Wikipedia:Reference desk/Computing

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December 15[edit]

Pc issue[edit]

hi.i have problem with my PC.My PC turn ON when i switch on the power at the power outlet. Already try some Basic troubleshooting steps but the problem still there. (talk) 01:07, 15 December 2014 (UTC)

If you shut it down from the Start button, does it stay off? If not, it may be something simple like your power button being stuck down or plugged into the wrong connector on the motherboard. Alternatively, your BIOS may be set to "Power on after power failure" - see, for example, this article from RS. Check your BIOS and see if this option is enabled, and disable it if so. Tevildo (talk) 01:24, 15 December 2014 (UTC)
1. What operating system do you have? (Windows 7, Windows 8, XP?)
2. What happens when you click on Start > Shutdown? Does the PC shut down and restart? Does the power light go off?
3. What sort of motherboard do you have? We'll be able to check what BIOS settings are available if you let us know.
Tevildo (talk) 12:44, 15 December 2014 (UTC)
  • The green wire of the PC is shortcut to ground
  • the front panel power switch is locked in position "on"
  • In the BIOS the "POWER STATE WHEN POWER LOST" setting is set in server mode "ALWAYS ON". Change this setting to "ALWAYS OFF" or "LAST STATE".
--Hans Haase (有问题吗) 19:39, 15 December 2014 (UTC)

can website block my ip address from accessing that website?[edit]

can website block my ip address from accessing that website? is that possible? Ram nareshji (talk) 07:39, 15 December 2014 (UTC)

Yes, that is a standard access control method. It can be done in the web server configuration or with a Firewall, etc. Why they would block it is another matter. You can sometimes get around such blocks with a proxy server or virtual private network. (talk) 08:15, 15 December 2014 (UTC)
Yes, indeed, but there are other ways in which your IP address can be blocked other than by the website itself. Thincat (talk) 08:54, 15 December 2014 (UTC)
Even wikipedia does it. Vespine (talk) 22:17, 15 December 2014 (UTC)

videos on computer[edit]

Hi, I've sometimes watched videos on my computer, including those I've downloaded onto my hard drive, and they play up in the same way as a CD, with some kind of "track skipping". That is, it gets jerky, and replays the same bit a few times, then gets going again. Why would a computer file be prone to any kind of track skipping? Surely it isn't the hard drive physically playing up (for if it was, there would be so much more wrong with my computer, I would think)? So assuming it's software, the problem makes no sense to me - I would expect freezing, crashing, or entirely random behaviour. Mimicking a physical malfunction seems strange. Any explanations?? Thanks in advance, IBE (talk) 08:55, 15 December 2014 (UTC)

When you play a video there's various things that have to happen between the hard drive and the screen. Depending on your computer, the video file will be loaded chunk by chunk into RAM or video memory. As it plays, the file then has to be decoded by the CPU or by a video decoder on the graphics card to form the picture you see on your screen.
Any one of those steps could cause stuttering. If your hard drive is busy, it might not provide the next chunk of the file in time for it to be decoded. Insufficient memory could cause the same problem, as the computer has to move other things back onto the disk to make space to load the new file. Or, if the resolution of the video is too high, the computer might simply not have the graphics-processing power to decode the frames at the speed it's trying to display them. If you know any information about your computer (how old it is, the amount of RAM memory, the type of processor, whether it has a graphics card), that might help to identify which component could be acting as the bottleneck. —Noiratsi (talk) 10:11, 15 December 2014 (UTC)
As Noiratsi says above, the computer has lots to do, so I find that it sometimes helps to close down all other applications and processes that I don't need. This might include agressive anti-virus software -- mine seems to disobey my explicit instructions to run in the background, and sometimes takes over processing time from what I want the CPU to concentrate on. Dbfirs 21:40, 15 December 2014 (UTC)
Audio data is written into a circular buffer in RAM and the sound card reads from that. If new data is not written in—because the CPU or hard drive is overloaded, for example—the sound card will wrap around the buffer and play the same short segment of audio repeatedly. Video also typically uses a circular buffer of 2 or 3 frames, but the frames are advanced by the same software that's drawing them, not by the video hardware, so if no new data is available the video will normally just freeze. -- BenRG (talk) 22:08, 15 December 2014 (UTC)

Lowest possible signal strength?[edit]

I just found out my phone has a way to display signal strength as a figure rather than bars. I know this won't improve anything but it's fun to see. When I have no signal here it shows my signal strength between -109 and -113. What's the lowest it can go where I actually have a valid signal for voice calls? Also, what's the very lowest it can go, for example if I sat inside a lead lined box underground in North Scotland. It's a GSM phone if that matters. (talk) 10:30, 15 December 2014 (UTC)

