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August 17

Hardware Accelerated AES Encryption

How does hardware accelerated encryption work? The processor performs the same algorithm whether it's done by the hardware or software, so how is it that hardware accelerated is faster? [EDIT:] I have a Intel Core i5 processor, just so you know. --Yanwen (talk) 00:42, 17 August 2010 (UTC)

See Parallel computing. By offloading work to a specialized hardware unit, the CPU is free to do other work, while a peripheral device computes the hash. This can actually speed up end-to-end processing for a workflow (even if the actual calculation of the hash is slower than it would have been on the CPU). It is also possible that the specialized peripheral uses some hardware, like vector processing or SIMD, to compute the hash in fewer clock-cycles than a general-purpose CPU. In either case, offloading the work from the CPU can also increase the throughput capability of the system (which is a different performance-metric than single-job execution time). The exact speedup or throughput improvement depend entirely on the characteristics of the workflow and the load. For a highly-utilized server that computes thousands of hashes per second, such accelerators are probably a good value; for a personal computer, you would rarely see any worthwhile benefit. Nimur (talk) 00:54, 17 August 2010 (UTC)

So there is a separate hardware unit just for computing the hashes and other AES operations... How is this different from your typical multi-threaded application? Wouldn't you get the same performance boost by using more threads? --Yanwen (talk) 01:24, 17 August 2010 (UTC)

Threads have to be executed on hardware. Creating more threads does not help unless there is idle hardware available to execute the thread. As for why you would want to use specialized cryptographic hardware instead of just adding more general purpose cores, there could be two reasons. (1) If you know exactly what the hardware is going to be doing, you can make it faster and smaller than general purpose hardware. (2) Cryptographic keys can be stored in tamper-resistant hardware so the unencrypted data goes in, the encrypted data comes out, and the general-purpose processors do not have access to the keys. Jc3s5h (talk) 01:55, 17 August 2010 (UTC)

Is this feature only available to Core i3 and above? How about Core 2 Duo? Is specialist software needed? --Tyw7  (☎ Contact me! • Contributions)   Changing the world one edit at a time! 03:31, 17 August 2010 (UTC)

AES instruction set lists the processors that support it. There are no Core 2 Duos or Core i3s on the list, and a couple of Core i5s are excluded also. Software needs to be rewritten to use the new instructions. The article lists some programs that have been updated. -- BenRG (talk) 08:57, 17 August 2010 (UTC)

Algorithms implemented directly in silicon are faster. Imagine your microprocessor didn't have a built-in instruction for integer addition, and you wanted to perform that operation on the contents of a couple of registers. You would have to implement an adder manually using primitive operations the processor did support. Each time you take the AND or XOR of registers A and B and store the result in register C, the processor has to decode the instruction, check that the previous operations writing to A and B have completed and wait for them if not, dispatch the values to the appropriate execution unit, and deliver the result to any pending instructions waiting for the write to C. The bookkeeping takes orders of magnitude more time than the logical operation itself. You'd probably need ~100 instructions and 50–100 cycles to add two 32-bit registers by this process, and multiplication would be far worse. In contrast, if there are ADD and MUL instruction implemented in silicon, the processor just has to get the source registers once, send the bits to the silicon gates, and get the result from the other end. The intermediate bits flow directly to the gates implementing the next step, without any of the overhead. That's why AES is faster with specialized instructions. AES makes use of operations, such as finite field multiplication, that have to be laboriously simulated on most microprocessors.

Parallelism is not really the issue. Depending on how Intel implemented AES, it might be possible to run an AES computation in parallel with operations like integer multiplication, but few applications are going to bother to do this. Maybe if you were simultaneously encrypting and computing a cryptographic hash of a message you could write a single function that did both and save some time. But this definitely isn't what gives you the speedup on raw benchmarks of hardware vs software AES. -- BenRG (talk) 04:17, 17 August 2010 (UTC)

Algorithms implemented in silicon are only faster than software if they are faster. (This is a truism, but BenRG's above statement is propagating a common misconception that hardware accelerators are somehow providing "magic speed-boosts"). There are loads of examples where a hardware-accelerator unit is actually slower than a CPU performing the same task. It depends on the implementation and the task. One problem with specialized hardware units is that they are rarely using the latest-and-greatest in CMOS process technology - so they can't be clocked as fast as an Intel CPU. (See these Discretix AES cards at 220 MHz). In that case, they are only faster at executing tasks if their instruction-set of optimized operations-per-clock outweighs their poorer clocks-per-second rate, compared to the CPU. But there are lots of reasons why a "slow" hardware accelerator might still be "better" - it might consume less power; generate less heat in a data center; increase throughput; reduce high-level software network transactions; it might be cheaper to purchase/operate according to a "dollars-per-million-transactions" analysis; and so on. And, in many cases, because it is specialized for a few important operations, a hardware accelerator does actually decrease end-to-end processing time. As far as parallelism, I can think of a perfect example - in fact, probably the most common example - let the CPU process data, and then encrypt it. If the CPU needs to time-share between processing- and encrypting, it is slowed down significantly (by an amount calculated with Amdahl's law); but if the CPU can spend 100% of the time processing, and then pipe data to an encryption accelerator, you have created a deep pipeline, improving throughput. Nimur (talk) 18:18, 17 August 2010 (UTC)

I was talking specifically about the AES instructions in newer Intel CPUs. I think the original poster was specifically interested in those instructions, though I see now that the original question you replied to doesn't say anything about that. So I think we're both right. -- BenRG (talk) 19:45, 17 August 2010 (UTC)

Ah, yeah. I wasn't even thinking about on-chip acceleration; I think the OP clarified to mean specifically the Intel AES instruction set; details are provided at the official Intel site. I have a feeling those extensions will put a lot of encryption-peripheral-manufacturers out of business... Nimur (talk) 21:03, 17 August 2010 (UTC)

Computer -> TV

I have a computer, want a TV, and don't want to buy a DVD player (I used to just watch DVDs on my laptop, but the screen is a tad small). If my laptop is the Apple macBook Pro from mid2009 and I buy the adapter to HDMI, can I plug into HDMI in my TV and watch movies and stuff on my TV from my computer.--173.58.234.169 (talk) 03:05, 17 August 2010 (UTC)

Most computers have an HDMI port. Even my Dell Studio 15 have one. If your computer have that port, just buy an HDMI cable and connect the computer to the TV that ALSO have the port. Note: Your TV have to have an HDMI port (found on most HD Tv's not old/cheap ones) as well for this to work. Even though your computer have an HDMI port or you buy an adapter, as long as your TV doesn't have the port, all your efforts are futile. The easiest way is to get a cheap DVD player (about £10-£20) which works with the standard RGB ports or the extremely old SCART port that is found on most TVs (even very old ones..or at least most very old ones I've seen). --Tyw7  (☎ Contact me! • Contributions)   Changing the world one edit at a time! 06:55, 17 August 2010 (UTC)

MacBook Pros do NOT have HDMI ports. I am 100% certain about this. I would need an adapter for whatever the thing is to HDMI and it means I might need to run it through another adapter too if that makes sense. So the question is, is using adapters feasible knowing Apple does not include HDMI ports?--173.58.234.169 (talk) 03:58, 17 August 2010 (UTC)

Our Macbook Pro article verifies that no MacBook Pro has HDMI, but Mini DisplayPort instead. Googling macbook pro hdmi yields several adapters that seem to cost around US$5. Comet Tuttle (talk) 05:40, 17 August 2010 (UTC)

You might have to consider how to get the sound to your TV - "...older 2009 line of MacBooks and MacBook Pros are unable to provide an audio signal through the Mini DisplayPort, and only do so over USB, Firewire, or the audio line out port instead (the April 2010 line of MacBook Pro, however, supports this15)." Astronaut (talk) 09:32, 17 August 2010 (UTC)

I don't use HDMI, just the regular VGA (with a MacBook, but really the same difference, albeit with a different converter), and the audio thing is not such a big deal — you just run it out of the Audio Out port. But yeah, all of this is very plausible and super easy to do in my experience. I watch Netflix InstantWatch and so on off of the TV all the time. Just make sure the TV has the right input ports. Most of them these days have VGA as well in my experience. I'm not sure there's any advantage to using HDMI or VGA in this particular situation? The resolution of the monitor mirrors what is on the laptop, which is already high-def. --Mr.98 (talk) 13:33, 17 August 2010 (UTC)

I am buying the TV in the near future. I also want to use the InstantWatch in addition to DVDs which is why the need for a cord. I would have assumed that quality is lost with regular VGA though and do newer TVs even have it if they have HDMI (I have been so focused on HDMI, I haven't even checked). I find a lot of retailer websites cryptic on what inputs and outputs are in a model that it is difficult. I have to admit going to the store is not a ton better except you can look. As to audio, what kind of cord is needed for that? Thanks.--173.58.234.169 (talk) 18:53, 17 August 2010 (UTC)

While most retailer websites are pretty thin on the details like exactly which ports are installed (and, I have noticed, they are sometimes wrong), manufacturer websites are a better source of information about their products. In my experience, not many TVs have a separate audio-in, but where I have seen audio-in it has always been via left & right RCA connectors (but maybe that's a European thing). The ideal way would be find a converter box to take video and audio from your MacBook Pro and send it to the TV with one HDMI cable. This MacWorld article, which discusses many of issues, recommends some specific products. Astronaut (talk) 09:10, 18 August 2010 (UTC)

Thanks, your solution seems best for what I am trying to do (the MacWorld one) and should work in the US.--173.58.234.169 (talk) 21:56, 19 August 2010 (UTC)

When I use VGA on my TV it looks pretty much identical to the input. If it is worse quality or refresh rate or colors or whatever, I certainly can't tell. But I'm not a hi-fi style buff or anything. The resolution is identical on my TV/laptop combination, which is all I am going for (it's higher than the InstantWatch resolution/refresh itself). I'm pretty sure it's pretty standard these days for at least a VGA port and standard stereoplug (e.g. "headphone') input to be available on newer LCD TVs, at least when I went looking at them. (I ended up just buying one at CostCo, after hunting around — they had the best prices, heads and tails above places like Best Buy.) More tricky in my experience is audio output, which is often in an optical plug, which requires you to use compatible speakers or to get some kind of converter. --Mr.98 (talk) 12:53, 18 August 2010 (UTC)

computer file with pdb extension

I got a computer file with pdb extinsion. I don't know how to open it. Any idea? thank you.124.43.25.100 (talk) 08:17, 17 August 2010 (UTC)

Is this any use? --Phil Holmes (talk) 09:26, 17 August 2010 (UTC)

It would help us if you told us what you thought the file was supposed to be. Is it a document someone sent you? And old set of notes? Something you downloaded from a website? --Mr.98 (talk) 13:35, 17 August 2010 (UTC)

For what it's worth, the .pdb files on my system exist because I use Microsoft Visual Studio. The .pdb file does nothing by itself. Is it in a folder along with some other software? Comet Tuttle (talk) 17:30, 17 August 2010 (UTC)

This is why it's important to say where the file came from. All the files on my system with a .pdb extention came from the Protein Data Bank and can be opened with a molecular viewing program. These programs, however, would do nothing with Comet Tuttle's Visual Studio file, though. -- 140.142.20.229 (talk) 18:30, 17 August 2010 (UTC)

We have articles or dab pages on most extensions, such as PDB. ---— Gadget850 (Ed) ^talk 19:54, 17 August 2010 (UTC)

2 anti virus software running together

Apart from slowing down your computer why shouldn't you use 2 AV softwares together, what happens when you do? Mo ainm~Talk

It can cause problems because the two (or more) programs aren't necessarily going to be aware of each other and can get in each others way when doing active scanning. Also, when a virus is found it can cause quite a "fight" as to who gets to deal with it. Personally though I use Symantec Endpoint Protection as well as Microsoft Security Essentials and they work together just fine even when something is found, so unless you actually have problems running two programs then I wouldn't worry about it. But assuming both programs are up-to-date then running more than 2 is probably overkill and will degrade your system performance with no real benefits.  ZX81  ^talk 18:51, 17 August 2010 (UTC)

As virus scanners can contain portions of actual virus code for identification purposes, rival AV suites can actually flag each other as 'rogue' programs when they see the code in their own scan. Exxolon (talk) 20:59, 17 August 2010 (UTC)

If you want to run two AV engines, there are products who offer that feature. So you would be running one AV product, but with two engines from different manufacturers, which avoids the issue of two AV products detecting each other's virus samples or similar problems.

If you want to do it manually, you should find out the names of the program directories and add a scanning exclusion for those (install AV #1, add exclusion, deactivate AV #1, install AV #2, add exclusion, activate AV #1). There's no guarantee that it will work, it's just increasing the chances. On-Access scanners might still get in a fight because they hook into file access routines, and basically have to hook into each other if more than one is installed.

I'd recommend going the several engines combined into one product way if you're looking for more protection than one AV can offer. Or you could install the On-Demand components of multiple AV products, add exclusions for them in the one On-Access scanner you run, drop all your "suspicious" files into one folder and add a batch file that triggers scanning of this folder with all your On-Demand scanners.

If this is for company use, you could use one dedicated AV scanning computer that runs a different AV than the rest of your machines, and make it a company rule that all media entering and leaving the building must be scanned there. Same goes for Web proxies, Mail servers, etc. - run a different AV on them than the desktop machines. -- 78.43.71.155 (talk) 09:04, 18 August 2010 (UTC)

Need input - writing a basic referrer tracking script

Hi,

I am want to learn more about how Google Analytics works by writing a 'basic' version of it which only tracks the referrer (initially) and the page being visited (its going on a template). I plan to implement the tracker using a 1x1 pixel approach, using the javascript like this one:

<script type='text/javascript'>
document.write("<img src='//my.tracker.url.here/pixel.php?args=" + someVariablesHere +"' width='1' height='1' alt='' /> ");
</script>

for the php side, i came across this php code to generate the actual gif image, and room for me to add the database part. Now some questions:

1. Which is more reliable for getting the referrer: Javascript (document.referrer) or PHP ($_SERVER["HTTP_REFERER"])?
2. Aside from the referrer, what other information is commonly collected?
3. is the syntax for the image source safe "//url.here.com" in terms of implying http/s or should I explicitly code it (detection using window.location.href)?

