Wikipedia:Reference desk/Archives/Computing/2012 March 7

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March 7[edit]

Factory settings[edit]

I purchased a new laptop and want to donate my old one to a charity. How do I set it back to the original settings (I no longer have any disks (of course)). (talk) 01:32, 7 March 2012 (UTC)

Do you mean the computer or the monitor (screen) ? For the monitor, there's probably a choice on the menu you get to by pushing buttons on the monitor. As for the computer, those defaults come from the operating system, so formatting (blanking out) the hard disk(s) and reinstalling that is the way to go, which will also remove any personal data. However, if you don't have the disks, you would need the validation codes to download it. If not, you're pretty much stuck with formatting the disk(s) and donating it with no O/S or leaving it as-is, which might expose your private data. StuRat (talk) 01:44, 7 March 2012 (UTC)
A lot of recent laptops have a recovery partition on the hard drive instead of separate recovery disks. There may be a factory reset option that you can select at boot time (before the operating system starts to load). -- BenRG (talk) 02:21, 7 March 2012 (UTC)

Thanks. I have already removed all personal data. (talk) 04:21, 7 March 2012 (UTC)

I don't think it's as easy as you think, since personal data is stored all over the place. StuRat (talk) 04:43, 7 March 2012 (UTC)
Assuming that you really don't want random strangers reading your personal data, and you really have deleted all content you don't want them to see, you will need to scrub the areas of the disk which once held them to prevent someone from running an undelete program or forensic program to view unused sectors of the disk. There may be a solution which allows you to securely wipe all unused areas of the disk, which I am not aware of. If such a program doesn't exist or is too expensive for you, you could backup all existing data using a bare-metal restore program, securely wipe the disk, and then restore the data again so the next user has at least an operating system.-gadfium 05:07, 7 March 2012 (UTC)
Read this, this, this and this. Removing *all* personal information is not an easy process (depending on just how sure you want to be that it actually has been deleted) but these sites run you through it. As for restoring default factory settings, unless you have a recovery disk from the manufacturer, the easiest way is just to reinstall Windows. - Cucumber Mike (talk) 08:11, 7 March 2012 (UTC)

Downloading jar file from webpage[edit]

Is there any way to download this jar file?? The browser doesn't display the source, which is very interesting... -- (talk) 04:54, 7 March 2012 (UTC)

If you use one of the common web browsers, you can display the source using a menu alternative or a keyboard shortcut. Websites can not circumvent this as far as I know. I tried to view the source for that page you linked, and it worked fine. I will not track the jar file for you, but looking at the source for the page in the iframe, I found part of the filename for the jar file, so that's a start. (talk) 23:36, 8 March 2012 (UTC)
Yes the pages "summons" (Don't know a better word) the frame, on the frame you can locate to the jar file, though the browser doesn't naturally download it.. It just like redirects you.. — Preceding unsigned comment added by (talk) 20:35, 9 March 2012 (UTC)

Allow program to make changes, no queastions asked[edit]

In Windows 7, I often get the message "do you want to allow this program to make changes to your computer?" Generally this is good, but is there a way to turn it off for specific programs? Bubba73 You talkin' to me? 06:34, 7 March 2012 (UTC)

Yes. You want to allow the program to 'Run as Administrator'. - Cucumber Mike (talk) 08:14, 7 March 2012 (UTC)
That doesn't sound right. Running as Admin would allow you to run programs which you don't have rights to run as a normal user, but that's not the question here, which is about programs the normal user does have the rights to run, but which ask for confirmations before taking certain actions. StuRat (talk) 08:43, 7 March 2012 (UTC)
This is a feature of Windows' User Account Control. Quoting from here: The primary difference between a standard user and an administrator is the level of access that the user has over core, protected areas of the computer. Administrators can change the system state, turn off the firewall, configure security policies, install a service or a driver that affects every user on the computer, and install software for the entire computer. Standard users cannot perform these tasks, and they can only install per-user software.
Unlike earlier versions of Windows, when an administrator logs on to a computer running Windows 7 or Windows Vista, the user’s full administrator access token is split into two access tokens: a full administrator access token and a standard user access token. During the logon process, authorization and access control components that identify an administrator are removed, resulting in a standard user access token. The standard user access token is then used to start the desktop, the Explorer.exe process. Because all applications inherit their access control data from the initial launch of the desktop, they all run as a standard user.
After an administrator logs on, the full administrator access token is not invoked until the user attempts to perform an administrative task. When a standard user logs on, only a standard user access token is created. This standard user access token is then used to start the desktop.
Normally, even when logged on as an administrator, you open programs using your standard user token. If the program requires your administrator token at some point (say, to edit the Registry), it will ask for it as described by Bubba. However, if you open the program as an administrator in the first place, it already has the token, hence no need to ask for it again. QED. :-) - Cucumber Mike (talk) 09:07, 7 March 2012 (UTC)
I have a program that I start many times per day on my Windows 7 computer. I run it from a desktop icon. One type of problem I've been having with it someone suggested running it in Win XP SP3 compatibility mode. Since I made that change, it is asking me that question about allowing it to make changes to the computer each time. How can I keep it from doing that (once should be enough)? Bubba73 You talkin' to me? 15:56, 7 March 2012 (UTC)