The unit is dBm. A minimum threshhold for a GSM call is around -105. You should read the article (I don't fully understand it), but to summarise, it seems the scale doesn't have a way to express theoretical zero—it goes all the way down to negative infinity. (Source and more figures: —Noiratsi (talk) 10:49, 15 December 2014 (UTC)
In the spirit of disclosure, we don't know that the display is showing data in units of dBm - although that is one common way to express such signal levels, there are many other methods and units. For example, received signal strength indication (as standardized by the IEEE 802.11 WiFi specifications) has arbitrary units; and it is permitted to vary between vendors and implementations; so there is no real way to relate its value to any physical parameter. Proprietary techniques for signal strength indicators proliferate widely in the consumer radio industry!
Nimur (talk) 17:00, 15 December 2014 (UTC)
To answer the theoretical part of the question, the thermal noise floor at 25°C with a 50 ohm load is -147 dBm/Hz, so for a single GSM channel with a bandwidth of 200 kHz, the noise floor is at -121 dBm. (Copper would be better than lead, incidentally - see Faraday cage.) Tevildo (talk) 01:35, 16 December 2014 (UTC)

What disasters were caused by bad programming, bad software development?[edit]

I see that software providers cover their back with a 'no guarantees' clause, but what has happened already due to buggy software?--Noopolo (talk) 19:05, 15 December 2014 (UTC) Divide by Zero error in a navy ship. Avono (talk) 19:34, 15 December 2014 (UTC)
Therac-25, Mars Climate Orbiter#Cause of failure. -- Finlay McWalterTalk 19:40, 15 December 2014 (UTC)
The 1990 AT&T Long Distance Network Collapse
Wikipedia has an interesting article List of software bugs. Since it only covers bugs that are notable in some way, a bunch of them might qualify as "disasters". APL (talk) 00:52, 16 December 2014 (UTC)

This list was constructed from articles posted in the Risks digest over the years. Not all of the items are examples of "buggy software"; see the table of descriptor codes near the top. -- (talk) 04:00, 16 December 2014 (UTC)

Which Linux distribution?[edit]

A friend of mine contacted me to say he has an old laptop running Windows 7 that he wishes to replace with Linux. I'm assuming the laptop is already several years old. I don't know its exact specs yet as I've not seen it yet. Which distribution should I use? The only distribution I have myself ever used is Fedora, and Red Hat before it became Fedora. My friend knows his way around Windows, although he has no training or experience in programming or system-level work like me. I'm assuming he has no previous experience of Linux, but should quickly pick it up once he sees it. JIP | Talk 19:34, 15 December 2014 (UTC)

Xubuntu -- Finlay McWalterTalk 19:41, 15 December 2014 (UTC)
Yes, or try to boot a 32 bit Linux Mint. When this live CD etablishes the desktop, it is possible to install it from desktop. --Hans Haase (有问题吗) 19:44, 15 December 2014 (UTC)
Yes, Linux Mint.--Aspro (talk) 10:54, 16 December 2014 (UTC)

What is Blipp?[edit]

An ad in my newspaper (which I get home delivered, so I'm talking about something I saw on paper, not online) tells me to Blipp. This seems to be connected to Blippar. Neither has a Wikipedia article unless this is somehow connected to Blip (website).— Vchimpanzee • talk • contributions • 19:57, 15 December 2014 (UTC)

g returned no:Stian Blipp or blippapp --Hans Haase (有问题吗) 20:16, 15 December 2014 (UTC)
I get something called "augmented reality advertising" but I'm not interested in the type of marketing-speak Wikipedia avoids.— Vchimpanzee • talk • contributions • 23:08, 15 December 2014 (UTC)

Videos for youtube[edit]

I am attempting to upload 6 different 40 minute albums up to youtube. My songs I made are around 12mb a song and I compiled them into on long mp3 file of the album just for youtube use and when I use Windows Movie Maker to take a picture/album cover and use that as the image for the youtube video the files end up being massive for some reason. All it is in the movie maker is the audio files aka mp3 files and they are about 50mb in total and the image is less than a mb in size. How can I Use my image and add the audio to it so it doesnt take up to much video space? The video files take for ever to finish and they are up to 350mb in size. — Preceding unsigned comment added by (talk) 23:00, 15 December 2014 (UTC)

December 16[edit]

Can I install two operating systems on one internal 3.5 inch hard disk[edit]

That's my question. Thanks --AboutFace 22 (talk) 01:14, 16 December 2014 (UTC)

That depends on the operating systems but it is possible. See boot loader. Dismas|(talk) 01:18, 16 December 2014 (UTC)