Open to advice regarding specifics and good practices. TIA PrinzPH (talk) 22:39, 17 August 2010 (UTC)

You could use a non-expiring tracking cookie with a globally unique id. You should write out the full url...probably using http: vs https. PHP is more reliable than javascript (server is always more reliable than client). Other information that could be collected could be duration of stay, mouse movements, client information (browser, OS, screen size, etc).Smallman12q (talk) 20:43, 18 August 2010 (UTC)

Thanks for the reply, will try it out! :) PrinzPH (talk) 20:04, 19 August 2010 (UTC)

You will notice that Google Analytics itself codes for the http/https distinction. I think the issue is that if you are in https and serve up unsecured content on some browsers, they will either block it or give a nasty warning message. --Mr.98 (talk) 15:43, 21 August 2010 (UTC)

Wikia's poor quality of service

Dear Wikipedians:

Is it just me or does anyone else notice that Wikia's quality of service seems really poor.

I started a new wiki today on Wikia, and I noticed these frequent "black-out" periods where the whole Wikia site seems to crash and not respond. I remember Memory Alpha and Uncyclopedia being really reliable in the past, but not anymore.

Anyone else know more about this problem?

Thanks,

70.31.154.183 (talk) 23:38, 17 August 2010 (UTC)

I stopped going to Wikia sites when they forced that horrible "New Monaco" skin on every wiki and stole uncyclopedias domain name, so I don't know what their service is like currently. But from past experience Wikia has always been quite slow with a lot of timeouts. They probably have an outdated server. 82.44.54.4 (talk) 11:13, 18 August 2010 (UTC)

Thanks. That about explains it. 70.31.154.183 (talk) 12:31, 18 August 2010 (UTC)

I don't see how you can claim someone stole the a domain name, when the owner apparently entirely voluntarily transferred ownership. If you're referring to transferring from www.uncyclopedia.org to uncyclopedia.wikia.com as the primary hosting location, that appears to be a seperate issue that happened long after ownership of the domain name was transferred. Nil Einne (talk) 16:42, 20 August 2010 (UTC)

Resolved

August 18

Surprising SEGV from read(2)

Resolved

Under what circumstances can this code cause a segmentation fault in read()?

#include<unistd.h>
#include<string.h>
int cread(int fd,void *buf,int sz) {
  memset(buf,0,sz);
  return read(fd,buf,sz);
}

Because the prototypes are there, sz will be properly promoted to a size_t. What does read() do (if, say, other memory is corrupted) that could cause it to fail? --Tardis (talk) 00:23, 18 August 2010 (UTC)

Well, trivially if fd is not a valid file descriptor (depending on the quality of your libc, of course). Can you verify if fd is valid? --Stephan Schulz (talk) 00:31, 18 August 2010 (UTC)

You're supposed to be able to call read(2) with an invalid descriptor and just get EBADF. fd==20 here, for what that's worth. --Tardis (talk) 01:06, 18 August 2010 (UTC)

If you're seeing this, I'd suspect that read is doing some pointer arithmetic that memset isn't, and that a vastly wrong value for sz is causing it to overflow or underflow, or perhaps memset has some internal check that's causing it to silently stop before it faults, a check that isn't done in read. I tried some trivially mad values for sz (-1, 0x7fffffff, 0x80000001) and it's memset that faults for me, but your libc, or your sz, may differ. -- Finlay McWalter • Talk 00:50, 18 August 2010 (UTC)

The thing that gets me is that read is a system call! The kernel needs no help from me to put bytes into that buffer, and I've already demonstrated that the buffer is legit. What pointer arithmetic could it possibly need to do? --Tardis (talk) 01:06, 18 August 2010 (UTC)

You haven't really tested that the buffer is legit - you're assuming that memset will have addressed all that memory, because that's what is contract appears to say it will. But what does memset really do when you give it a vastly, meaninglessly negative sz? Isn't it within is right to do nothing at all? If you really want to test the buffer is legit, you'll write the memory yourself with a loop. -- Finlay McWalter • Talk 01:15, 18 August 2010 (UTC)

True enough: its argument is unsigned, but it could in theory ignore very large values. But I also know that sz==67480 (and that the buffer is actually 512000 B long). --Tardis (talk) 01:51, 18 August 2010 (UTC)

Oh, and if buf is on the stack, and you trash the stack with an sz that's too big (or -ve), you can segfault in several ways - you can trash cread's stack frame, meaning it'll return to 0 (bang!) or (possibly with a -ve sz) mangle cread's copy of the pointer called buf, so that it no longer points to the actual buffer on the stack, but instead to 0 (bang!). That shouldn't be the case if buf is malloced, or is in .bss or .data, however. If that's the case, commenting out the memset should cause the read to succeed. -- Finlay McWalter • Talk 01:07, 18 August 2010 (UTC)

To clarify, I'm suggesting that memset is trashing the stack, but that you don't notice until the read. -- Finlay McWalter • Talk 01:09, 18 August 2010 (UTC)

buf is obtained from malloc(), but I think you're right about the stack; attaching a debugger shows that the pointer that triggers the SEGV points 440 MB above the stack pointer, and is itself on the stack — but then the SEGV shows up in a different function. When I let it die and look at the core, it says it died inside read() and with a completely different pointer. --Tardis (talk) 01:51, 18 August 2010 (UTC)

Ah, you're screwed then:) If the stack is corrupt, and you can't use tools to help, you're reduced to putting in canaries into the stack (just declaring autos with known odd values like 0x3f5c) and periodically checking them to see when they're intact and when they've been steamrollered. -- Finlay McWalter • Talk 02:09, 18 August 2010 (UTC)

When I've had to do that in the past, I wrote a little library with register_canary(addr, val) and unregister_canary(addr) which stored a little database of canaries. Another thread woke up every 1ms or so and verified all the canaries were intact. If one is missing it segfaults into the debugger deliberately. -- Finlay McWalter • Talk 02:14, 18 August 2010 (UTC)

In general, this is perfect fodder for valgrind or purify; you're seeing a segfault in read because that's where memory misbehaviour was detected, but if memory is already corrupted by some other bad code elsewhere, you'll never find the corruption by worrying about what read does. -- Finlay McWalter • Talk 01:19, 18 August 2010 (UTC)

Unfortunately, this is running under MPI, and is (of course) only failing in parallel; running it with such tools is rather more difficult than it would be otherwise. Thus my interest in a theoretical analysis that might point me at the right part of the code. --Tardis (talk) 01:51, 18 August 2010 (UTC)

Here's why you can't rely on one function accessing memory identically to another (particularly when passed pathological parmeters). Consider the following two (very naive) implementations:

  void simple_memset(char* p, byte n, int sz) { 
    char * d = p;
    while (d < (p+count)){
      *d=n;
      d++;
    }
  }

  void simple_read(int fd, char * p, int sz) {
    int bytes_read=0;
    while(bytes_read<sz){
      p[bytes_read++]=get_byte_from_file(fd);
    }
  }

Those both look like reasonable implementations. Now consider the following example, assuming a 16 bit address space (I'm too lazy to type all those extra 0000s, but the point is the same in 32 or 64 bits). Say your data segment is located at A000..BFFF, with buf 0x100 bytes beginning at B000. Now say you mess up and instead of passing 0x100 as sz you pass 0x7654. Inside simple_memset, at the beginning, d is 0xB000, p is 0xB000, and count is 0x7654. So p+count would sum to 0x12654, but that just truncates to 0x2654. As d >= 0x2654, simple_memset will terminate without writing any bytes. So that call to simple_memset hasn't validated you can access the buffer. And lo, look what happens when you then run simple_read. It works for a while, even reading far off the end buf buf at 0xB0FF, but eventually bytes_read gets to 0x1000 (which is allowed, because that's much less than 0x7654). It does that p[bytes_read++], where p is 0xB000 and bytes_read is 0x1000, so it's dereferencing memory at 0xC000, which is beyond the bounds of the data segment, and that's a segfault. -- Finlay McWalter • Talk 01:59, 18 August 2010 (UTC)

It was in fact stack-smashing, produced by a truly remarkably bad set of communication functions that sent the wrong data and then stored that incorrect data into (rather than through!) a pointer. I wish I could say that the code was ancient and written by some idiot long since departed, but in fact I wrote it on the 4th of this month, so… yeah. Thanks for reminding me of the obvious. --Tardis (talk) 02:32, 18 August 2010 (UTC)

Worse, that should generally generate a warning, and some idiot ignored that warning and thought "ah, I'll fix that later" :) -- Finlay McWalter • Talk 02:36, 18 August 2010 (UTC)

Unfortunately, generic interfaces like MPI offer no such type safety:

void recv3(int *p,int src) {
  MPI_Status st;
  MPI_Recv(p,1,MPI_INT,src,0,MPI_COMM_WORLD,&st);  /* convert int* to void*: OK */
  MPI_Recv(&p,1,MPI_INT,src,0,MPI_COMM_WORLD,&st); /* convert int** to void*: OK?! */
  MPI_Recv(*p,1,MPI_INT,src,0,MPI_COMM_WORLD,&st); /* convert int to void*: warning */
}

I may be that idiot, but I run gcc with -pedantic -Wall -Wextra -Wfloat-equal -Wundef -Wredundant-decls -Wpointer-arith -Wwrite-strings -Wshadow -Winline -Wdisabled-optimization -Wstrict-prototypes -Wunreachable-code. --Tardis (talk) 14:24, 18 August 2010 (UTC)

Lint (software) can often catch pointer and cast conversions that the -pedantic warnings do not catch... this chapter from Linux Clusters discusses the use of splint with MPI; I have never used that tool, but it looks like it can check for common argument mismatches in MPI functions. Nimur (talk) 20:33, 18 August 2010 (UTC)

wget

Would it be possible for wget to scan say 5 pages and then output a list of every link on those pages into a text file? 82.44.54.4 (talk) —Preceding undated comment added 11:35, 18 August 2010 (UTC).

Uhh, as far as I know, you can't do that using wget by itself. You could use wget to download the files you want, then use sed to process those files and filter for the <a></a> HTML tags. CaptainVindaloo ^{t c e} 19:07, 18 August 2010 (UTC)

It depends on what you need the URLs for. If you want to create a text file just to feed it back to wget at a later time, extracting the URLs is unnecessary. Just specify the downloaded page as input file and omit the URL(s) on the command line. See the help file for commandline options -i, -F (and you might need -B as well). -- 78.43.71.155 (talk) 20:31, 18 August 2010 (UTC) PS: Prithee, do tell: What are you up to? Creating a local copy of 4chan?

Mutation in Genetic Algorithms (optimization)

In the Mutation(GA) article, it is not mentioned where the mutation operation is used in the GA. Let's say there are N chromosomes in the last step, "old N chromosomes". I think there are three choises to create the new population.

1) N new chromosomes are generated from three different operations: a) Some are directly copied from initial population b) Some are generated by crossover c) Some are generated by mutation (This is the algoritm used in MATLAB's implementation)

2) N old chromosomes enter crossover, after mating and crossover N new chromosomes are generated. N new chromosomes enter mutation. Best N chromosomes are selected out of 2N chromosomes.

3) N old chromosomes enter crossover, after mating and crossover N new chromosomes are generated. Both N old and N new chromosomes enter mutation. Best N chromosomes are selected out of 2N chromosomes.

Which one above is true? OR can I use any of them? Kavas (talk) 12:19, 18 August 2010 (UTC)

I could be wrong, but I suspect you'll probably be better off asking this on the Wikipedia:Reference_desk/Science reference desk, this is computing and this doesn't (to me) seem related?  ZX81  ^talk 18:50, 18 August 2010 (UTC)

cf Wikipedia:Reference desk/Science#Mutation in genetic algorihms, yesterday. -- Finlay McWalter ☻ Talk 20:08, 18 August 2010 (UTC)

I asked that question too. But, as I use a numerical computing environment (MATLAB) for implementing the GAs, I thought "Computing Desk" should be more suitable. I'm not sure "mutational meltdown" refers to "stuck into a local minimum" there. Kavas (talk) 21:49, 18 August 2010 (UTC)

Reinstalled OSes, regedit, and Star Wars

I have Star Wars: Empire at War, and its expansion, both legally bought and paid for. I installed them on my computer. Then my OS (Windows XP Home) was eaten by viruses. I also had Windows XP Professional on the computer because I was aware that this might happen. I am now running XP Professional. The problem lies in that I still have Empire at War and Forces of Corruption installed, but not listed in the registry. Can you please tell me what registry keys are necessary for the game to run, and what their contents are? I would reinstall from disk, but I think my EAW disk 1 might be corrupted (it won't run the installation screen even if I go into the drive and run it manually), and FOC refuses to reinstall without EAW being reinstalled. Thanks! 97.125.84.72 (talk) 16:47, 18 August 2010 (UTC)

Sorry I don't know the answer to your question, however it's possible it's not just registry keys it needs, but also specific files in the Windows system directories. I'd simply contact LucasArts though, it might be a problem with something else that's stopping you from being able to install the game, but even if it is actually is a faulty disc they have a disc replacement policy where for only $5.00 USD per disc they'll swap your broken disc for a working one.  ZX81  ^talk 18:48, 18 August 2010 (UTC)

I solved this problem myself several days ago and am explaining here so that anyone else with the same problem will no what to do. I successfully installed Empire at War with another disk, then looked at the registry info. The registry key for the original EAW was "HKEY_CURRENT_MACHINE\SOFTWARE\LucasArts\Star Wars Empire At War\1.0\", containing: string "CD Key" with the CD key as its value; string "ExePath" as the path for the sweaw.exe executable file; string "Launcher" with the path for the launcher as its value; DWORD "Installed" with value 1; and DWord "Revision" with a value of 10105 (2779 in Hexadecimal). I created another registry key, "HKEY_CURRENT_MACHINE\SOFTWARE\LucasArts\Star Wars Empire At War Forces Of Corruption\1.0", and put in the strings for "CD Key" with my Forces Of Corruption CD key and "ExePath" with the path for swfoc.exe, and the DWord "Installed" as 1. It worked; although I used a noCD cracked executable and won't verify whether it would work without one because I fear SecuROM, which is deployed with the unaltered executables for FOC or EAW. 97.125.84.72 (talk) 06:31, 27 August 2010 (UTC)

