talk) 18:28, 14 February 2011 (UTC)

root directory ¦ Reisio (talk) 18:50, 14 February 2011 (UTC)

Unix provides the superuser with nearly endless possibilities, this includes the possibility to shoot yourself in the foot. There's a reason why sudo displays a warning when you run it the first time, see Sudo#Design. -- (talk) 20:01, 14 February 2011 (UTC)
Because Ubuntu completely misses the point of sudo. :p ¦ Reisio (talk) 20:31, 14 February 2011 (UTC)
I'm rather sure I saw sudo's warning message on Linux long before Ubuntu even existed. Now get off my lawn! ;-)-- (talk) 22:50, 16 February 2011 (UTC)
No doubt after it was properly configured. ¦ Reisio (talk) 13:45, 17 February 2011 (UTC)

Even the task manager wouldn't come up on Firefox[edit]

At a library with Mozilla Firefox and Windows XP, the computer completley froze for about ten mintues shortly after being turned on. One time I was told this was due to the virus updates. On one occasion when I knew no one could help me except with CTRL-ALT-DEL, I decided to try that just to see what would happen. The list of options, including task manager came up, and I chose "task manager". I saw a list of what was going on, and I don't remember what I did, but everything unfroze. Yesterday, however, the task manager wouldn't even come up. I got the list of options but when I clicked on "Task manager", nothing happened for the longest time, and I couldn't get anything to work. Eventually, though, the computer unfroze. It must be pretty bad if even the task manager won't come up.Vchimpanzee · talk · contributions · 19:16, 14 February 2011 (UTC)

Is there a question here? The Reference Desk isn't your blog. (talk) 19:37, 14 February 2011 (UTC)
Yes. Why would the Task Manager not come up?Vchimpanzee · talk · contributions · 22:04, 14 February 2011 (UTC)
Because it took a very long time to load? This seems rather obvious from your description. If the computer is still using Windows XP there's a good chance it's still a single core with very little RAM which undoutedly doesn't help Nil Einne (talk) 22:58, 14 February 2011 (UTC)
There are any number of conditions that can cause a computer to lock up so that the Task Manager is no longer available. One example might be if the CPU overheats. StuRat (talk) 08:14, 15 February 2011 (UTC)
Nil Einne, I'll ask someone if this is the case. StuRat, the black box was making a lot of noise but it had just been turned on. There are some numbers on it, since I'm here. HP Compaq with a Celeron. Without my bifocals, I'd better not attempt these numbers. It says Windows XP Home Edition. That's strange. This is a library. The problem is relatively rare. One idea I came up with is the next time this happens if the Task Manager comes up I could write down those letters and numbers that come up on the screen. I didn't think of that when it happened.Vchimpanzee · talk · contributions · 15:36, 16 February 2011 (UTC)
I posted what I believed were the numbers for this computer, or thought I did. Maybe I clicked on "Show preview" and never got past it. Anyway, I have my bifocals on and I am absolutely certain the computer is a hp Compaq 220 MT, which is what I attempted to post yesterday.It also has Windows XP Home Edition, which is strange since this is a library. Obviously the updating done for the software wouldn't be printed on it, but M3C38-GTY2V-73WGM-FVPGM-4RR4Y mean something.Vchimpanzee · talk · contributions · 23:22, 17 February 2011 (UTC)

GPL and other Open Source licenses[edit]

What's the point of forbidding closed source forks of open source projects if, by definition, closed source projects are those whose source code is kept secret and, therefore and in theory, one can't prove that GPL'd source code has been used? --Belchman (talk) 19:50, 14 February 2011 (UTC)

Just because they may be keeping the source code secret doesn't mean it's impossible to figure it out. [1] Reach Out to the Truth 19:59, 14 February 2011 (UTC)
More examples: List of software license violations ¦ Reisio (talk) 20:41, 14 February 2011 (UTC)
Indeed. The Software Freedom Law Center [2] and other organisations have been extremely successful in enforcing the GPL so far. In general, if you can demonstrate reasonable suspicion, any court will ensure that the source code is made available for the purpose of the lawsuit, so that the copyright status can be determined. For the US situation, see Discovery (law). --Stephan Schulz (talk) 20:24, 14 February 2011 (UTC)
The Gnu General Public License explicitly forbids "forking" to a different license if the original software is derived from software licensed under the GPL.
If you have GPL-licensed software and source-code that you want to limit distribution, a more strategic approach might be to release the software under the GPL, and enter into a mutually consented business contract not to redistribute the software or source-code. (Just because your license legally permits the customer to redistribute the program doesn't mean they must redistribute it - especially if they have no economic incentive to share the program they just paid for). And if the customer doesn't redistribute the program, they don't need to redistribute the source-code either. There's actually a good case for using GPL'ed software to legally protect commercial free-software from price deflation. The GPL license protects the software author's rights to redistribute or resell their creation, while simultaneously giving the software users the right to modify it. This can help keep the sale-price of the software non-free, while preserving the freedom to examine and modify the source-code. See the article Gratis versus Libre Also, have a look at the Official GNU policy on Selling Free Software - they "encourage people who redistribute free software to charge as much as they wish or can."
Of course, a party may violate the terms of any license agreement, whether it is GPL or any other license, in contravention of license agreements, contractual obligations, and local laws - and incurs any legal liability for doing so. This only really matters if some legal entity pursues the license violator - which is often prohibitively expensive for creators of free software. Nimur (talk) 21:01, 14 February 2011 (UTC)