One OS is Windows Server 2008 and the other one, that I want to install also on the same disk is Ubuntu. --AboutFace 22 (talk) 01:53, 16 December 2014 (UTC)

Both O/S's would need to support the format used on the hard drive. And there might be other problems, like different O/S's using different paging space on the hard disk. I certainly wouldn't recommend it, but it might be possible. StuRat (talk) 02:38, 16 December 2014 (UTC)
This is certainly possible. You need to install the two operating systems to separate partitions within the single physical disk. Ubuntu has a good guide for going about this here. GoldenRing (talk) 03:28, 16 December 2014 (UTC)
Yes, Win first, then Ubu. But troubleshooting will be more complicated. Swapping 2 drives is less complicated. --Hans Haase (有问题吗) 12:12, 16 December 2014 (UTC)
I will second that. A second drive is well worth the money (and easy to instal, plus more storage, plus a convenient place to back up). <Linux plug>Also, you will then realize that of your precious time spent on maintenance and trouble shooting, is nearly all wasted on the drive hosting Microsoft. If window was released for the first time today, it wouldn’t stand a chance against the modern Linux family of no hassle distros. </Linux plug>--Aspro (talk) 22:58, 16 December 2014 (UTC)

Hosting English Wikipedia for a group of Users[edit]

I have installed MediaWiki 2 years ago.But since MediaWiki can't handle more than 1 GB(not sure) I changed to XOWA app.But using XOWA for a single user might be good but when it comes to a group of users I think MediaWiki might be more efficient since online wikipedia uses this software.Could you tell me are there any memory constraints for MediaWiki(asking whether it can handle a wikipedia dump of 10GB)?I once tried to install the dump by increasing the memory limit in php configuration file(apache too) in WAMP server but I think it can handle around 1GB as I tried but when it comes to the dump file(10GB) it usually gives some error.Since I couldn't get a lot(memory) from MediaWiki should I need to install any other software?Could anyone help me.JUSTIN JOHNS (talk) 03:52, 16 December 2014 (UTC)

What limit are you talking about, the media upload size limit?
Do you know about Wikipedia Zero and the project wiki on a stick or wikipedia offline? --Hans Haase (有问题吗) 12:16, 16 December 2014 (UTC)

@Hans Haase:No.I'm taking about the memory limit in MediaWiki for uploading(MAX_UPLOAD_SIZE in MediWiki).Also 'Wikipedia Zero' is an mobile application.I'm really asking about an software used in computer to allow a group of users access the wikipedia in a network.I have asked this question previously at :

Could you tell me is there any constraint in uploading a 10GB file(after uncompressing 40GB) into MediaWiki.Is there any other software that might be good to host an English Wikipedia for a group of users.I know about XOWA but using it individually might be good but when it comes to a group of users the addon(firefox) it provides doesn't work and the http connection is slow too.JUSTIN JOHNS (talk) 04:33, 17 December 2014 (UTC)

Trying to pronounce ð and θ[edit]

Hi there,
I've tried to pronounce those consonants,
I would like to hear comments about my pronunciation,
Beginning with accent, and particularly the pronunciation of the THs.
It should be "they think".
Another issue is that I noticed that most of the native-English speakers, put their tongue out.
What I do, is putting my edge of the tongue on my front teeth,so another part of the tongue is sliding out from the "teeth box".
It's like my tongue is in a C-like shape. Is it okay?
15:14, 16 December 2014 (UTC) — Preceding unsigned comment added by (talk)

If you were a computer, your post would have been justified here, otherwise, perhaps the Help desk would be the best place for it? --AboutFace 22 (talk) 15:44, 16 December 2014 (UTC)
You mean the Language Ref Desk, I assume  ? If so, I agree, unless they want an audio file or software tool to help them pronounce it (although they did mention C !). StuRat (talk) 16:40, 16 December 2014 (UTC)
The sound is faint for me, but I hear nothing wrong with it. —Tamfang (talk) 23:11, 16 December 2014 (UTC)

TV color adjustment[edit]

Faces on my TV have yellow patches on them. I have the following color controls for each color (R, G, B): brightness and contrast. So, since there's no option to turn yellow down, which sliders should I change ? It's an LCD TV with LED backlight, if that matters.