Trying to install an MSDOS program on Vista

I just now downloaded the Shareware version of the original Duke Nukem game from http://www.3drealms.com/duke1, and upon opening the resulting zip file after completing the download, a window with a warning message appeared. Entitled "16 bit MS-DOS Subsystem", the window gave me the following text: "This system does not support fullscreen mode. Choose 'Close' to terminate the application." Any idea how to get this program to install on Windows Vista? Nyttend (talk) 19:35, 18 August 2010 (UTC)

DOSBOX 82.44.54.4 (talk) 19:42, 18 August 2010 (UTC)

Program is downloaded, and I've gotten it to work; thanks for the pointer. However, I'm now confused: how do I tell it to run the install program, or how do I tell the install program to run in Dosbox? I've looked and failed to find a "Run with" command when I rightclick on the install program in My Computer, and I can't remember how to work DOS; the readme for Dosbox doesn't seem to have a how-to-run-DOS element. Sorry if there's an obvious answer to my problem; I just can't think of how to do this. Nyttend (talk) 21:29, 18 August 2010 (UTC)

It will probably work if you just open the dosbox prompt and type the name of the executable, with its full path (e.g. c:\dowloads\duke.exe -- Finlay McWalter ☻ Talk 21:32, 18 August 2010 (UTC)

The program is called "INSTALL.EXE" and in a folder named "DUKE", but typing C:\DUKE\INSTALL.EXE results in a message of "Illegal command: C:\DUKE\INSTALL.EXE". Do I have to type something before the full path? "run" and then the path resulted in a message of "Illegal command: run". By the way, the readme says that I must follow a "mount" command; I don't understand what that does, but I've followed the readme's instructions and gotten the results that it said I should from that. Nyttend (talk) 21:43, 18 August 2010 (UTC)

You don't use RUN or anything, you just type in "INSTALL.EXE" after you have mounted the right directory as a drive in Dosbox. --Mr.98 (talk) 21:46, 18 August 2010 (UTC)

If Dosbox on Vista works the same as it does on OS X, what you do is install Dosbox, then you have to "mount" the directory with the program as a virtual drive within Dosbox (e.g. "MOUNT c d:\yourprograms\duke" makes it so that the C:\ drive in Dosbox corresponds to the folder on your D: drive as indicated). Then you run it from within Dosbox (e.g. "c:\duke.exe"). If you have forgotten your basic DOS commands, type in HELP and it'll give you them. --Mr.98 (talk) 21:45, 18 August 2010 (UTC)

Okay, it installed; the program isn't running properly, but I suspect that it's a compatibility issue. I'll try running it on an XP computer. Thanks, especially, for the HELP command; I had no idea that there was such a thing, but I was wishing that there were. Nyttend (talk) 23:10, 18 August 2010 (UTC)

There might be special Dosbox settings that will help. ("Dosbox -- all of the old frustrations of Dos, today!") I tried Googling "Duke Nukem Dosbox," and what do you know, someone has written a guide on getting it to work. Now some of this is about the CD-ROM version and probably doesn't apply, but I thought maybe it'd be a start. The Dosbox FAQ actually says specifically that it does run, but you have to be careful about selecting your graphics settings, because Dosbox is emulating the entire PC at once, and can't necessarily do it as well as the original hardware. This page has more specific .conf settings that might be of help. From the looks of things, Duke Nukem is a little hard to get started, because it — in its own day — pressed CPU resources pretty hard, and emulating that can be a little tricky. It seems do-able though. Good luck. --Mr.98 (talk) 01:14, 19 August 2010 (UTC)

Dammit, I should have posted this as soon as I saw your question and saved you some hassle. The easiest option is NOT to use the DOSBox directly but instead use one of the many graphical front-ends that have been developed for it. I'm partial to D-Fend Reloaded because of its nice interface listing all your games in the main screen one below the other, kinda like MAME does with arcade games. It has a "Add game" Wizard which takes you step by step through the process of adding a new game to the list (including the setup.exe or install.exe file), and its mouse-over tooltips are mostly quite helpful and explanatory. Zunaid 21:21, 19 August 2010 (UTC)

That's pretty good to know in general, thanks. --Mr.98 (talk) 16:31, 20 August 2010 (UTC)

Latest version of Netscape (and how to speed up netscape)

Hello there, I am using Netscape 9.0 Beta version 3. Is it the latest version? I am also trying to speed up the browser. So I found this (ehow.com/how_6001169_speed-up-netscape-navigator.html website). But the problem is, options mentioned in that article is not present in Netscape 9.0, for example, "Network Connections.", "Preferences" and "Connections" tab. Where could I get this option? thnaks--180.234.38.102 (talk) 20:52, 18 August 2010 (UTC)

No, the latest version of Netscape was 9.0.0.6 (from February 2008). If you are not already aware, Netscape is no longer actively developed. As explained on that history page, and our article Netscape Navigator, the technology that drove Netscape went through some complicated business dealings and ultimately emerged as the core for the Mozilla project. The newest version is Mozilla Firefox, Version 3.6.8. Nimur (talk) 21:10, 18 August 2010 (UTC)

(edit conflict)The most recent version is Netscape Navigator 9.0.0.6, released in February 2008. Beta 3 was released in August 2007, making it three years old now. If possible I'd recommend upgrading to a more modern browser. A more recent browser just might run faster. If not, those changes should still be possible with a new browser. Except possibly the first option, which I haven't seen in any browser that I've used. Reach Out to the Truth 21:13, 18 August 2010 (UTC)

It's probably best to update to the latest version of Netscape (9.0.0.6) or to switch to firefox. Netscape was abandoned in 2008, and is essentially replaced by firefox.Smallman12q (talk) 15:27, 19 August 2010 (UTC)

Wikipedia has a problem

Whenever I begin typing the URL to Wikipedia in Firefox, it will automatically suggest "en.wikipedia.org". However, the stored headline for that page is "Wikipedia has a problem". While it is definitely true that Wikipedia has its problems, this was not the headline of the page when I most recently visited it. It has been like this for quite a while, and I wonder if there is a way to fix this without purging all the stored URLs. Thanks, decltype (talk) 21:25, 18 August 2010 (UTC)

According to Wikipedia:Bypass_your_cache#Mozilla family hold shift and press the reload button to bypass your cache. Taemyr (talk) 21:33, 18 August 2010 (UTC)

Thanks, I've purged my cache but it didn't help. Perhaps my question was poorly worded — It is only in list that automatically drops down when I begin typing an URL that the headline is wrong. Regards, decltype (talk) 21:39, 18 August 2010 (UTC)

It sounds like a bookmark thing. Go to Bookmarks -> Organize bookmarks, search for the wikipedia link, highlight it, and at the bottom of the dialog box there should be some text boxes. Under "Name", change it to whatever you want it to say 82.44.54.4 (talk) 21:49, 18 August 2010 (UTC)

It's not a bookmark thing. Mine used to do that because of the recent serverdeath, but it's stopped doing it. sonia♫ 22:59, 18 August 2010 (UTC)

I'm not sure this will work, but clearing the entry may solve the problem. Start typing as you have been doing. When the mislabeled suggestion appears, use the down arrow to highlight it and then press the delete (DEL) key. Hopefully that will clear the entry and Firefox will get a new title the next time you visit the page. -- Tom N (tcncv) talk/contrib 00:23, 19 August 2010 (UTC)

Thanks all. Tcncv's suggestion kinda worked. The entry is gone, but it is not getting readded when I visit the URL in question. Not a big deal though :) Regards, decltype (talk) 04:36, 19 August 2010 (UTC)

August 19

X-Root

Hi.

   My question is one of mathematics. Does a program exist which can solve for X in the following equation, where Y and Z are known?

Y^X=Z

   Thanks. Rocketshiporion Thursday 19-August-2010, 5:43am (GMT)

Hi there. If you're just doing a quick calculation or two, you can do it with a calculator using logarithms. If Y^X=Z, then X log Y = log Z, so X = (log Z / log Y). You could put this into the language of your choice if you wanted to automate it. Brammers (talk/c) 08:07, 19 August 2010 (UTC)

Another way to view this is (and get the same result) by the definition of log. $\log {a}=b$ implies $10^{b}=a$ (if we are using log base 10, but any base will do for this definition). So, assume we are using log base Y. You have $Y^{X}=Z$, which implies $\log _{Y}{Z}=x$. The computer will not have log base Y, but to convert bases, you just divide by another base: $\log _{Y}{Z}={{\log {Z}} \over {\log {Y}}}$. And, from above, we know that ${{\log {Z}} \over {\log {Y}}}=X$. -- kainaw™ 15:03, 19 August 2010 (UTC)

The above assumes we're talking about real numbers. More generally, working with complex numbers, the solution may be multivalued -- see complex logarithm. 198.161.238.19 (talk) 14:50, 20 August 2010 (UTC)

Key Stroke Logger

Hi how to create a key stroke logger (software) using C++. Can you please give the details and the code?117.204.3.54 (talk) 13:10, 19 August 2010 (UTC)

Split off into new section Rojomoke (talk) 14:54, 19 August 2010 (UTC)

See Keystroke logging for details and google "open source c++ keylogger" for source. --Sean 15:19, 19 August 2010 (UTC)

There is an article on key logging at Keystroke logging. Your current request is overly broad...how do you plan to implement the key stroke logger: with an api hook, a blue pill hypervisor, or with a rootkit. The implementation is often system-dependent.Smallman12q (talk) 15:23, 19 August 2010 (UTC)

Without objecting to the question, can we stop this conversation somewhere short of giving explicit instructions on how to create one's own password-stealing trojan? If someone's going to try to hack into my machine, I prefer to know that they are smart enough to figure out how to do it on their own. --Ludwigs2 16:45, 19 August 2010 (UTC)

Or they were smart enough to avoid the hassle and simply slip a hardware keylogger on the keyboard input. -- kainaw™ 16:58, 19 August 2010 (UTC)

The good news, though, is that we can provide complete instructions and links to compiled programs, source-code, strategies, and everything: the information is all freely available to answer these sorts of responses and is easy to get. Fortunately, the people who want to use keyloggers invariably will find the instructions overly-complicated. Nimur (talk) 17:49, 19 August 2010 (UTC)

and let's keep it that way. I have a soft spot for intelligent criminals (call it anarcho-romanticism...), but I can't abide dumb ones. --Ludwigs2 18:15, 19 August 2010 (UTC)

Message digests

Is there any known message whose message digest after applying one of the encryption algorithms like SHA# or MD# is exactly the same as the original message? 20.137.18.50 (talk) 15:08, 19 August 2010 (UTC)

It may be remotely possible...but its highly unlikely.Smallman12q (talk) 15:23, 19 August 2010 (UTC)

It's not unlikely for a fixed point to exist. The chance of a good hash function having a fixed point is 1 − (1 − 1/n)ⁿ where n is the number of outputs, such as 2¹²⁸ or 2¹⁶⁰. For any realistic hash size, this is almost exactly 1 − 1/e, or 63%. -- BenRG (talk) 19:17, 20 August 2010 (UTC)

SHA# and MD# are hash functions, not encryptions, so your question is unclear. They don't affect the original message. --Sean 15:25, 19 August 2010 (UTC)

Of course I meant that the output of the hash function would be equivalent to the input to it. 20.137.18.50 (talk) 15:30, 19 August 2010 (UTC)

What you're asking in essence is whether there is a fixpoint for SHAx or MDx. It seems that no-one knows - that is, there is no analytic finding that says yay or nay, and brute force is a big job. This guy is apparently organising a brute force search for a fixedpoint in md5. While in theory such a finding might cast doubt on the security of a hash algorithm that had hitherto been thought secure, as long as they're fantastically rare (as, for example, are the weak keys of certain otherwise secure block ciphers) that probably wouldn't affect the practical security of a hash algorithm. I don't know of any evidence for either hash family that shows any algorithmic relationship between the tractable determination of collisions and the existence (or determination) of fixpoints. -- Finlay McWalter ☻ Talk 18:00, 19 August 2010 (UTC)

I wonder if there is an "officially" coined term for it in computing, rather than fixpoint. See some of the math behind it here.Smallman12q (talk) 18:07, 19 August 2010 (UTC)

Neither SHA-1 nor MD5 is perfect; that doesn't mean they necessarily have fixpoints. -- Finlay McWalter ☻ Talk 18:29, 19 August 2010 (UTC)

The term "fixed point" is reasonably common in computer science. It's an important concept; the Y combinator is used to find the fixed point of functions (in the lambda calculus, they're guaranteed to exist), and this can be used to make recursion happen. Paul (Stansifer) 19:11, 23 August 2010 (UTC)

The existence of a fixed point is not a weakness any more than the existence of collisions (which are a mathematical certainty, of course). Successfully finding a fixed point or a collision does demonstrate weakness. -- BenRG (talk) 19:17, 20 August 2010 (UTC)

When searching for a fixed point of a hash, how, precisely, do you describe the function? MD5 yields a 128 bit (16 byte) hash, but this is typically given as a 32 digit hexadecimal number, represented in ASCII with 32 bytes. Do you feed MD5 the 128 bit value or the 32 character string? The former seems mathematically "purer" in some sense, but the latter seems likely to be what most people would be interest in. -- 1.46.157.19 (talk) 12:23, 22 August 2010 (UTC)

Wouldn't they be equal? The 128-bit value when converted ASCII will yield the same result if the ASCII is converted to the 128-bit value.Smallman12q (talk) 14:54, 22 August 2010 (UTCle

No. The MD5sum of a 16 byte file consisting all of the value 0 will differ from the MD5sum of the 32 byte file consisting of all 0x30, the ASCII value of the symbol "0". A 128 bit file which yields a 128 bit MD5sum equal to itself is one sense of a fixed point, but so is a 32 byte file of ASCII characters whose MD5sum, in hex, represented in ASCII, is equal to itself. One such fixed point may exist while the other may not. -- 1.46.93.58 (talk) 00:37, 23 August 2010 (UTC)

MD5's output is defined to be a sequence of 16 bytes (RFC 1321, section 3.5). -- BenRG (talk) 23:04, 23 August 2010 (UTC)

I do think that a 16 byte fixed point would be of more interest to a mathematician doing anything other than a brute force search. The 32 byte "hex in ASCII" fixed point is almost more of a recreational mathematics question, as our choice or character representation is fairly arbitrary. You might as well be look for the 128 byte fixed point of the string which is the ASCII representation its hash in binary.