A company that tries to develop closed code from a GPL'ed code base is going to be highly susceptible to blackmail, explicit or implicit, from its own programmers. It wouldn't be a very intelligent approach. Looie496 (talk) 23:20, 14 February 2011 (UTC)

Thanks. --Belchman (talk) 00:25, 15 February 2011 (UTC)

iNAC managed access blocking of prison phone calls - how does it work, and is it the same as the suppression of cell phones at political protests?[edit]

I read about a California trial of "managed access" to block calls from smuggled cell phones in prisons. While it sounds like a straightforward idea, I am wondering how general this control is, and whether adoption of the system will make it even easier for governments or others to block or intercept people's calls.

The system "routes mobile calls originating in the prison to a third-party provider that check's each number to see if it's on a whitelist; if it doesn't make the cut, the call is blocked.[3]

Now even in the early 90s I remember that one feature of major political protests in the U.S. is that every cell phone in the area goes dead. I've since seen similar reports from half a dozen other countries - it sounds like it's always a surprise to people when it happens, even after all these years. I'd always just assumed that someone gave a call to have a local cell tower shut off or something, but after reading about this system, I wonder if they've been using the "managed access" approach all this time. If I understand correctly, it implies that there might be some sort of recognizable truck in the police response to a major protest, which carries the "third party provider's" mini cell phone tower. It also suggests, for example, that the identity of every cell phone in the crowd at any such demonstration is automatically logged as a part of this process.

Can anyone shed more light on how this process works? Does widespread adoption imply any change in how cell phones work for the general public? What are the most relevant articles? Should a stub article be started at iNAC managed access or is there some better name? Wnt (talk) 21:19, 14 February 2011 (UTC)

The "managed access" you describe sounds like a microcell or picocell attached to a specialized phone network. A phone locks onto the strongest signal available for its network, so if the strongest signal is from such a device, your phone wouldn't see any further-away free-world access points.
This is distinct from just shutting off cells in an area. I have no idea of when or whether this is done for protests in the US, though it would not surprise me -- telecoms companies are heavily regulated, and government is very much in a position to demand such a thing. But keep in mind that cells also support a limited number of calls, and in crisis situations (most famously 9/11) they can easily becomes saturated. --FOo (talk) 08:26, 16 February 2011 (UTC)
Thanks! I doubt it was overload - I saw it happen in a rather sparse crowd, where larger events routinely occur in Chicago. But your article led me to use "cellular base station" as a search term, with which I found reference to "Triggerfish" (we have no article on Wikipedia about anything but the fish), also known as "cell-site simulators" or "digital analyzers". [4][5][6][7][8] All of the references I've read focus on the uses of the system for surveillance, evading what small legal requirements may exist for obtaining phone information; but clearly if this technology works as you describe, it is capable of generally denying cell phone coverage to a defined area, even by 'accident'. Wnt (talk) 04:57, 17 February 2011 (UTC)
Based on the information I found, I started the article Triggerfish (surveillance). Feedback and assistance would be most welcome. Wnt (talk) 07:59, 17 February 2011 (UTC)

iPhone 3GS with an old bootrom[edit]

Does the iPhone 3GS model that has the old bootrom check SHSH blobs (i.e., is there any hardware based authentication)? --Melab±1 22:07, 14 February 2011 (UTC)

The Art of computer programming[edit]

I am confused by The Art of Computer Programming by Donald Knuth. Obviously Vols 1-3 are published and available. Is/Will Vol 4 be one big book or 3 books (4A, 4B, 4C)? What is available NOW, what will be available later this year? What is a Fascicle? Do Fascicles 0 to 5 equal Vol 4A? Will DK live long enough to finish Vols 5,6 and 7 - especially if Vol 5 isn't out til 2020?

My main reason for asking is that I don't want to buy things twice and I would prefer to buy the books when they are as big/collected as they'll ever be. In my simplistic world that would be 7 books. But if Vol 4 will always be 3 books then 9 books. I think the Fascicles are things I don't want.

Guidance appreciated - the WP: article wasn't clear enough. Thanks. -- SGBailey (talk) 22:42, 14 February 2011 (UTC)

Professor Knuth has been "preparing" the 7th volume since... about 1981. I don't think it's available in its entirety and it is doubtful if it ever will be. The authoritative place to check is Professor Knuth's "recent news" page, and the official Art of Computer Programming website. "Fascicles" are sort of like a few related chapters released as an "addendum" unit; so far, a few have been officially distributed to the publishing houses, and a few others are available "locally." With due respect, the wording on his webpage is a bit fatalistic, the expected completion date is listed as 2020, and I doubt he will ever "complete" the book. Nimur (talk) 22:52, 14 February 2011 (UTC)


how do i use a voice changer with skype — Preceding unsigned comment added by Tomjohnson357 (talkcontribs) 22:54, 14 February 2011 (UTC)

What is happening? General Rommel (talk) 07:59, 15 February 2011 (UTC)