StuRat (talk) 17:32, 16 December 2014 (UTC)

The RGB color model is additive, and yellow is created by adding red and green - you should either decrease both, or increase the blue. AndyTheGrump (talk) 17:44, 16 December 2014 (UTC)
Since they are only yellow patches, not the whole image being too yellow, does that mean I should turn up the blue contrast and/or turn down the red and green contrast ? StuRat (talk) 17:53, 16 December 2014 (UTC)
Have you tried a test pattern? Many modern TVs have them built in, or you could pipe one in from a computer. I am suspicious that only patches of faces seem off. Other issue: what is the input signal? Broadcast HDTV? DVD? etc. It could be a problem with the input and not the display. The closest thing I can think of is when an old film noir movie has been poorly converted to DVD. When the MPEG encoding/compression isn't done right, you can clearly see clean squares of dark purple or maroon in what should be smooth deep shadows. Anyway, from your description, it's not clear to me that simple color adjustment will solve the problem, though it may help or at least make it less noticeable. SemanticMantis (talk) 18:35, 16 December 2014 (UTC)
The yellow patches aren't blocks, the seem to be areas of the face that maybe should be a bit more yellow, but are much more yellow instead. I turn up the blue contrast to max and turned down the red and green contrast to min. That certainly reduced the problem. BTW, this is broadcast HDTV (1080i). StuRat (talk) 22:03, 16 December 2014 (UTC)
I don't feel it's a good idea to make an adjustment to fix a specific problem; in my experience, that just creates another problem. Your problem might not even be in the color settings. I think a more "scientific" or "holistic" approach, for lack of a better word, works better over all, and there are a lot of web resources for "tv picture calibration". I was lucky with my current TV, a low-end HD LED model. Consumer Reports published a full set of picture settings (not only color) recommended for that model by their engineers/testers. I tried their recommendations and after two years I've been extremely happy with the results. ‑‑Mandruss  19:39, 16 December 2014 (UTC)
LOL, it sounds like it took two years to do the color calibration. StuRat (talk) 22:03, 16 December 2014 (UTC)
Eh? I don't know how long it took the engineers to determine the settings. It took me 5 minutes to set them and several months to decide that I was extremely happy. ‑‑Mandruss  22:08, 16 December 2014 (UTC)

Generating lists from Excel[edit]

I have something similar to the following table in Excel and I'm wondering if there is a way to generate lists from it in Excel or Word, such as, a list of Mr. Smith's math students, a list of Ms. Jones's science students, etc.

Name of student Class 1 Teacher 1 Class 2 Teacher 2 ...
Alison Math Mr. Smith Science Ms. Jones
Barry Gym Mr. Fisher Art Mr. Fraser
Charles Math Mr. Smith Art Mr. Fraser
Dawn Gym Mr. Fisher Art Mr. Fraser
Edward Gym Mr. Fisher Science Ms. Jones
Fred Drama Ms. Taylor Art Mr. Fraser
Greg Drama Ms. Taylor IT Ms. Carter
... ...

Carveroa14 (talk) 21:48, 16 December 2014 (UTC)

A simple way to do it in Excel is to use the Auto Filter function: filter "Teacher 1 = Mr. Smith" and "Class 1 = Math", then cut and paste the result into a new worksheet or into Word. --Canley (talk) 00:33, 17 December 2014 (UTC)
Yes and to export the sorted list should not be the problem. An other solution: Mark the whole table. In menue, select data, sort data and specifiy the sort order of the colmns. Copy an paste the result. If you do not want to change the excel file, close and don't save it. --Hans Haase (有问题吗) 16:31, 17 December 2014 (UTC)

Minimize Backtracking Algorithm[edit]

So today my teacher was talking about Depth-First Search and Breadth-First Search. He was saying how when finding the path you have to backtrack for DFS and go to the next available branch. When he finally had found the tree his tree seemed mangled and had multiple sections with non-sensical back-trackings (degree 1 nodes in the final tree). My question is "What is the easiest way to find a tree such that the minimal amount of traversing is required to pass through the tree. (explanation--when picking a new location how can I continue the line I am on without creating a dead end before passing over all nodes/vertices). Idk if this question has already been answered so if it has just post a link. Thnx -- Jetstream5500 (talk) 22:37, 16 December 2014 (UTC)