Still, the 32 byte fixed point is the fixed point of the function that returns a hex string, and it is much easier for the average user to verify, as they wouldn't need a hex editor to create the input file. "This guy"'s brute force search (mentioned above by Finlay McWalter) speaks of MD5 returning a "32-character, hexadecimal string" and states that "there could exist a string which, when hashed, returns itself" implying that he is interested in the 32 byte fixed point. Of the first dozen programs and scripts submitted to that site that I checked, only one searched for the 16 byte fixed point; the others searched for a 32 byte fixed point. -- ToE^T 12:36, 24 August 2010 (UTC)

Also of interest would be detection of a cycle of a hash function. They are guaranteed to exist, and repeated iterations of the hash from any starting point will eventually enter a cycle. Any fixed point is a cycle of period one. The hash is invertible on this restricted domain (domain restricted to its range) if and only if it is collision free over the restricted domain if and only if all cycles lack initial non-cyclic leads feeding into them. Barring unexpected properties of the hash, the birthday theorem should apply. So for MD5, on average it would take on the order of √(2¹²⁸) = 2⁶⁴ iterations of the hash to enter a cycle and complete one period, with the typical period being about half that. Note that 2⁶⁴ ≈ 18.4 billion billion and a billion seconds is over 31.5 years. I don't see how a search for the cycle resulting from a given starting point can be parallelized. -- ToE^T 18:25, 24 August 2010 (UTC)

IP addressing and correct program instance

Suppose someone is running two instances of the same program, for example, Firefox. Both instances send requests for information to the same IP address (for example, Google), but the instances are requesting different data. A packet arrives at the requesting computer. How does the operating system know which of the two instances the packet should be routed to? Jc3s5h (talk) 16:58, 19 August 2010 (UTC)

By creating an internal representation for each unique connection. Specific operating systems have different strategies: most Linux-like systems use connect() (on the client) and accept() (on the server) to re-assign the communication to any free port. In other words, both sides are initialized using the "known" port, but then are usually shuffled to a random, "temporary-use" port-number unique to the particular client/server socket-pair. After the initial connection is negotiated (e.g. on Port 80 for HTTP), the socket-pair gets reassigned to a different, free port. Correction - the server always uses the known "destination" port; only the client uses a randomly assigned "source" port; and the two ports (source and destination) form a uniquely-identifiable socket-pair between client and server. You can see this list of re-numerated ports if you use the netstat command. Nimur (talk) 17:15, 19 August 2010 (UTC)

Thanks, that is a clear answer. Jc3s5h (talk) 17:35, 19 August 2010 (UTC)

Just to make it clear, I don't think there's any shuffling. The source port is some randomly assigned port above port 1024, the destination port (the web server) is port 80. There's no port reassignment. The source port is (almost always) different than the destination port. On *nix machines (and maybe windows too, I'm not sure) non-root processes cannot open sockets below port 1025. Shadowjams (talk) 06:05, 20 August 2010 (UTC)

Ah, you're right. The server-side (i.e., whomever started with listen()) may choose to re-assign the port, but it is usually not necessary. There is enough state, provided by the IP-address and client-side random port, to allow multiple communications streams between the same host and same server that are initialized on the same server-port-number (each socket-pair between host and client is uniquely identified by the client's random port-number). Server-side shuffling is therefore optional, and uncommon. (FTP uses this technique, with a "side-channel" socket that I think can be randomly assigned on both ends, with specific ports negotiated through the first socket). Nimur (talk) 17:07, 20 August 2010 (UTC)

SP6a

I want to download service pack SP6a for NT4, but the download page from microsoft.com says "The page cannot be displayed because an internal server error has occurred" and has been saying that for months. Where can I download a proper version of SP6a, because the last one I tried was some kind of virus. 82.44.54.4 (talk) 17:07, 19 August 2010 (UTC)

I'm afraid you're not going to be able to get it from Microsoft as it's not been supported since 2004, although I did check Technet and MSDN just in case, but no. Although I have no way of verifying it's authenticity this page is by someone in the same boat as you who's uploaded a local copy to their server. The comments on the page (assuming genuine) seem to suggest it's okay. Normally I'd say you should always get it from the original source, but since this is going to be impossible I think that's probably the best you can do. Still, use at your own risk etc!  ZX81  ^talk 17:31, 19 August 2010 (UTC)

Thanks, that's awesome! There appear to be four different downloads. Which one is the best, "High Encryption", "Standard Encryption", "56-bit Alpha", "128-bit Alpha"? 82.44.54.4 (talk) 18:59, 19 August 2010 (UTC)

You probably don't want Alpha (you'd know if you did!) and most likely you want the first "High Encryption" link (128-bit). The Standard version is 56-bit because at the time there was legal problems with encryption higher than that and exporting to other countries.  ZX81  ^talk 19:09, 19 August 2010 (UTC)

It is simply bad practice to encourage the use of 3rd-party distributions of Windows patches - they are probably violating distribution licenses and are difficult to vet for authenticity. NT Server hasn't been developed since 1999 - so you should have started considering an upgrade in 1999 - and it has been officially EOL'ed for more than five years - this means you should have definitely stopped using it in 2004. (The grace-period of reasonable usage is long since expired!) There are dozens of cheap and low-cost alternatives from Microsoft to help you upgrade to a more modern version; and there are lots of free software alternatives if you have a zero-dollar budget; but we should not advise you to seek out unofficially-distributed upgrades for (obsolete, proprietary) software . Nimur (talk) 17:41, 19 August 2010 (UTC)

It's even worse practice to run the system unpatched. Besides, migration costs for that server is likely to be large. 121.72.203.118 (talk) 12:53, 20 August 2010 (UTC)

But ah, he is running it unpatched, as there have no doubt been exploits that affect NT4 SP6a that have not been addressed due to the aforementioned end of life taking place many many years ago. Using a patch from an unknown source to hold up such an old system is like playing Russian Roulette with two bullets instead of just one. --144.191.148.3 (talk) 14:21, 20 August 2010 (UTC)

It seems strange that Microsoft would remove the links to NT4 service packs when they still keep the old Windows 95, Windows 3.1 and DOS help pages and update packages available to view and download, with the "This article was written about products for which Microsoft no longer offers support. Therefore, this article is offered "as is" and will no longer be updated" disclaimer on them. Is there some specific reason why they removed NT4 downloads? 82.44.54.4 (talk) 18:59, 19 August 2010 (UTC)

They may not have deliberately removed it; it may simply be that it's no-one's job to maintain it any more, and some unrelated website change broke it and no-one's taking responsibility for either fixing it or removing the link entirely. -- Finlay McWalter ☻ Talk 19:31, 19 August 2010 (UTC)

If you have a chance to obtain SP6 (without the a), the patch to upgrade from SP6 to SP6a is still available here: http://download.microsoft.com/download/winntsp/patch/6.0a/nt4/en-us/q246009i.exe (Intel) / http://download.microsoft.com/download/winntsp/patch/6.0a/alpha/en-us/q246009a.exe (Alpha). -- 78.43.71.155 (talk) 17:11, 20 August 2010 (UTC)

Here's the most official download site I could find: ftp://ftp.lrz-muenchen.de/pub/comp/platforms/pc/winnt/sp6a/usa/ - obviously, it's not microsoft.com, but it's the official site of the computer centre for Munich's universities and for the Bavarian Academy of Sciences and Humanities (http://www.lrz.de/english/) so it's unlikely to be a hacked version. And as you can see from the file path, it's the US version of SP6a, not the German one. -- 78.43.71.155 (talk) 17:23, 20 August 2010 (UTC)

Virus embeds?

What kinds of files are viruses typically embedded in? Would a .pdf or an excel file be likely to infect a computer? What kinds of files are safe to back-up after a virus has infected a system? 138.192.58.227 (talk) 17:18, 19 August 2010 (UTC)

I think we can probably come up with a pretty good taxonomy of standard files viruses hide in, a pared down version of the information at Computer_viruses#Vectors_and_hosts. The obvious start:

• Executables. On Windows that means EXE and COM files in particular. No big surprise there.
• Scripts. Obvious Windows candidates are BAT and VBS (because most people won't have a system set up to run other scripting languages out of the box, I don't think).
• Files that can contain scripts inside of them. This is the big one, because all of the MS Office products can do this. So we're talking DOC, DOT, XLS, PPT, and MDB files at the minimum. Probably more.

Now the tricky bit is that last category, because what files can and can't have scripts embedded in them (in a way that they will actually execute, which is crucial), and whether their security can be compromised in weird ways, is a very big question. PDF viruses do exist, though I don't think they're common. Excel files, definitely, yes. As for backing something up after infection... it's a tricky proposition if you're going by just file name alone. --Mr.98 (talk) 17:50, 19 August 2010 (UTC)

Are there instances of viruses infecting your MSOffice files? Or are these only from downloading files that already contain the virus? 138.192.58.227 (talk) 18:56, 19 August 2010 (UTC)

Apparently they can be spread by worms. But there are millions of viruses — presumably there would be some that would mix-and-match their vectors. Again, approaching it from the standpoint of "what can be backed up" is a little tricky. --Mr.98 (talk) 19:22, 19 August 2010 (UTC)

This link explains how to disable macros in Microsoft Office. I believe that as long as Microsoft Office is set to ignore macros, Office files that have been infected do not pose a risk to you (now if you send them to someone else, you may infect them). Other Wikipedians will correct me if I'm mistaken.--el Aprel (^facta-_facienda) 03:23, 21 August 2010 (UTC)

That doesn't stop the ever-popular buffer overflow which doesn't function through macros, but rather through a handily crafted document.Smallman12q (talk) 23:12, 21 August 2010 (UTC)

What are the two types of pop-up ads?

This relates to a question I asked earlier. Most popup ads that get past the popup blocker have a URL at the top which cannot be changed, and most of them are small and rectangular. Then there are ads which have a changeable URL along with the back button, forward button, etc. that one would expect to see on a regular web page.Vchimpanzee · talk · contributions · 17:56, 19 August 2010 (UTC)

When popping up a window with Javascript, you can disable components of the browser window, such as the address bar, buttons, status bar, etc... Most browsers allow you to disable the disabling of window components. -- kainaw™ 19:44, 19 August 2010 (UTC)

What I'm saying is that there is no "address bar" as such in the window, or buttons, in most pop-up ads. I'm trying to figure out the correct terminology. I probably should have said pop-up window in my earlier question because the problem wasn't happening with a regular ad.Vchimpanzee · talk · contributions · 19:49, 19 August 2010 (UTC)

Kainaw is correct that it has to do with the specifics of the Javascript that launch the window, and how the browser interprets it. See, e.g. this page that describes the settings coders can use to customize the behavior of the popup window. Different browsers interpret these a bit differently — I don't think Firefox will let you totally hide the address of a page, for example, because of the security risk of not knowing what site you are connected to. Instead, it interprets that parameter as "show but don't let them modify the address," if I recall correctly. --Mr.98 (talk) 20:15, 19 August 2010 (UTC)

Right. I'm looking for the term for an ad with "show but don't let them modify the address". I used the term "address bar" to mean you could modify. There was one method that lets there be a toolbar, the other type. That would have been a simpler way to say it than "back button, forward button, etc." so that first version would be "without a toolbar". It still doesn't say what the different versions are called.Vchimpanzee · talk · contributions · 20:36, 19 August 2010 (UTC)

Firefox calls this the "menubar" and the bar with the "forward/back" buttons the "navigation bar". Firefox also has a Bookmarks toolbar, a Status Bar, and other addons can add their own "bar". Javascript can enable or disable any of these, if you permit it. If you want to preclude Javascript from affecting these, you can use Firefox's about:config interface to control Javascript access (described in detail at Developer.Mozilla.org). There is also a "standard" menu that lets you configure some, but not all, options for JavaScript permissions. Nimur (talk) 23:06, 19 August 2010 (UTC)

If you're just looking for a term, I doubt there is one for that specific thing. It's just a popup window, and if you want to say it lacks a back button, well, you just say that. --Mr.98 (talk) 16:19, 20 August 2010 (UTC)

Computer Tech Associate

Hi. What kind of knowledge should a Computer Tech Associate have, what are the major responsibilities of this position, and what qualifications (if any) are expected? Thanks. ~AH1^(TCU) 18:45, 19 August 2010 (UTC)

It depends entirely on the job. "Computer Tech Associate" could be anything from a salesman at a computer store (who only needs to know how to get people to fork over cash) to a networking assistant (who only needs to know how to keep the cables untangled) to a computer repair assistant (who only needs to know how to fdisk-format-reinstall) to a computer electronics tech (who only needs to know how to use a grounding strap when swapping out components). You need to ask whomever is hiring a Computer Tech Associate as it is a very general term, like medical assistant or construction assistant. The specific job creates the qualifications and expectations. -- kainaw™ 19:43, 19 August 2010 (UTC)

Locating mobile phones internationally

Hi. Say you're in the UK, and you dial a UK mobile number, and that phone happens to be in another country. What, in simple terms, are the steps that enable the network to locate that phone, given that (I assume) the number you dialled is not guaranteed to be globally unique.