mini screens[edit]

So, if I do get one of these raspberry pi things, can anyone reccomend a decent but reasonably cheap screen I can run it on, I'm hoping for something around 6-9" that I can easily carry around with me and plug in when I need it, nothing too fancy or expensive. Also, a tiny keyboard if possible. I know someone with one that rolls up to fit in his pocket but it often doesn't work too well. (talk) 18:36, 7 March 2012 (UTC)

Why? It's basically a Microcontroller for installing your own toy robot or whatever. Keyboard or screen would not help it do this. Jim.henderson (talk) 19:03, 7 March 2012 (UTC)
The Raspberry Pi is quite capable of working with a keyboard and screen, and will probably make a reasonable tool for web browsing - and indeed Wikipedia editing. It may not have the capabilities of a modern desktop PC, but the ARM CPU is a similar model to that used in iPads and the like.
In answer to the original question, I've been looking around for the same thing, but without much luck so far - at least, on a budget. AndyTheGrump (talk) 19:17, 7 March 2012 (UTC)
Ah. I didn't realize. So, when you add the keyboard, screen, Wi-Fi radio, browser and interface software, you'll end up with a tablet similar to the low-end seven-inch Coby Electronics Corporation Kyros I bought new last month for $90 USD, but larger, slower, more fragile, more expensive and less versatile. Very good. Jim.henderson (talk) 03:48, 8 March 2012 (UTC)
Keep taking the tablets. ;-) AndyTheGrump (talk) 06:28, 8 March 2012 (UTC)
One typically low-cost option is to get a rear-view monitor intended for use in a car. These can be very cheap, and typically have an RCA connector to hook up to the Raspberry Pi. The resolution might be marginal, though. The other output is HDMI, but I think it's pretty unlikely to get a small, low-cost monitor supporting that as an input. Buddy431 (talk) 06:21, 8 March 2012 (UTC)
Why get a monitor at all? Get a HDMI cable and plug it into any handy TV screen (that supports HDMI obviously). After all, the objective of the raspberry Pi is " stimulate the teaching of basic computer science in schools" in the same way as the BBC Micro/Commodore 64/ZX Spectrum did back in the 1980s and back then we didn't rush out (at least not straight away :-) to buy a new TV just for the computer. Astronaut (talk) 14:52, 8 March 2012 (UTC)
Yes - that's the whole point of the R Pi. For around thirty quid (inc. VAT and delivery), I get a nice little toy I can plug into stuff I've already got. I'll probably end up spending another £20 or so on bits and bobs (power supply, USB hub, SD card etc), but I'll have something I can play around with to my hearts content. I've already got a ridiculously-overpowered desktop gaming PC, and a cheapo netbook, so I don't need another computer. This is a toy. It may also be useful, though in what ways I don't know yet. AndyTheGrump (talk) 16:41, 8 March 2012 (UTC)

I just wanted something that I could use whilst out somewhere or sitting on my bed, rather than needing the huge heavy screen from my main computer. (talk) 23:47, 8 March 2012 (UTC)

How does a call to a cell phone find its destination?[edit]

Routing in the PSTN doesn't say. Does the carrier keep a table of the current locations of all phones? I assume the call is first routed to the central office owning the phone's number, and from there it's forwarded to the appropriate tower, but how the "appropriate tower" is known and the mechanism of forwarding aren't clear to me. Is it different for international calls? -- ke4roh (talk) 19:17, 7 March 2012 (UTC)