I think this is the "minimum leaf spanning tree" problem, which is NP complete since it has the Hamiltonian path as a special case. NP-complete problems aren't always intractable in practice, but this one doesn't even have a constant-factor approximation (i.e., a fast way to get within a factor of N of the minimum amount of backtracking). That probably means that a backtracking-minimized DFS would be much slower than an ordinary blind DFS. -- BenRG (talk) 00:24, 17 December 2014 (UTC)
Could you make an algorithm that could give not the correct answer but a possible answer that is 95% correct or would this still be difficult. In more general terms: Is there an algorithm that could make several spanning trees with 0 backtrackings and then somehow connect them to result in a fairly good answer.Jetstream5500 (talk) 03:15, 17 December 2014 (UTC)
Based on the info you've given, it sounds like you have no way of knowing when you are close to the target state. In that case there's really no efficient way to get there, other than an exhaustive search.
But, let's say you were solving a maze, and the desired state is being at the exit. In that case, you could use the Manhattan distance from your current location to the exit as an approximate measure of how close you are. Of course, it's not always correct, because there could be a wall in the way even though the distance is less. But this would allow you to prioritize search down branches with lower distances, and usually make your search more efficient.
I've also found that searching from both directions is more efficient yet. So, while you are branching from the maze entrance towards the exit, also branch from the exit towards the entrance, and when your two trees meet in the middle, that's your solution. StuRat (talk) 03:49, 17 December 2014 (UTC)
Could you break apart the maze anyway? When 2 graphs are connected by a bridge you can run the program on both sections thus starting in 4 locations right? This would be even quicker. --Jetstream5500 (talk) 04:48, 17 December 2014 (UTC)
Yes, but you'd need to know an intermediate state you will need to pass through (the "bridge") in order to break it down further. I was assuming the only two states which are known for sure are the start and end states (entrance to the maze and exit). Now, you could also have a system with multiple starting and ending states (entrances and exits, in the case of a maze). If the goal is to find the shortest path between any starting state and any ending state, then simultaneously building trees from each of those might also make sense. When the first tree from a starting state intercepts the first tree from an ending state, that's your solution.
Oh, and if you haven't already discussed pruning algorithms, the obvious one here is to prune off any branch that leads to a state that's already in that tree. In the case of a maze, that means we don't go back to any place in the maze we've already visited.
For a real-world example, lets say we are writing a program to find the shortest path between a start location and destination on a map (like Google Maps). We'd want to start a tree at each end, and also start trees at intermediate stops, if any. (In practice we'd completely solve one segment before starting the next, unless we are using some type of parallel computing architecture that would make solving all segments simultaneously faster.) We'd also want to weight each step by if it moves you closer or father from the goal state (location), and explore those nodes that get us closer first. As in the maze example, this is no longer guaranteed to find the best solution, because a route which initially takes you farther from the goal state may actually turn out to be the best (here perhaps that might mean driving to the nearest highway entrance, even though it's out of the way). Weightings could also be altered based on type of road, etc. StuRat (talk) 06:01, 17 December 2014 (UTC)
If you actually want to find a goal node quickly then A* search is often a good way to do it, but in this question there is no particular goal node. The goal is to explore the entire graph without backtracking. "Pruning off any branch that leads to a state that's already in that tree" is how DFS always works. I get the impression that you've never taken the standard algorithms course that Jetstream5500 is taking. -- BenRG (talk) 07:41, 17 December 2014 (UTC)
I just wasn't sure if he'd gotten to that part of the class yet. I took the class a while back, but didn't recall if they taught the pruning right up front, or first teach the difference between DFS and BFS and then add in pruning methods. StuRat (talk) 07:49, 17 December 2014 (UTC)
Im in a Discrete Math course in high school. Now I was wondering you can't find a path that minimizes back-tracking and you said this is similar to hamiltonian paths and cycles. What I was wondering is can you (like hamiltonian paths and cycles) determine if such a path through the nodes exists w/o actually knowing the exact path that would need to be taken. I like the idea of pruning and the above mentioned algorithms also. Also if you have 2 bridges to the same point you can eliminate a edge that passes between 'b' and 'c' if 'a' is part of graph 1 and 'b' 'c' are part of graph 2. Thank you for the responses. This problem makes a lot more sense now. Close approximations are the best you can do unless a new algorithm / idea comes along on hamiltonian paths/cyclesJetstream5500 (talk) 20:07, 17 December 2014 (UTC)
As far as a pair of bridges go, there are some different possible arrangements. One is if you can cross one or both bridges, as in two shores on opposite sides of a river with 2 bridges across it, where you start on one side of the river and must finish on th other. In this case the bridge just behaves like any other link between nodes. However, I assume you meant a case where there's an island in the river, and one bridge from the island to each shore, so that you must take each bridge exactly once to get from one shore to the other. In this case the problem breaks down to 3 distinct problems to be solved, optimizing the left shore navigation, island navigation, and right shore navigation.
BTW, edX offers an excellent class on Artificial Intelligence through the University of California at Berkley which covers this and much more, online, for free, the last time I checked. StuRat (talk) 10:46, 18 December 2014 (UTC)

December 17[edit]