The phone number is globally unique. All numbers issued in country XYZ are unique within XYZ and there is an implied country code prefixed to it. So UK phone 07777-777777 has the unique global number +44-7777-777777. Whilst some other countries "7777-777777" will become (say) +123-7777-777777. I don't KNOW how it works, but I do know that turning your phone on in another country "registers" it with that foreign network. I imagine that that netwrok lets the "UK" know that the relevant phone number in now in the particular country. -- SGBailey (talk) 22:38, 19 August 2010 (UTC)

The number is globally unique; the full number is +44 7xxxxxxxxx, and it's the same number regardless of where the phone roams. Calling a UK mobile that's roaming in Darkest Peru entails calling the same number as you'd call if it was in the next room. The second part of your question is routing. Phones (strictly SIMs) are identified by their IMSI codes. Say you turn on a UK Vodafone mobile in Darkest Peru. It searches for all the available towers, hoping one is Vodafone UK. It doesn't find one, so it connects to anything, say a Claro Peru one. This handshake exchanges the SIM's MCC and MNC codes, 234 and 15 respectively, which identify it as a Vodafone UK. The Claro central office connects to the Vodafone UK central office and verifies that Vodafone will accept payment on this SIM (big telco providers have direct relationships with one another, smaller ones may use a big one as an intermediary). Vodafone confirms this, and remembers that the mobile is in Claro Peru's territory. So if someone in the UK phones that 07xxxxxxxxx number, Vodafone knows to route the call to Claro. Things are simpler if the phone, in Peru, makes a call - Claro routes the call as it would one of its own, but it sends the billing transaction to Vodafone. -- Finlay McWalter ☻ Talk 22:49, 19 August 2010 (UTC)

One thing that doesn't seem to be implemented by the GSM handshake is a a way to prioritise non-home network selection. So if that phone, turned on in Peru, can't see a Vodafone connection, but seeing towers run by Claro, Avanza, and Movistar, it will pick whichever it likes (often it gives the user the choice). If Vodafone has a deal with Avanza that makes the calls cheaper, that doesn't affect the handshake. In this circumstance I've received a text message from my home network saying "you could get cheaper calls if you connected to Avanza instead", but it's down to me to do it manually. -- Finlay McWalter ☻ Talk 22:56, 19 August 2010 (UTC)

To clarify one thing that may not have been obvious from FW's answer. If someone calls you while roaming, the call will always go thorough your home operator (at least AFAIK), even if it's from someone sitting right next to you. This isn't really that surprising, when someone calls you, your number is a UK one, specifically a UK Vodafone one so the network of the person calling you connect it to Vodafone UK, who then have to send it back to you since they know you're there. This is I think one of the key reasons why receiving a call is usually rather expensive and in fact receiving a call from someone in the UK is often the same price, perhaps even cheaper then receiving a call from someone where you're actually located. (Calling someone locally is often far cheaper, also for the caller of course.)

In theory with smart IP networks, it wouldn't be that hard (relatively speaking) for the initial connection to go thorough Vodafone UK, but then Vodafone UK tells the network of the calling party to route it to the network the phone is currently connected to (although there's need to be some way to handle voicemail and stuff like that) but I don't know if this is implemented if at all (it may be for networks run by the same parent company particularly if in a similar geographical location, I know for Vodafone NZ you could use your phone in Australia and only pay normal Vodafone NZ local rates IIRC, you didn't even need to register for roaming which you normally had/have to do).

BTW, while FW is right I think about the lack of prioritisation, that's I think only a problem if your network actually has a deal with the other networks. If there are 3 networks where you're located, but your network only has a deal with one, the other 2 networks which just tell you to bugger off when you try to connect to them (well it will probably say you can connect to me but only for emergency calls). (Or if it does connect, you'll see the emergency calls only and hopefully try a different one.) So at worst it may slow down getting a network.

Nil Einne (talk) 00:14, 20 August 2010 (UTC)

The mobile operators mostly have little financial incentive to implement smart routing (in practice I think all the CO equipment is quite capable of it, if configured to do so) - they like all that lovely roaming money they get, from temporary customers to don't know, and mostly can't shop around. The EU directive capping inter-member roaming charges (here) may incentivize them to do it (although they're still getting 37p a minute, so it's not that much of an incentive). It's quite possible that the EU will eventually want to abolish inter-member roaming fees altogether (it's really quite a marked obstacle to a single market) and you can bet the operators will route traffic very efficiently in that event. -- Finlay McWalter ☻ Talk 00:38, 20 August 2010 (UTC)

It's worth remembering of course it's not just the mobile operators that need to cooperate for this but other telcos as well. If someone in Peru calls you from a landline in Peru on your Vodafone UK mobile, then the Peruvian telco needs to have some sort of smart routing system so that's capable of learning it should route to the Peruvian mobile operator who's network your using rather then to the UK. Of course in general the mobile companies and the other telcos are related. Nil Einne (talk) 07:10, 22 August 2010 (UTC)

• Thanks for all the answers! When I said "not guaranteed to be globally unique" I meant "not guaranteed to be globally unique unless a country code (or some other relevant code) is appended". So, really is it just that if you don't append a country code then you're assumed to be calling a mobile issued in the same country that you're calling from, and the appropriate country code is transparently appended by the network to uniquify the number? —Preceding unsigned comment added by 86.184.25.4 (talk) 00:53, 20 August 2010 (UTC)

I think that, if you fail to add a country code, then the assumed country is the one that the phone is registered in. i.e. if you're in Peru and call 07777 777 777 on a UK Vodafone phone, then I believe you get a UK number. Open to correction, though.--Phil Holmes (talk) 08:02, 20 August 2010 (UTC)

I wonder if this depends on the network you are using. Note the idea of transparently appending the country code is probably unnecessary anyway. If the local operator routes it locally, the country code is irrelevant. If it sends it to Vodafone UK, once it reaches Vodafone UK the country code is likely irrelevant. In any case, I would suspect most operators won't recommend it in case it doesn't do what you expect. Personally I never enter a stored number in my mobile without the country code. It seems pointless. Nil Einne (talk) 07:17, 22 August 2010 (UTC)

are laptop fans interchangeable?

For months now my laptop fan has ceased to work, i.e. there is no exhaust air coming out even when the laptop is at 80 C. I have been using a hack of an external fan + cooling pad, which sometimes keeps the internal temperatures at 40-50C. The CPU is often cooler than the motherboard air which I take to be a sign that the big laptop fan has failed and not the CPU heatsink fan.

Now, I haven't taken it apart to look at lint clogging, etc. I have already sprayed the outside of my laptop (and its vents) with compressed air. Is it likely that my fan has ceased to work completely, or will spraying my fan with compressed air free it up again? Also I can't find any laptop fans for my model in stock. How interchangeable are laptop fans? I kinda want to upgrade to an extra loud, extra powerful one anyway. John Riemann Soong (talk) 23:33, 19 August 2010 (UTC)

The fans are very often part of a fan unit, which includes a duct or heat-pipe, and you'd end up having to replace the whole thing. As such units are contorted to the weird spaces available, they're generally model-specific. I've never known dust etc. to foul a fan so completely that it doesn't work, just that it becomes noisy and inefficient. Note that your BIOS may have a screen that shows the fan's speed (or try Speedfan). -- Finlay McWalter ☻ Talk 23:43, 19 August 2010 (UTC)

On the Mac, iStat Pro can show fan speed, amongst other things such as temperatures. Chevymontecarlo 07:04, 20 August 2010 (UTC)

Certifications/ASP

First a background: I've not been working in the IT/programming industry for several years, although computer science was my major. I am currently in the process of looking for work here, but the economy stinks so companies don't want to hire people with very little experience. The ones that do mostly require some sort of certification, e.g., A+ certification. My questions:

1. How can I go about getting one of these certifications?
2. What's the best way to go about learning popular languages and frameworks like .NET and ASP (everyone seems to be looking to hire for these)?

I am willing to put up some money for the training, but I'd sure like to not have to spend more than 1 or 2 grand total. I live in the US. Magog the Ogre (talk) 23:59, 19 August 2010 (UTC)

Microsoft has some pretty good online training material for things like ASP.NET (some of which is free). Their info for training and certification is here (comparable things are run by Oracle, Redhat, Cisco etc.). Exams that go toward certification are generally administered by specialist testing companies (MS seems to use Prometric a lot), where you go to their testing centre (which is "local"). These tests aren't terribly cheap (MS ones in the US administered by Prometric seemed to cost $125 each); how many you need to take depends on the certification, but it seems to take several. That's the only cost you need to do; for many things they also sell self-study guides and of course (if a company with deep pockets is around to pay for it) optional training. -- Finlay McWalter ☻ Talk 00:55, 20 August 2010 (UTC)

And if you're wondering, the test is almost always entirely computer based. All the testing company does is verify your identity (so you haven't sent someone knowledgeable in to do the exam for you) and they watch that you don't cheat. For some certifications (like Cisco networking things) you really have to buy a simulator (as you obviously can't be experimenting on a room full of Cisco switches). -- Finlay McWalter ☻ Talk 00:59, 20 August 2010 (UTC)

August 20

Burning FLV straight to DVD

Hello! I've spent the better part of four hours split between today and yesterday trying to convert a Flash video file into a format that Windows Movie Maker would like so I could burn it to a DVD that would be readable by a standard DVD player. The problem was every time I tried either the Windows Movie Maker couldn't play the converted file, or VLC Player's converter or Mencoder (which use the same set of codecs, as I understand it) mangled the file one way or another. Needless to say, I'm fed up trying to jump from one encoding to another and was wondering if anyone knows a way to burn FLV files to DVD-player-readable DVDs with as little effort as possible. A quick Google search suggests some program called "FlashOnTV," but I'm weary of freeware programs I've never heard of, that they might contain some malicious code or won't do the job right, given the hard time I've had working with completely open-source alternatives. Suggestions? By the way, I'm using DVD+RWs, but I assume that these should work the same as DVD+Rs, with the rewritability as an extra. Much appreciated.--el Aprel (^facta-_facienda) 05:12, 20 August 2010 (UTC)

I use a shareware tool called ConvertXtoDVD, it's always worked for me. Sandman30s (talk) 08:52, 20 August 2010 (UTC)

For converting flv to something Windows Movie Maker will likely understand you can use avidemux. Load the flv into it, set video option to "MPEG-1", audio to "mp3", and format to "avi", then File -> Save -> Save video, and it will encode it. 1230049-0012394-C (talk) 13:39, 20 August 2010 (UTC)

Aaah, thank you! Avidemux has to be the easiest encoder/decoder I've ever set eyes on. It performed much more reliable conversions than what I was getting with other software. I will have a look at CovertXtoDVD too, which probably saves time without an intermediate format. Thanks for the help.--el Aprel (^facta-_facienda) 23:05, 20 August 2010 (UTC)

Flickr

How do I download a Flickr movie? I know how to download a Flickr picture (i.e. jpg). I use Microsoft Vista.--Doug Coldwell ^talk 12:14, 20 August 2010 (UTC)

VideoDownloadHelper addon for Firefox can download them 1230049-0012394-C (talk) 13:26, 20 August 2010 (UTC)

I don't believe I have Firefox. Do I have to download it first? Will it work on Vista?--Doug Coldwell ^talk 14:31, 20 August 2010 (UTC)

Yes you will need to. Yes it will. If you are still using IE, FF will make you happy. -- Finlay McWalter ☻ Talk 15:02, 20 August 2010 (UTC)

Downloading video from Flickr is (1) difficult, but (2) not impossible. According to Flickr, this is against the rules; users "may embed your video in other web pages, provided they have permission, but can’t “download” them. Flickr uses a weak version of digital rights management by hiding the video data behind a server-side Flash application. For example, this video can be streamed and the complete data is downloaded to your computer, but "stays" inside the Flash framework. You will need a third-party program, like VideoDownloadHelper to intercept the video data as it transits from the Flickr server to your Adobe Flash player in your web-browser (or the straw-man Flash-player that VDH emulates internally). Other programs exist that can perform this function; or if you are a very technical person, you can intercept the packets and reconstruct the data yourself. But ultimately, the reason this is (1) "difficult" is because Flickr is trying to prevent you from doing it. In the future, it may be (2) "impossible" - if Flickr changes its video-system and strongly encrypts its data transfer, it will be impossible to play the video-data in "untrusted" video players (even if you manage to intercept and download it). My recommendation is do not use Flickr - or Youtube - or any other web site - that asks you to sign away the rights to your own content. Host your own photos, videos, and data on your own servers - it is not very difficult to learn how to do. I realize that this sort of runs against the grain of the "web 2.0" movement - but it is the most sustainable way to re-democratize the internet. Nimur (talk) 17:48, 20 August 2010 (UTC)

Amen, Nimur!--el Aprel (^facta-_facienda) 23:07, 20 August 2010 (UTC)

64 bit

A have a few questions about 64-bit. Can you install a 32-bit OS on a 64-bit computer? When a program has both 32-bit and 64-bit versions, what is the actual difference between them? Why is 64-bit necessary, is it really impossible to get more than 4 GB of ram on a 32-bit system? 82.44.54.4 (talk) 14:51, 20 August 2010 (UTC)

For both Intel and SPARC then yes, you can install a 32 bit OS on a system running a CPU; I don't know about other architectures. A 64 bit OS allows native 64 bit ints and 64 bit pointers (although a given 64 bit application may not necessarily be compiled that way). Yes, you can get more than 4GB of RAM on a 32-bit Intel system, using Physical Address Extension. -- Finlay McWalter ☻ Talk 15:01, 20 August 2010 (UTC)

Right - as Finlay has effectively pointed out, "64-bit computer" is not sufficient to identify the type of computer. Often, (nowadays in 2010), "64-bit" is synonymous with "x86_64", the 64-bit architecture used by Intel and AMD. For this specific type of system, 64-bit hardware is backwards compatible with all 32-bit software (though 32-bit software does not take full advantage of the new capabilities).

64-bit computers actually physically connect to more memory by providing more physical wires (and a set of instructions to directly load and store data using those wires). PAE, a specific way to extend 32-bit Intel computers' address space, is sort of like a compromise - PAE adds physically connected RAM, up to 36-bits worth. And it provides a way for a 32-bit system to compute and use 36-bit addresses, increasing the total number of memory locations that can be reached directly.