When a GSM phone moves into a new cell, it "registers" with that cell (strictly, I think a given phone can be registered to several adjacent cells, to handle cases where it's moving and where the strength of signals from the different towers varies with terrain). That tower signals home to its owner, which in turn looks up the phone's home carrier and it signals to that company. So if you're abroad, your come carrier knows which country you're in (and which network you're temporarily registered with there). And that network knows which cell(s) you're in. (talk) 19:41, 7 March 2012 (UTC)
Most mobile telephones have a globally unique identifier - either a Subscriber Identity Module, a Mobile Equipment Identifier, or an International Mobile Equipment Identity (in practice, often a combination of two or more such ID numbers). This is very different to the internet; while most ethernet cards do have a globally unique MAC address, the MAC address is explicitly not used by the internet protocol. In fact, the internet protocol trusts its routing tables, while a mobile telephony network protocol explicitly does not. This is one reason why you can't get free subscriptions to a telephone network by "faking" your phone number! The network relies on secure certification to prove that your phone is authorized and routable.
As a result of the uniqueness of a mobile telephone's identity, routing to its address can be managed with a much faster, more scalable protocol. This is what enables the "cell" part of "cellular" - a mobile device can switch towers - it can even switch network providers - all without losing network connectivity. For example, the GSM network is designed to use a global, authoritative giant centralized database. Contrast this with internet protocol, which does not rely on any centralized routing.
At least a few resources online refer to SS7 packets, which actually convey the data that, for example, updates the Home Location Registration database. This would be similar to the ARP portion of the OSI stack; but beyond this level of detail, my familiarity with GSM is exhausted. There are some resources at our external links section that look very promising. Nimur (talk) 22:28, 7 March 2012 (UTC)
Strictly, the Home Location Register (HLR) isn't global - there is one per mobile operator. When a user moves out of their own network operator's "reach" and roams onto another network, the new network notes their location in their Visitor Location Register (VLR) and informs the owning network, who enter the VLR details in their own HLR. So a call to them when roaming first goes to their own network provider, who then refer to the roamed network provider, who determine the relevant tower from their VLR. --Phil Holmes (talk) 17:16, 8 March 2012 (UTC)

Digital Photo Frame[edit]

How does it actually work ? Is it LCD or E-ink (article is not much helpful) (talk) 23:25, 7 March 2012 (UTC)

I've seen an LCD version. However, that doesn't exclude there being others using different technology. StuRat (talk) 03:28, 8 March 2012 (UTC)
E-ink is primarily a monochrome technology - they have a product with 4096 colors, but that is a fraction of the what most LCD screens offer. --LarryMac | Talk 13:03, 8 March 2012 (UTC)
(EC) As hinted at in Electronic paper and a simple search will confirm, commercial colour e paper displays are still very rare, even with e-readers. In the case of e readers they only really became available over the last year using Qualcomm Mirasol screens which are Interferometric modulator display, and E Ink Triton screens which are electrophoretic [1]. (The Mirasol is only entering in to mass production later this year [2].) They are also very expensive. So while it's possible someone produced a colour eink digital photo frame, it's unlikely and it will be very rare. Also the colour depth of such displays seems to be still fairly low, e.g. E Ink Triton only does 4096 colours. I'm not sure of Mirasol, but it doesn't see much higer. So photo quality likely won't be that great anyway.
Pixel Qi is planning to introduce displays which can keep colour even when the backlight is off [3] [4] (their previous screens lost colour when the backlight was off) although I'm not sure what sort of colour quality it will achieve in that mode. I'm also not sure whether the reflective mode in Pixel QI displays is really as good as e paper displays. And in terms of power consumption, I believe even without the backlight (in reflective mode) power usage for the display is still fairly high compared to e paper displays. The E Ink Triton is I believe zero power for static display. Despite some confusing contradictory information including in our article, I believe the Mirasol at least isn't quite zero power, see the comments [5] and [6]. However the power usage is apparently around 1 mW [7] [8] [9]. This [10] gives 0.1W for a Pixel QI type display without backlight. (Due to the way LCD works, I don't believe the power usage will vary that significantly if the image is static.)
In any case, it's a moot point as the Pixel QI product able to retain colour without the backlight still isn't available [11] so even if someone wanted to make a digital photo frame with one, you won't be finding it yet. (Also 10" would be a fairly large photo frame.)
Nil Einne (talk) 15:08, 8 March 2012 (UTC)