Please don't SHOUT. Typically, a company will employ a firewall to limit internet access, either for security, to increase (perceived) productivity, or both. A firewall normally blocks most ports, allowing only connections to certain ports (and hence the associated services). What works for me is to go to the responsible system administrator and say "I need to access service X, please adapt the firewall". Success depends on the skill and workload of the admin, and your relative standing in the organisation. If some ports are open, you can always use a proxy and tunnel blocked services. The amount of technical skill needed for that varies, depending on what services are open and closed, and which services you want to use. You can use a virtual private network for this tunnelling, but in either case you need an unrestricted server somewhere for the final connection to the the internet. --Stephan Schulz (talk) 09:10, 17 December 2014 (UTC)
Note that any attempt to circumvent your employer's firewall is likely to result in disciplinary action, and could cost you your job. If you need access to a web-based resource to assist you in your work, ask your line manager to liaise with the IT dept. to add it to the whitelist of permitted sites. CS Miller (talk) 15:23, 17 December 2014 (UTC)

How to determine if I have new mail in Gmail[edit]

Yes, it lists the number of new messages and puts them in bold text. However, when I log in from a new location, it lists messages as new that were previously listed as new at the previous location. Is there a way to make it recognize that this mail is no longer new, since I already viewed the titles and decided not to read them ? StuRat (talk) 17:33, 17 December 2014 (UTC)

In my Gmail, messages stay new until I either read them or delete them, and this is the same wherever I access them from. Are you using POP? If so, there's a setting to mark as read on the server (settings -> Forwarding and POP/IMAP -> 2. When messages are accessed with POP -> Mark Gmail's copy as read). Dbfirs 10:39, 19 December 2014 (UTC)
Yep, that seems to have fixed it, thanks ! (I wonder how I got stuck with that odd setting.) StuRat (talk) 02:17, 20 December 2014 (UTC)

GPRS at 35 kbps (k not K)[edit]

If you have 35 kbps, what can you do with that? Can you at least send and receive emails?--Senteni (talk) 18:45, 17 December 2014 (UTC)

As long as the emails are plain text, yes. Full HTML might take a while, but it will probably work. KonveyorBelt 18:55, 17 December 2014 (UTC)
Your "(k not K)" comment confuses me. Either way, "k" or "K" both mean 1000. I'm guessing you meant "(b not B)", where "b" is a bit and "B" is a byte (typically 8 bits). So, 35 kbps is 35,000 bits per second. A character of text is typically encoded as an 8-bit byte, so that would mean you could send 35000/8 or 4375 characters per second. Allowing for some overhead, let's say 4000 characters per second. That's a lot of text. Possibly you could also send some sparse vector line drawings, like a map. Or you could even send some heavily compressed bitmap images, provided they had large areas of constant color, to make compression work best. Something like newspaper cartoons, perhaps.
There's also some possibility of sending animations, although they would be severely limited, and again use only sparse vector images or heavily compressed bitmaps. Let's say you send 10 frames per second, that means some 400 bytes per image. Each 2D vector on a 256x256 grid could be represented by 4 bytes, or 32 characters. Let's add 5th bit for the color of the line, allowing 256 different colors. That's 40 bits per line. So, you could have maybe 10 lines on the screen at a time. Maybe you could send an image of a rotating pyramid with that.
And many games don't require exchanging much info between players. Chess moves, for example, only require a few bytes of data each. Or each placement of a letter on a 19x19 Scrabble board requires only about 15 bits of data. So, entire game histories could be downloaded in a second. StuRat (talk) 19:12, 17 December 2014 (UTC)
yes, I meant kbits , not kbytes.Senteni (talk) 19:19, 17 December 2014 (UTC)
When I were a lad, we had 2400 bps - not "k", not "K", not anything. And that was perfectly OK for text and the occasional picture. Tevildo (talk) 21:50, 17 December 2014 (UTC)
Yes, I remember those days (in fact my dial-up phone line connection used to run around that speed until a few years ago), but we had problems when trying to download "big" files of perhaps 50KB. Dbfirs 23:44, 17 December 2014 (UTC)
You folks are too young. I remember when 1200 bps was a high-speed modem, normal ones being only 300 bps. And then there was 134.5 bps... -- (talk) 04:51, 18 December 2014 (UTC)
Well didn't home modems start out at 75 bps and reach 300 bps by about 1980? I can't remember the speed of the first one that I used, only that it was slow and unreliable. Dbfirs 12:24, 18 December 2014 (UTC)
In my day we had to get our internet in buckets! We'd go down to the information well, uphill both ways, rain or shine, and get one bucket full of internet to pour into our computers. Of course, to save on buckets when talking about the internet, we got rid of the "uck" and bucket got abbreviated to "bit", which is where the modern term comes from. MChesterMC (talk) 09:22, 19 December 2014 (UTC)
I started doing 110 bps in 1974. Two years later, 300. Messages became less terse. Two years later, 1200. Vroom! Email really worked well at such supersonic speeds. Jim.henderson (talk) 12:36, 18 December 2014 (UTC)

December 18[edit]

Spred Spectrum[edit]

hi.just bought a nu pc yesterday.while exploring the pc bios i come to a setup named spred spectrum.i wonder what is it for and when i click on it, it pop out +/-0.2%,0.35 & so on.i want to know what is it for.