As far as "impossible" to extend beyond those limits: well, there is a fundamental rule in computer science that can be roughly summarized: all computers can emulate any behavior that any other computers can do. So, it is definitely possible to load an arbitrary quantity of RAM on a 32-bit platform (or even a 4-bit computer). But it won't be very fast! In a sense, a "hard disk drive" is a serially-accessible memory unit that can serially store "arbitrarily large" quantities of data - but it is not RAM in the literal sense, for exactly this reason. Though, technology exists to "emulate" random addressing on any type of storage-medium; and it is very common to pretend that the disk is RAM!. Nowadays, you can even buy RDMA servers, so you aren't limited by disk scan-speeds, and can add "arbitrarily large" quantities of network-attached RAM that is faster than disk access. But you still have to transfer the data from somewhere to the CPU; and the CPU needs to calculate where that data resides and how to get to it, (and handle the message-passing necessary to execute the transfers, and so on). Since such "emulation" means that there is not a direct connection between the CPU and any "random" address, it is slow to load data from these extended address spaces - and usually, computer designers don't like to spend a lot of time "emulating" basic operations like finding an address in memory. Most common operating systems will not permit you to address beyond the physical memory limitations of the CPU, because they know this is a dumb idea and will slow your computer programs to a grinding halt - but for some very specialized purposes, you can find extremely large-memory operating-systems that work on 32-bit CPUs. Nimur (talk) 17:38, 20 August 2010 (UTC)

Button on taskbar disappeared, the sequel

I forgot to ask about a way to videotape this. The computer has Firefox and is at a library.

This refers back to this question and this sequel.

This may not help anyone diagnose WHY the problem is happening, but today, when an ad was slow coming up, I switched to another window, and the button for the window I had been on disappeared. I was able to return to the window where I had been by clicking on the button for the window that I had gone to, and magically the button for the window whose button was gone appeared on the right, though it had started out on the left.

Last night, I had three buttons. I tried to switch to one of the buttons while an ad was very slow to come up, and then the button wasn't there, and Alt-Tab wouldn't make it come back. A few minutes earlier, one button disappeared, but by clicking on one of the buttons twice, the window came back and then the button did too.

On another occasion I had just two buttons and lost one.

I saved the addresses somewhere (but I don't know where) of the web sites that are particularly problematic today. This being at a library, I doubt they'll put in ad-blocking software. I think one of the addresses I was seeing at the bottom of the screen when an ad was slow to come up was cdn4.specificclick.net.Vchimpanzee · talk · contributions · 18:04, 20 August 2010 (UTC)

Without knowing the operating system of the computer and ALL of the software running on the computer, this cannot be diagnosed as a problem. It could be the design of whatever is running. Further, it would help if you used language that is common for others. You appear to be referring to the taskbar. When you say "button", most people will assume you are referring to a button somewhere on the screen, not a task on the taskbar. When you say that a button disappeared, you appear to mean that a task disappeared from the taskbar. Not all taskbars are the same. Some have grouping. When multiple tasks group together, they are shown as a single task. Others have hiding. Based on some rules, tasks that aren't being used will be hidden from the taskbar. So, without knowing exactly which taskbar you are using, it is hard to say that this is not how the taskbar is designed to operate. -- kainaw™ 18:46, 20 August 2010 (UTC)

Just be glad I figured out I could call it a taskbar. I used to refer to "the rectangles at the bottom of the screen". One day I listened to those who want me to Google for information and found the term "taskbar" and the term "button". It looks almost exactly like Taskbar#Screenshots but without the "e" and other symbols. When I say "button" I am referring to the blue rectangles, and they generally have a web site name, or sometimes just "Mozilla Firefox". One today said "Compose mail". There is no grouping taking place. These buttons are not supposed to disappear. And the tasks are not stopping. They are just hiding (and not because software was written for them to hide). This has only been going on for a couple of weeks.

Screenshots ... that gives me an idea. I don't know that anyone would videotape me working, but I could do a screenshot. Although I don't really know howVchimpanzee · talk · contributions · 19:18, 20 August 2010 (UTC)

VChimpanzee, based on the contents of your nearly weekly questions, you seem to be having extreme difficulty with basic operation of these computers. Either something is seriously faulty with the equipment, and you should report it to the owner/operator of the library-computers; or you should seriously consider an introductory class in operation of web-browsers. Check with your library to see if they offer a course in basic internet and computer use. If you are honestly unfamiliar with the basic terminology and operation, you might benefit a lot from a structured training course. We have a policy of assuming that you are posting your questions in good faith, but your descriptions and questions are really becoming quite inane - in this particular instance, it is not even clear what you are asking. There is a limit to how long these rants will be tolerated. Nimur (talk) 20:13, 20 August 2010 (UTC)

I am asking why these buttons are disappearing. I went to the trouble of learning what the terms were and even that wasn't enough for some people. I am not ranting. I am asking valid questions.Vchimpanzee · talk · contributions · 20:22, 20 August 2010 (UTC)

You will get better answers if your posts are formulated as questions and concisely summarize your problem. There is definite lack of questions, or even "?" punctuation in your posts. Nimur (talk) 21:28, 20 August 2010 (UTC)

You have been given two answers, both of which you appear to refuse to consider:

1. It is by design. The library has some modified taskbar program that purposely hides things. Without knowing what modifications are installed, we cannot make guesses about it.
2. There is a virus or malware on the computer. Without knowing specifically what is infecting the computer, we cannot make guesses about it.

Until you can definitely show that the library has not modified the operating system and that there is no infection on the computer, we cannot go any further. -- kainaw™ 15:26, 21 August 2010 (UTC)

If you're using Microsoft Windows 7; right-click the Windows button, and select Properties. Choose yhe Taskbar tab, and select Never Combine option in the Taskbar buttons: drop-down menu. This will stop multiple simultaneous windows of the same application from being grouped into the same task on the Taskbar. But be warned that depending on how many applications and how many windows of each you have open at the same time, this could clutter up your taskbar very quickly; if your taskbar overflows, excess tasks will be automatically hidden in a menu accessible by clicking the double-right-arrow-bracket button which will appear on the taskbar just before the system tray. You should also consider increasing the size of your taskbar to double-height or triple-height.

I agree with [User:Nimur|Nimur] though, in that you benefit greatly from structured training in basic computer and internet usage. As for going "to the trouble of learning what the terms were", IMHO, if you consider that troublesome, no offence but you probably shouldn't be operating a computer and/or accessing the Internet. In addition, the wording of your original post is much more closely resembles a rant than a question, and insuufficient details (operating-system, browser-application, etc.) have been provided. Rocketshiporion Sunday 22-August-2010, 12:50pm GMT

Registry access from a different OS

I have a computer which dual boots into Windows XP Home and Professional; or did before its Home edition died. It is still technically installed but impossible to boot into. What I need to know is, how can I access the registry of Windows XP Home from Windows XP Professional? Thanks. 97.125.84.72 (talk) 21:41, 20 August 2010 (UTC)

Assuming you can actually see the Windows XP Home installation files, you can load the registry hive. To do this you need to run the registry editor (regedit.exe) and click HKEY_LOCAL_MACHINE (because I assume that's what you want to edit given the problem with it not actually booting). Then from the file menu select "Load Hive" and navigate to the Windows\SYSTEM32\Config folder of your Windows XP Home machine (You have to click the key other Load Hive will be greyed out). Select the file you want to open depending on where in the registry you want to edit (SOFTWARE or SYSTEM probably?) and if I remember correctly it'll then ask you for a name to call this, you can call it anything you like, it's just for your reference and it'll appear mounted from that point. If you want to open another key just repeat the process. Do your editing and unload the Hive pretty the same way. Hope this helps!  ZX81  ^talk 22:10, 20 August 2010 (UTC)

Microsoft link about it is here (although they don't go into any great detail!)  ZX81  ^talk 22:12, 20 August 2010 (UTC)

There's a linux program that allows this too, although the name escapes me right now. Let me know if that would be helpful and I can find out the name for you. Shadowjams (talk) 02:58, 21 August 2010 (UTC)

Program to compare drives/folders

Let's say that I cloned a hard drive onto another drive, but I think something may have gone wrong, as the total space used, and total number of files are different now. Anyone know of a (free) program that can compare the two drives? Sort of like a duplicate file folder, only opposite (if that makes sense). Thanks. -71.62.210.112 (talk) 21:52, 20 August 2010 (UTC)

FastCopy can, just select the two drives and click "Listing" and it will output a list of any differences. It can copy any missed files so that the cloned drive contents are identical to the original, without having to recopy the entire drive again. ICE Mirror can also do this 82.44.54.4 (talk) 21:56, 20 August 2010 (UTC)

August 21

Would this power supply be sufficient for this build?

ASUS Crosshair IV Formula Motherboard - AMD 890FX, Socket AM3, ATX, DDR3, USB 3.0, RAID, SATA 6.0GB/s

AMD HDT90ZFBGRBOX Phenom II 1090T Black Edition Six Core Processor - 3.20GHz, 6MB Cache, 2000MHz (4000 MT/s) FSB, Retail, Socket AM3, Processor

Thermaltake CLP0564 Frio Dual 120mm Universal CPU Cooler - LGA1366, LGA1156, LGA775, AM3, AM2+, AM2

Western Digital WD10EARS Caviar Green Hard Drive - 1TB, 3.5", SATA 3G, 64MB Cache, GreenPower

XFX HD585XZABC Radeon HD 5850 Black Edition Video Card - 1GB GDDR5, PCI Express 2.0, CrossFireX, DirectX 11, HDMI, Dual DVI x2 Planning to crossfire.

Corsair CMT8GX3M4A1866C9 Domintor GT Dual Channel 8192MB PC15000 DDR3 Memory - 1866MHz, 4x2048MB, 9-9-9-24

Cooler Master RC-942-KKN1 HAF X ATX Full Tower Computer Case - ATX, 230mm Red LED Fan, USB 2.0/3.0, 9x Expansion Slots. *Supports XL-ATX, 4-way SLI and Quad Crossfire X

Would this power supply power this build? XFX 850W Black Edition Modular Power Supply - ATX, 80 Plus Silver, 135mm Fan, Single Rail, NVIDIA SLI, ATI CrossFire Ready

Any help would be much appreciated:) —Preceding unsigned comment added by 99.155.19.25 (talk) 00:45, 21 August 2010 (UTC)

You know Caviar Green drives are not good as boot drives right? You are spending quite a bit of money here, so might as well get a SSD. Get a Sandforce or Intel. If you insist on using HDD, at least get a F1 or something. 121.72.208.23 (talk) 02:42, 21 August 2010 (UTC)

OT, but my recommendation for SSDs applies equally whether you are buying a 6 core like OP or an el-cheapo 2 core Athlon X2 250 like me. It really does make a huge difference to the computer's responsiveness. 121.72.208.23 (talk) 02:49, 21 August 2010 (UTC)

want to edit the boot.ini

This is is my boot.ini on WinXP machine. I want to remove the OS selector window appearing each time I boot. There is only one OS currently. What should I edit out to do that?

[boot loader]
timeout=3
default=multi(0)disk(0)rdisk(0)partition(1)\WINDOWS
[operating systems]
multi(0)disk(0)rdisk(0)partition(1)\WINDOWS="Microsoft... 
c:\grldr="Start GRUB"

--117.204.83.220 (talk) 04:34, 21 August 2010 (UTC)

Remove the c:\grldr="Start GRUB" line and then boot from your Windows XP installation CD. Run the recovery console and type fixboot and press ENTER. Then type fixmbr and press ENTER. Besides changing boot.ini Linux also edits the MBR on your drive. So, simply changing the boot.ini file isn't enough.--Best Dog Ever (talk) 04:47, 21 August 2010 (UTC)

Umm, no. If there's a C:\grldr="Start GRUB" line present in boot.ini, then the MBR and boot sector have not been altered by Linux. If GRUB would have been installed to the MBR, there would be no need for the line in boot.ini, as GRUB would start immediately. The line in question is to allow the XP boot manager to pass control to GRUB (GRUB4DOS, in this particular instance). -- 78.43.71.155 (talk) 17:50, 21 August 2010 (UTC)

So, the last line could be safely removed? In case of boot failure a fixmbr would fix it? --117.204.86.159 (talk) 18:47, 21 August 2010 (UTC)

There simply will not be a case of boot failure by removing that line. -- 78.43.71.155 (talk) 19:52, 21 August 2010 (UTC)

True. I removed the last line and it now boots without the OS selection screen. Thanks. --117.204.84.201 (talk) 11:29, 22 August 2010 (UTC)

php functions

been searching for a php function that when supplied with an array key would return its current array position, i mean when keys are integers but not the same as the positions in the array. and also one that would set an array current position to the specified pos so when you do foreach for expample it would start right from there I also need only php-built in ones not written by yourself

thnx —Preceding unsigned comment added by 85.26.241.39 (talk) 06:59, 21 August 2010 (UTC)

Is array-search what you need? -- Finlay McWalter ☻ Talk 11:39, 21 August 2010 (UTC)

I don't think so — if I understand correctly (and man, it would help to give more concrete examples), he has an array like this:

array (
2 => apple,
4 => orange,
5 => grape);

And what he wants is to say "where is 4?" and it will say, "oh, 4 is in position #2 out of 3 in the array." I don't think there's a built-in function that can do that. You will either have to write one (which could be quite slow depending on how big your dataset is), or you will have to re-work your code so it doesn't require knowing that information. I suspect the latter because you can't start a foreach from an arbitrary position — you can't set the array pointer arbitrarily, you have to start from the beginning and advance it either with "each" or "next" statements.