It allows a CPU or chipset to intentionally modify the clock frequency to avoid a certain type of electromagnetic (radio) interference. Here's a very old Pentium II-era application note available from Intel for the general public: Design for EMI (1999). It explains the concept. Newer computers support this feature in many more places with many more variations. Nimur (talk) 03:05, 18 December 2014 (UTC)

ok.thank 4 the info — Preceding unsigned comment added by (talk) 05:04, 18 December 2014 (UTC)

Is ms dos supported on beagleboard?[edit]

Has anyone ever tried to install ms dos on the beagleboard?Whereismylunch (talk) 04:42, 18 December 2014 (UTC)

Has anyone ever tried to install an x86-based operating system on an ARM-based single-board computer? Quite possibly. People try all sorts of things. It seems rather unlikely to have worked though. AndyTheGrump (talk) 04:55, 18 December 2014 (UTC)
It's more likely that FreeDOS, rather than Microsoft DOS, has been ported... but if you ever played around on DOS, you know that the system doesn't abstract very much of the machine. "Making DOS run" is quite different from "making a Beagle-* computer run applications that were designed for Intel 386 on DOS". Perhaps what you really seek is Linux on Beagle-* with a supplemental, application-layer DOS-like virtual machine like DOSBOX. Nimur (talk) 15:21, 18 December 2014 (UTC)

If I wanted to use version control for text files[edit]

What could I use in Linux to get different version of text files, pictures (that are being worked on) and the like? It has to be offline.

LyX and LaTeX has SVN (Apache Subversion). Would that suit you? Better than MS Word too.--Aspro (talk) 23:45, 18 December 2014 (UTC)
You include 'pictures'. For what purpose are you wanting this revision control feature for? If it is for some heavy duty stuff, then there is a beta version of Scrivener (software) available for Linux.--Aspro (talk) 00:34, 19 December 2014 (UTC)
I use Git (software) because it allows me to commit changes even if offline and later merge with my main repository. It's fine for text. For images, a new version is, well, new. Editing binary files fills up the repository, but realistically, disks have become so large that few things you do manually can cause a problem with space... --Stephan Schulz (talk) 00:55, 19 December 2014 (UTC)
Another vote for Git here. It really has everything I want/need from version control.--Link (tcm) 10:24, 19 December 2014 (UTC)
Git is great if you are saving to a network store and will be offline a lot. If this is sitting on one computer and the files are not going anywhere, it is overkill. SVN will suffice. Best of all, you can pick sides in the eternal Git/SVN flame war and then, when you feel battle-hardened, you can jump into the Vi/Emacs flame war (and troll with Nano). Finally, when you feel really ready to waste your life, get in on the KDE/Gnome fight.
Nano and pico are both still terminal programs, so I prefer to troll with MSWord :) Also please sign your posts in the future. SemanticMantis (talk) 20:26, 19 December 2014 (UTC)
I've used CVS (back in the days) and Subversion, and there is nothing really wrong with them for most users. But I find git just as easy or even easier to set up, I can model the same workflows, and I get the distributed aspect for free if I ever need it. So I wouldn't start a new project with anything else at the moment. And, of course, the only valid choices are Emacs, vi and ed. In fact, is the standard text editor. --Stephan Schulz (talk) 21:12, 19 December 2014 (UTC)
I use GNU Bazaar because it can be used purely with a local repository or in a distributed fashion with a central server. This gives me flexibility to work offline on private projects on my own machine but later to make them accessible to a team. However, Bazaar may not be still actively developed. See also Comparison of revision control software.-gadfium 21:45, 19 December 2014 (UTC)

December 19[edit]

thermal compound/paste[edit]

Thermal grease (edit | talk | history | protect | delete | links | watch | logs | views)

thermal compound/paste is there any other alternative to replace it.can it be made by youself.if can,how?:Q — Preceding unsigned comment added by (talkcontribs) 01:50, 19 December 2014‎

There are a couple of possibilities discussed here - a toothpaste/Vaseline mix, and a diaper rash cream. [1] Neither appears to be anything but a short-term makeshift substitute, and I'd certainly not recommend either unless you are prepared to risk destroying the CPU or whatever if they fail. Thermal grease is expensive, but not as expensive as using something cheaper that doesn't do the job properly. AndyTheGrump (talk) 02:17, 19 December 2014 (UTC)

Andriod/iOS devices[edit]

Why are mid to high end tablets so much cheaper than phones with similar specs and capabilities. From what I understand, the only major hardware missing from tablets still is the cellphone radio (for WiFi only models), since most high end tablets include the motion, light, and GPS sensors. They also usually have bigger batteries. It just doesn't make sense.

Well if the specs are entirely the same, then you have far more room to work with in a tablet. Of course a bigger battery, larger screen and case would generally cost more than a smaller one, although for the screen, resolution and other factors will come in to play. Nil Einne (talk) 15:40, 19 December 2014 (UTC)
I've failed to find actual dimensions, but looking at disassembly videos of the various iPhone and iPad devices (neglecting the iPad Air) they're build to much the same format - they have a main logic board that's about 40mm wide that runs on the side (the long axis) of the device. The battery sits beside that, and the display sandwich is above both. So it looks like the phone PCB is about half the area of the tablet ones - with, as you say, about the same hardware on it. Making very small footprint, dense boards like this is expensive - generally you need more layers, more blind and buried vias, and in general more tortuous feats of routing. Again I can't find a reliable source, but it looks like iPhones have something like a 10 layer board and iPads a six layer board, with the iPhone using thinner traces and smaller vias. So the logic boards are pricier to fabricate - but by how much, only Apple and their partners know, and I don't think it's enough to explain all the differential. -- Finlay McWalterTalk 16:20, 19 December 2014 (UTC)
This story in EE Times talks about the 10-layer package-on-package board in the iPhone 4. It confirms what I've said about small traces and laser-drilled microvias. They put the price of that board at $5 (from maybe $2 for a simpler board) - so that doesn't remotely cover the differential you're asking about. There will be additional costs to stuffing such a complicated board (particularly the package on package components) - but I've no idea how much. The very dense nature at which ICs are packed will have two additional problems - thermal and EM. All these chips right next to one another, or actually stacked, means that the phone form factor will have a harder job dissipating heat into heat spreaders or the casing. The EM problem is due to the proximity of various RF systems (GSM/GPRS/HSPDA, Bluetooth, NFC, WiFi) - if they're in extreme proximity to other components, they may interfere. A tablet has a bit more space to get these (particularly their antennas) away from the digital logic and from one another. It seems the iPad Air, and some iPhone models, has an L-shaped extension to the main PCB (or a RF daughterboard connected to the main logic PCB with a flexcircuit), which allows them to put some distance, and some of the battery, between the antennas and the main logic. -- Finlay McWalterTalk 18:42, 19 December 2014 (UTC)
Without getting into the technical details of electronics (as the others have presented well), consider a few related questions - why was a laptop in 2000 significantly more expensive than a comparable desktop PC? Or in the 1960s, why was a portable radio much more expensive than a desk model? Making item A to have similar performance to item B but much smaller is almost always more expensive. Engineering is much easier when space and weight are not restrictive. Even today, a mid-range mechanical watch is more expensive than a mid-range mechanical wall clock, and the same goes for quartz clocks too. SemanticMantis (talk) 18:10, 19 December 2014 (UTC)
As to materials - some educated estimates of the bill of materials for the iPhone5 put that at $199-$230 and for the iPad Air 2 at $275 - $358. -- Finlay McWalterTalk 20:14, 19 December 2014 (UTC)
And in case people are wondering, the iPhone 6 or even 6 Plus isn't that diferent [2] [3]. Nil Einne (talk) 01:33, 20 December 2014 (UTC)

December 20[edit]

yellow spots on pages[edit]

I have a color laser jet 3600 dn printer. It does not end calibration. If I skip calibrating, and print pages, the extra yellow spots appears on pages on different locations, even if I m printing black and white page. The magnetic roller of yellow tonner contains some visible yellow ink powder on it. I have cleaned magnetic roller of yellow tonner but again it turned to previous condition. Is there any method to bypass yellow tonner or by removing yellow tonner , can I print black and white pages. mono printing option does not exist in this printer. (talk) 00:49, 20 December 2014 (UTC)

What's the matter. Don't you like the United States of America being able to track all your documents back to you? See here for an explanation of the yellow dots: Electronic Frontier Foundation - Is Your Printer Spying On You?--Aspro (talk) 01:05, 20 December 2014 (UTC)
From his description of yellow toner stuck on the roller, it sounds like a printer defect, not spying. So, the only surefire way to eliminate yellow dots is to eliminate the yellow toner and clean the roller again. Black and white pics should look good then. StuRat (talk) 02:22, 20 December 2014 (UTC)