The only way to do more or less what you want that I can see is to dump the keys into an array (array_keys), then use array_search on that array to find the position, and then just reference the original array by the key name. --Mr.98 (talk) 14:54, 21 August 2010 (UTC)

A short function that does what you want is here. But I remind you that you can't start a foreach arbitrarily — it always starts from the beginning. What you could do is extract the part of the array you want to traverse into a new array, so that the beginning is where you want it, I guess. All of this sounds very inefficient to me, though.

function key_pos($input_array, $key) {
	$key_array = array_keys($input_array);
	return array_search($key, $key_array);
}

--Mr.98 (talk) 15:10, 21 August 2010 (UTC)

And here is an example that integrates it with your traversing of the array (which can't be done with foreach):

$arr = array (2=>"apple", 4=>"orange", 5=>"banana", 10=>"grape");

$key_array = array_keys($arr);
$key_orange = array_search(4, $key_array);

for($i=$key_orange;$i<count($arr);$i++) {
	echo $key_array[$i]."=>".$arr[$key_array[$i]]."\n";
}

That will output "orange, banana, grape", skipping "apple". I don't know if this is faster than just iterating over the whole thing with a foreach and ignoring the values that come before your desired key. --Mr.98 (talk) 15:14, 21 August 2010 (UTC)

Ubuntu home directory and settings in kde

I just reinstalled ubuntu and I thought that copying over my previous home directory would restore my old settings. That doesn't seem to have happened at least with respect to kde. Are these settings stored somewhere else? —Preceding unsigned comment added by 166.137.142.134 (talk) 09:00, 21 August 2010 (UTC)

Are you sure its KDE not Gnome? Ubuntu uses Gnome by default (Kbuntu is a version of Ubuntu that uses KDE by default). KDE's configuration is stored in ~/.kde3 where ~/ is your home directory. Some programs hide files starting with a . by default. CS Miller (talk) 11:05, 21 August 2010 (UTC)

Exactly which settings are you missing? The KDM login theme or the user icon shown by KDM during login, maybe? -- 78.43.71.155 (talk) 18:33, 21 August 2010 (UTC)

Date modified in vista

Why is "date modified" not a default category to sort your files by in Windows Vista? It was in earlier versions of Windows. It's totally annoying that it isn't. You can still apply that category to a folder, it just takes longer.--Hsardoft (talk) 09:04, 21 August 2010 (UTC)

It depends what files Vista thinks are in the directory. If it believes there are photos, then it doesn't display Date Modified. If it thinks the contents are "All Items" then Date Modified is a categroy. You can get Data Modified to display in a folder by Right Click, Customize this folder and set it to All items. Annoys me too. --Phil Holmes (talk) 09:48, 21 August 2010 (UTC)

Fake email address

Doing a bit of reading about Phishing I know it is fairly straight forward to do a fake web page for login purposes, but is it also possible that a fake email address could be set up, I know a lot of companies use the standard firstname.lastname@companyname.com so what I was wondering could someone set up an email address using this format for instance joe.bloggs@bankofengland.co.uk, thanks Mo ainm~Talk 14:06, 21 August 2010 (UTC)

Email protocol allows you to use ANY email address when you send an email. It is very very very easy. In your email program, you will see a setting for "my email address". Set it to "president@whitehouse.gov" and send an email to your friends. There is no check to ensure that is your email. Spammers tend to use millions of email addresses and they randomly select one as the "from" and use that to send email to millions of others. Whomever has that from is then inundated with thousands of "failure" responses. -- kainaw™ 15:16, 21 August 2010 (UTC)

To clarify what Kainaw said - the From: and Reply-To: fields in an email address are about as reliable as the return-to address on the outside of a paper envelope - the sender can put on whatever they want.

If you want to setup a fake receiving email address it is just as easy as setting up a fake web site.

To set up a site, real or fake you -

• Request a static IP number from an ISP, you have no control over the IP number, as it will be allocated from your ISP's pool.
• Request a DNS name from a registrar. This gets you something like .example.com. You have full choice of this, except some TLD are restricted, for example .gov and .mil are only allowed for use by the US government.

What you do with the domain is up to yourself, however you would normally -

• Set up a computer with that the IP number, either at home or in a colocation centre.
• Install a DNS server on the computer, have the registrar delegate all queries for .example.com to your computer.
• Set up the primary name of the computer as www.example.com.
• In your DNS server, set up an Address alias smtp.example.com to your computer; it is now known as "smtp.example.com" as well.
• In your DNS server, set up an MX DNS record (Mail eXchange), this is used for delivering email to @example.com, point it at smtp.example.com
• Set up a mail server and www server.

This is what you do for a legitimate server. Since you are in full control of all addresses under the .example.com, and domains are resolved right-to-left, you can you can set up a fake site at whitehouse.gov.example.com. To do this you would -

• In your DNS server, set up an Address alias www.whitehouse.gov.example.com, aliasing it to www.example.com
• In your DNS server, set up an MX DNS record @whitehouse.gov.example.com, pointing it to smtp.example.com
• Modify the www and mail server configurations so they will accept queries to whitwehouse.gov.example.com as well as the primary ones set up above

You can now send and receive email from barack.obama@whitehouse.gov.example.com which has nothing to do with barack.obama@whitehouse.gov

Note that this is fairly easy to do, at technical level.

However, impersonating Barack Obama might be illegal, and is likely to get you extradited to the US.

CS Miller (talk) 15:52, 21 August 2010 (UTC)

Thats great thanks so even if the email comes from what looks like, in your case Csmiller, Barack Obama, just because it follows the correct format it could still be a fake address, thats exactly what I was wondering. Follow on question say I set up the email address barack.obama@whitehouse.gov and their was a legitimate email address for the American president using the same, when I typed in the address who would get the email? The fake President or Real? Mo ainm~Talk 15:59, 21 August 2010 (UTC)

The anatomy of an email address:

username @ subsite  .   site  .  ext
     |       |           |        \__ Top level
     |       |            \
     |        \            \_________ Second tier
     |         \
     |          \____________________ Third tier
     |
     \________________________________ Username

In order to decide where an email goes, the url is parsed from right to left; and as CSMiller has explained, whoever controls any tier has total control of the names of the subtiers from that point on. So, whitehouse.gov is controlled by the government; but whitehouse.gov.nimur.com is controlled by whoever controls nimur.com. The parse-order precedence is right-to-left; so if you want to guarantee identity, you need to make sure that the top-most (right-most) tiers are trusted (i.e., that you are sure they are who they say they are). Nimur (talk) 16:09, 21 August 2010 (UTC)

You can't "Set up" an account that is exactly "barack.obama@whitehouse.gov" because you don't control the server "whitehouse.gov". You can send emails with forged "From" addresses. If someone replies to the forged email, they'll send an email to whatever the return address is. This is exactly as if you wrote "B. Obama, 1600 Pennsylvania Avenue, Washington, D.C." in the upper left hand corner of an envelope. The person who got the envelope might be fooled into thinking it was from the president, but if they wrote back to that address it would go to the white house, not to the prankster who wrote the letter. APL (talk) 05:47, 22 August 2010 (UTC)

Plain old SMTP basically doesn't care what you claim to be sending it from. I remember back in the early 2000s when the UC Berkeley SMTP server was basically unsecured in this way, and you could set up your e-mail program with any "From" address you wanted, and it would send just like any other, as long as you were on the campus network. (You couldn't receive mail arbitrarily, but you could send it.) At some point I am pretty sure they switched to requiring authentication, which cuts down on that sort of thing a bit. --Mr.98 (talk) 22:12, 21 August 2010 (UTC)

Ipone 4 Apps

Is it true that if I were to purchase an Iphone4 Unlocked PAYG, I would be able to access less apps than I would on a contract phone? —Preceding unsigned comment added by 85.211.141.84 (talk) 14:41, 21 August 2010 (UTC)

The purpose of unlocking a phone is so you can access apps that would otherwise be locked out...so I'd say the answer is no.Smallman12q (talk) 01:50, 22 August 2010 (UTC)

Malware through video codec?

Is it currently possible to be infected with malware through a video codec? --Belchman (talk) 15:03, 21 August 2010 (UTC)

From this link in 2008 it appears it is. Mo ainm~Talk 15:07, 21 August 2010 (UTC)

Not really... that link just says that someone may send you a trojan whose filename appears to be a video codec - which isn't anything new. --Belchman (talk) 16:39, 21 August 2010 (UTC)

Yes...its possible. A Video codec is nothing more than a library (computing)/API. Your question isn't specific in that the video codec is delivering the malware or if the contents processed through the video codec are delivering it...but its possible. There are plenty of trojan codecs...and codecs can be exploited via content processed through them via buffer flow exploitations which allow malicious code to be executed such as this one with Xvid and this one with MP3s. Hope this answers your question.Smallman12q (talk) 23:05, 21 August 2010 (UTC)

The way I wrote my question makes it almost impossible to understand. My apologies. I meant that if it is possible to get malware by watching a video you just downloaded through a torrent, p2p or whatever. Thank you :) --Belchman (talk) 00:54, 22 August 2010 (UTC)

Depends on the source...though most online web players/hosts such as hulu, megavideo, youtube, etc. are virus free. For actual p2p downloads...it could happen if you download from a malicious source.Smallman12q (talk) 01:48, 22 August 2010 (UTC)

Student laptop webcam surveillance

What steps can students take to avoid webcam surveillance of the sort described in Blake J. Robbins v. Lower Merion School District?
—Wavelength (talk) 15:17, 21 August 2010 (UTC)

Put masking tape over the camera lens ;D --71.141.97.250 (talk) 16:14, 21 August 2010 (UTC)

Taping over the webcam is mentioned here, on page 41.—Wavelength (talk) 19:32, 21 August 2010 (UTC)

Own and operate your own equipment, and only install trusted system-software. Nimur (talk) 16:24, 21 August 2010 (UTC)

Atleast 55,603 photographs; there would probably be around 1,390 images of students in a state of undress in that lot!! What were they trying to do - start a kiddy porn shop? And how can anyone be absolutely certain that none of the photographs snapped of students in various states of undress were not sold to perverts and pedophiles? If pictures of even one student was sold to even one pedophile, the student could be at risk from that pedophile!! One would wonder how this could happen in America. Rocketshiporion

Ignore my earlier outburst - here's what to do on a Windows computer to disable your webcam, so that it cannot be activated by software.

1. Step 1: Click the Windows button (or press the Start button on your keyboard), then right-click Computer.
2. Step 2: A menu will open - select Manage on this menu. If you are not logged in as the Administrator, you may be requested for a password or for confirmation - type in the password then press enter, or provide confirmation.
3. Step 3: The Computer Management Console window will open. Click Device Manager (located on the menu on the left under System Tools).
4. Step 4: Locate and expand the Imaging Devices hierarchy. The webcam will appear here under the name Integrated Webcam, USB Video Device or something else similar.
5. Step 5: Right-click the name of the webcam, and select Properties from the menu which appears.
6. Step 6: The Properties box will appear. Select the Driver tab, and click the Disable Device button. If a passsword or confirmation is requested, type in the password and press Enter, or provide confirmation.
7. Step 7: Click OK to close the Properties box. Important: Do not click Cancel, as this will undo your changes.
8. Step 8: At the top-left corner of the Computer Management Console window, click File then select Exit from the menu which appears.
9. Note: If you would like to uninstall your webcam instead of disabling it, in Step 7, click the Uninstall button instead of the Disable Device button. Important: If you uninstall your webcam instead of disabling it, you will have to scan for hardware changes then manually reinstall the webcam's driver(s), if you should ever want to use the webcam again in future.

Rocketshiporion Sunday 22-August-2010, 12:48am GMT

Doubling up router cables

I have a router with four RJ45 sockets on the back. Is there any way to connect more than four devices to the router by cable, or do I need a bigger router with more sockets? 86.147.153.107 (talk) 17:41, 21 August 2010 (UTC)

Add another router or hub to it; use a normal or cross piece of Cat5 RJ45 cable to connect it to your main router. NB, what is normally called a 'router' for home use has a 4-port ethernet hub, a WiFi access point and a ADSL modem built in. The second router does not need WiFi or ADSL. Most cable-modems' routers are rated at 100Mbit/s; if you often transfer data between two local computers you should get a 1gigabit/sec ethernet router and connect as many of your computers as possible to it. CS Miller (talk) 18:01, 21 August 2010 (UTC)

A switch will do (adding another router doesn't really make sense, that'd be overkill, and hubs are basically outdated devices, switches are what is used these days). Think of it as an extension cord, just for network devices rather than for power. -- 78.43.71.155 (talk) 18:21, 21 August 2010 (UTC)

See Network switch. Equisetum (talk | email | contributions) 21:32, 21 August 2010 (UTC)

August 22

Dual-Domain (Hard Disk Drives)

Hi.

   Why are many modern SAS HDDs dual-ported; what precisely is the meaning and function of dual-domain in this regard, and what are the differences and advantages/disadvantages between dual-domain and single-domain?

   Thank you in advance in all respondents.Rocketshiporion Sunday 8-August-2010, 12:34am GMT

A dual-domain drive can be connected to two host bus controllers (in a coherent fashion, in the same fabric, not just willy nilly). If either dies, traffic can failover to the alternate path through the second HBA. This way no single HBA is a single point of failure - if one dies, the traffic fails over. The operator can decable the drives from the bad HBA, replace it (assuming it's hotplug too, which would only make sense), recable in the replacement, and the system should go back to redundant operation. Fiber Channel already does this. -- Finlay McWalter ☻ Talk 01:52, 22 August 2010 (UTC)

Exact upload date for a file?

Hello. Is there a reliable way to upload a file (of any kind, a document, an executable etc.) somewhere on the Internet, and know the exact date such file was uploaded? The idea is that anyone could prove reliably and easily that the file existed and was uploaded at an exact moment in time. Is there a website that specializes in this sort of thing? Or is there at least some website (file host, etc.) that happens to do this in a clear and visible way? Or is there a way to do this other than with a website, like FTP or something? I have no idea! Sorry if my question sounds dumb... Thanks in advance. -.-; Kreachure (talk) 00:34, 22 August 2010 (UTC)

Only the webmaster of the server to which the file was uploaded could determine the exact date...unless details of the file posting time is given.Smallman12q (talk) 01:46, 22 August 2010 (UTC)

Most FTP services allow the user to see the standard file date information which includes file creation time. It is based on the server's internal clock, which may very well be off my not only minutes, but many years. Therefore, knowing the exact upload date requires checking the file date and knowing how off the server's time was when the file was uploaded. -- kainaw™ 01:48, 22 August 2010 (UTC)

If you are interested in a method to later prove to the world that your document existed at a given date, you may be interested in the ANSI ASC X9.95 Standard for trusted timestamps. -- Tom N (tcncv) talk/contrib 03:27, 22 August 2010 (UTC)

Yup, timestamps were the thing I was looking for. I decided to use a website (Copyclaim) that generates and certifies a timestamp with several hash functions, so that you can confirm the time of submission with either the generated hash or the file itself. Thanks! :) Kreachure (talk) 03:42, 22 August 2010 (UTC)

Copyclaim looks legitimate enough, but they have no visible means of support and might disappear at any time, taking your means of verification with them. A possibly better approach is to make a short text document containing the same information you would send to Copyclaim, and then post that document, or a hash of it, to Usenet. Of course, you could do both. -- BenRG (talk) 07:59, 22 August 2010 (UTC)

We should also make clear that "proving" the original date is different in different communities. To prove authenticity to a computer geek, you can provide technically accurate authenticated timestamps and cryptographic hashes. This is probably the best way to guarantee the content, because it is cryptographically strong. However, proving authenticity in this manner is not pin-for-pin compatible with "proving" in a legal setting. It is more likely that a court would accept a notarized letter or a sworn statement from an attorney, rather than any kind of technical validation of the original date. (This method has flaws, but it will probably be more widely accepted if you have to prove authenticity in court!) The best way to prove original date of creation therefore depends on your purpose. Nimur (talk) 16:07, 22 August 2010 (UTC)

Building a desktop PC - am I missing anything?

Hi everyone. I last built a PC in 2002, so things have changed a bit and I'm not 100% confident I still know what's what anymore. Could you please look at this parts list and let me know if I left out any key components or if something in here is grossly inadequate/inappropriate? The objective is to build a mid/upper-mid range desktop that I can expand upon in the coming years...

• CPU - AMD Phenom II X4 945 3.0GHz 6MB L3 Cache AM3
• Video Card - Sapphire 5770 1G 850MHz 4800MHz 1GB 128-bit GDDR5
• Mobo - GIGABYTE GA-MA770T-UD3P Socket AM3 AMD 770 ATX
• HD - Hitachi 1TB 32MB SATA 3.0Gb/s 3.5
• RAM - 2(or 3) x Kingston DDR3 1333 2GB
• PSU - CoolerMaster GX 750W RS-750-ACAA-E3

I figure network and sound cards are fully on-board these days (yes, it's been that long since I last built a PC!). I was always annoyed by these questions before, but now I find myself forced to ask one. So, thank you for your patience. 61.189.63.176 (talk) 03:51, 22 August 2010 (UTC)

• You will also need a case, a CPU fan, and you will also want some kind of DVD/CD drive/burner. And also the external stuff and software. (mouse monitor keyboard, operating system, power cord) Graeme Bartlett (talk) 04:29, 22 August 2010 (UTC)

I guess that's my punishment for trying to be concise. Yes, I know that I need everything else you listed Graeme. I chose not to include them because they're assumed to be present (to me, at least!) and I didn't want to clutter up my list. Thank you for replying, though. 61.189.63.176 (talk) 04:50, 22 August 2010 (UTC)

I see that you're intending to use the Gigabyte GA-MA770T-UD3P motherboard. Other than the one x16 PCIe 2.0 slot (which you'll be using for your graphics card), this motherboard only has four x1 PCIe 2.0 and two 133MHz PCI slots, both of which are incompatible with the vast majority of present-day expansion cards. If you want a mid-range to high-end desktop which can expand upon in future, you should be looking at a motherboard with atleast; one x16 PCIe 2.0, two x8 PCIe 2.0 and one or two x4 PCIe 2.0 slots. You should also be looking at around 8GB to 12GB of RAM if you intend to run multiple simultaneous programs or memory-intensive programs (e.g. CAD, CAE, gaming, etc.) on the desktop. If you could specify your budget and what you are intending to use this desktop for, I might be able to recommend a more suitable set of components. Are you fixed on AMD, or would you consider Intel? It's less likely that there'll be problems (driver issues, compatibility, etc.) when the motherboard and other components are made by the same manufacturer. As someone who's currently building my own workstation computer, I am quite familiar with the present-day ranges of desktop components. Leave a note on my talk page. Rocketshiporion Sunday 22-August-2010, 6:10am GMT

Can you please enlighten me as to what common accessories uses PCIe x4 and x8 slots?121.74.179.226 (talk) 06:14, 22 August 2010 (UTC)

Realisticly compatibility problems when you buy decent quality components aren't really that common, there's no need to stick with one manufacturer. Nil Einne (talk) 07:00, 22 August 2010 (UTC)

Any reason for choosing Hitachi HDD? 121.74.179.226 (talk) 06:14, 22 August 2010 (UTC)

There's nothing wrong with Hitachi HDDs. I purchased one recently. It's quiet and the price was reasonable (as compared to more prestigious product lines like Western Digital's Caviar Black). People say that they're durable. They used to be branded with the IBM logo, but IBM sold it off to Hitachi a few years ago.--Best Dog Ever (talk) 08:55, 22 August 2010 (UTC)

Internet

My internet comes via a router with an ethernet cable, which is plugged directly into the computer. I have two computers and I used to sometimes transfer the cable to the other computer so it could have the internet, which needed the router to be unplugged and reset otherwise it wouldn't work on the second computer. However in the last week or so when I've done this, the internet has become unusable on both computers for up to three hours. I've tried resetting the router, resetting the computers, running all the troubbleshooting things on Windows which said the problem was "Local Area Connection 2 doesn't have a valid IP configuration". Why is this happening? There is obviously nothing wrong with either computer or the connections, since after three hours it comes back on its own, and it was working perfectly before I transferred the cable, and this method has worked for 2 years until now. 82.44.54.25 (talk) 10:27, 22 August 2010 (UTC)

Did you do anything to your Command prompt? If you release your IP there, you have to renew it. Hazard-SJ ^Talk 10:30, 22 August 2010 (UTC)

I didn't 82.44.54.25 (talk) 10:31, 22 August 2010 (UTC)

What do you think caused the problem? Hazard-SJ ^Talk 10:36, 22 August 2010 (UTC)

If the OP knew, would they be asking? sonia♫ 10:42, 22 August 2010 (UTC)

I said think. Additionally, it could have been caused by something they didn't expect to cause it. It could have also been something they tried, which didn't work well. I remember recently releasing my IP, and I couldn't use the Internet until I renew it. Hazard-SJ ^Talk 10:51, 22 August 2010 (UTC)

To be honest, I'm surprised you had to unplug and reset the router when you moved the cable. Most PCs recognise that a connection has been made through the Ethernet port and request a new IP address from the router using a mechanism known as DHCP. The router would normally respond with an IP address without any other action. I would first check whether you have your PCs set up to use DHCP - ask here if you don't know how to do this, and then I would suspect that the router has not been working properly for a while and is getting worse. --Phil Holmes (talk) 12:32, 22 August 2010 (UTC)

Maybe it's not really a router. --71.141.97.250 (talk) 21:11, 22 August 2010 (UTC)

Problems with Windows XP password

After returning from holiday,on switching on my computer,it asked for a password to enter Windows.As it has never done this before,I have absolutely no idea what this is.Trying 'Guest' and blank password tells there is a restriction on and to contact the system administrator.Trying 'Administrator' and a blank password tells me there are restrictions on this account.

Going into safe mode doesn't help as it still asks me for this password before I can do anything,as it does for 'Last Known Good'. The only thing that seems to work is leaving both fields blank-it then comes up with the message 'Loading personal settings..' before very quickly coming up with 'Logging off' and taking me straight back to the password field.

Any ideas as to how to get past this-nothing will come up even with Ctrl-Alt-Delete. The only buttons available are OK,Cancel(which is grayed out),Shut Down and Options.All that happens when you press options is the Shut Down button appears or disappears.

Many thanks... Lemon martini (talk) 14:15, 22 August 2010 (UTC)

You could down download the Ophcrack livecd on another computer and then try to get the password that way. You may have a virus in that you are being logged off as soon as you sign on...Smallman12q (talk) 14:58, 22 August 2010 (UTC)

What utf char ??

In China_Railways_DFH_shunting_locomotives#cite_note-6 the reference contains odd looking latin characters - what are they and how ??? (also I copied them from the title - since it's the reference title should I or should I not change them to standard latin chars ??) Sf5xeplus (talk) 16:14, 22 August 2010 (UTC)

They are fullwidth latin characters in the Halfwidth and Fullwidth Forms section (FFxx) of the Unicode Basic Multilingual Plane. -- Finlay McWalter ☻ Talk 16:44, 22 August 2010 (UTC)

Thank you once again for help with my utf problems.Sf5xeplus (talk) 17:51, 22 August 2010 (UTC)

You're welcome; they're interesting questions that I enjoy figuring out. As to whether you should change the text for the reference, I wouldn't bother - you've accurately characterised the cited reference, there's no need to "improve" on it. -- Finlay McWalter ☻ Talk 18:07, 22 August 2010 (UTC)

ImageMagick help!

I've been searching fruitlessly for a couple of hours now. Can someone please post some code that would resize and convert a whole bunch of JPG files in a folder to 800px width GIFs? Windows XP. FWIW I have IM 6.6.3Q16. As a bonus, how would I right-crop the input images by 120 pixels (equivalently crop the input images to 3336x2304) before processing the above. I'm at the point of tearing my hair out, I just can't find a clear example that indicates what I should do. The help files are also a bit cryptic. Thanks very much, I'll upload the fruits of my labour soon as I can do this process. Zunaid 16:45, 22 August 2010 (UTC)

Your first sentence isn't clear. Do you want to convert (say) 500 JPGs into 500 GIFs, or 500 JPGs into one animated GIF, or 500 JPGs into 50 animated GIFs, or what? -- Finlay McWalter ☻ Talk 16:51, 22 August 2010 (UTC)

500 JPGs into 500GIFs, I have a GIF animator program that will output an animated GIF for me afterwards, but I need to give it GIF files as an input. I'm sure ImageMagick could do this too, but I'm just tired and frustrated at going around in circles through web forums and help files. Zunaid 17:49, 22 August 2010 (UTC)

Resolved

or rather Template:Fuckit. I just found FastStone Photo Resizer which does the job brilliantly. Plus its GUI so much easier to just set up and use forst time. Will post the pic soon as it is ready. Zunaid 18:08, 22 August 2010 (UTC)

The fruits of my labour, behold the mighty Athlone Power Station cooling towers reduced to dust earlier today. Zunaid 18:59, 22 August 2010 (UTC)

It's very good. Remember to put a GFDL tag on it lest the Commons folks delete it. Personally I think the inter-frame delay is about twice what it should be. Also the program you've used has posterised the clouds - does it have a "dither" or "error dither" or "fs dither" option, which should remove those contours we see in the clouds? -- Finlay McWalter ☻ Talk 19:11, 22 August 2010 (UTC)

I hope you don't mind, I reduced the file size to just over 1mb and increased the frame rate a little http://i.imgur.com/OdAay.gif 82.44.54.25 (talk) 19:21, 22 August 2010 (UTC)

The ImageMagick command to take the raw JPGs and emit a downscaled, dithered, animated GIF should look something like this: convert -size 640x480 -delay 40 -dither FloydSteinberg -loop 0 DSC*.jpg athlone_cooling_towers_demolition_2010-08-22.gif      -- Finlay McWalter ☻ Talk 19:18, 22 August 2010 (UTC)

Unresolved

(Marking as unresolved again because we might just improve the current image with people's suggestions.) Finlay, that code doesn't work for me. It crunches for a LONG time but then produced just a 10 byte file. I did change it to -loop 1 and changed the filename filter to match my Canon images. Any other suggestions? Also, I need to crop the right 120 pixels or so, there's a street light on the right of the image that's distracting if left in. I'll also check if FastStone has options for dithering or such-like and see if I can improve it. Zunaid 20:38, 22 August 2010 (UTC)

search engine query cache

I am having extreme difficulty finding this. I know that all the big search engines cache popular queries. I am looking for some reference that backs the claim. I am not referring to the cache in your web browser. I am referring to caching popular queries on the search engine's server. For example, if 10% of all queries are for "Egg Recall", the search engine will process that query once and then store those results in cache. The following queries will pull from cache instead of searching through all the websites yet again. -- kainaw™ 17:12, 22 August 2010 (UTC)

It's not at all clear what Google caches, and I'd be reluctant to broadly say what "the search engine caches" or doesn't. From what we know about the structure of Google Search (which really isn't that much) it seems to be built on Google Web Server doing MapReduce querying BigTable built on Google File System. The GFS paper (Ghemawat et al.) says it does no data caching. The Wikipedia BigTable article is silent about data caching there too. If Google's front-end web service is structured broadly like Wikipedia's (which we can honestly only guess at) then that leaves three possible locations for caching: caching of complete web pages (which Wikipedia does with Squid), caching of precomputed HTML fragments (which Wikipedia does with memcached) and caching of raw query result [the output of the MapReduce call] (which Wikipedia doesn't cache, and for which I can think of even less reason for Google to cache). We know some parts of Google use memcached (it's part of AppEngine), but not whether Search does. I'm sure you're right, that they do cache a lot of stuff (they'd be mad not to, and they're not mad) but they're darned secretive about exactly where, and exactly what, they do cache. When the Google Dance still occurred (which it seems hasn't been for six or seven years) we could see that different web servers returned searches based on different images of the data (which seemed to be due to incremental replication, rather than caching) but since then (and surely several generations of infrastructure later), while searches are still inconsistent, they're inconsistently inconsistent. So I don't think anyone outside Google knows. -- Finlay McWalter ☻ Talk 18:28, 22 August 2010 (UTC)

Wiki link to odd page

Is their any way I can get this link to work properly as a reference - it seems to be bugging wikipedia..

"ERION Mantenimiento ferroviarro, S.A. , Presentation" (PDF). www.erion.es. Febuary 2008. {{cite web}}: Check date values in: |date= (help) the problem is this I think http://www.erion.es/2%20Presentacin%20de%20ERION%20Feb[1].2008.pdf and the ]

 http://www.erion.es/2%20Presentacin%20de%20ERION%20Feb[1].2008.pdf

..Sf5xeplus (talk) 19:11, 22 August 2010 (UTC)

The brackets are not among the allowed symbols in a wikipedia hyperlink listed here. You need to percent-encode them:

 http://www.erion.es/2%20Presentacin%20de%20ERION%20Feb%5B1%5D.2008.pdf

This works: "ERION Mantenimiento ferroviarro, S.A. , Presentation" (PDF). www.erion.es. Febuary 2008. {{cite web}}: Check date values in: |date= (help)

Thanks, just found the answer myself on http://meta.wikimedia.org/wiki/Help:URL .. using "%5d" and "%5b" for "]" , "["

Resolved

77.86.82.70 (talk) 20:14, 22 August 2010 (UTC)