What is the best distro or way to have a Raspberry into a Kiosk Mode?

Question: I need to setup a Raspberry Pi to start and open a browser with a specific URL in fullscreen mode. I have been using Ubuntu Mate and Firefox to do that, but I would like to know if there is a better way to achieve this goal?
Comment: You may want to check out [fullpageos](https://github.com/guysoft/FullPageOS)
Answer: I learned about nodm today from this answer, to a question that is only a slight variation on this one. "Nodm" sounds clever and likely works on almost any distro; I notice the Arch linux wiki has a page about it with some additional useful information -- most significantly the point about disabling (other) display managers (this is not a recommendation to use Arch, but because they have better documentation than most other distros, and most of that information is about software that is used on other distros as well, such as systemd, which is mentioned in that article with regard to disabling the normal display manager).
Display managers (DMs) are the programs that present a graphical login.  They are a distinct entity from desktop environments (DEs), since different users of the same machine may choose to use different DEs (and in fact, you can have simulataneous logins of different users running different DEs; the sessions run on separate virtual consoles and can be switched between using CtrlAltF-[1-6+]), but the login is always the same DM.  Last I checked, the display manager used on Raspbian was lightdm, but there are others -- it doesn't really matter which one is in play as long as you know what it is because again, all you want to do is disable it.
I mention all that for a couple of reasons:

On a distro with a default GUI, the DM is going to get in your way, because you want a GUI, but you don't want a DM, but the way things are configured on such a system, the DM is run as an init service.  You need to circumvent or supplant this service via the init system (which is usually systemd).
To do that so you can still work with the GUI effectively you need to understand how the the GUI stack works.  Like any software stack, it is composed of layers:

The first, most fundamental layer, common to the vast majority of GNU/Linux systems, is the Xorg server.  You need this.
The second layer normally is a window manager (WM).  You may want this.  Note the more elaborate diagram of the GUI stack in that wikipedia article.
The third layer, normally, is a DE.  On Raspbian this is by default PIXEL, a recent fork of LXDE.  You almost certainly don't want this.

Personally, I would start with a distro with no GUI (such as Raspbian lite), and add components to get what I want, rather than starting with a desktop system and modifying it to create a kiosk.  However, that is just an opinion, and I can't say it will be easier unless you understand what you are doing, which is why I am painting a big picture here and including a lot of links to other reading.
Working this way, the goal can be broken into two:

Create an init service that is going to do what a DM usually does, namely, start the Xorg server at boot and run an application on top of it, possibly with the aid of a WM. Something to be aware of here is that you probably do not want the X session to be a root session, hence autologins are sometimes used for kiosks.  Another option is to simply downgrade privileges, since the root user can start something as someone else.  However, there is a serious weakness in that if someone is able to stop whatever and return to a root login, so you would want to do that with no login, which is how init services work.
As tjohnson notes in a comment below, nodm is probably a perfect way to deal with these issues.
Get your application to run inside X the way you want it.  This is really the easy part, since it is mostly just a matter of telling X what command(s) to run.  Normally that's a DM or DE, but it can be a standalone application such as a web browser.
Comment: Thanks for linking to my answer about `nodm`. I just updated it with more details about how to use `nodm` with Raspbian Lite to create a kiosk environment starting from scratch. If I understand correctly, `nodm` works the way that is desired regarding user login, because in the config file you can set `NODM_USER` to "pi" (or any username), and it works differently from other DMs like LightDM in that it doesn't require the boot behavior to be changed to automatic GUI login. If you're using `nodm` and press `Ctrl+Alt+F1` to switch to the terminal, you have to enter your password there.
Answer: I use Arch Linux + Openbox + Crontab + Surf + OMXPlayer.
In my case (video-advertising installed inside gyms, shops, ..) I have customers ads spots running over an HTML page used as background with news, weather info and date-time.
Automated Power On Steps:
- wifi connection
- login
- start Openbox
- start surf (browser) in fullscreen mode
- run omxplayer daemon with video playlist (https://github.com/subogero/omxd)
Automated Checks and Commands:
- TV power on/off (CEC technology, LG tvs don't accept "poweroff" command)
- restart services (surf, omxplayer, ..) if they crashed
- reboot during night
- ..
If you intersted and you need more details, I can update this answer with step-by-step commands and configurations required.
EDIT:
!!!
1. Following tutorial is not complete, you have to use it as guideline. I suggest you to read it all once, to read something on linked sources and manipulate it as you need.
2. My project is based on the RaspberryPi 3 computer with ARM architecture. Some instructions are direclty related to it, they have a triple comment symbol (###).
3. TV management via CEC technology is available only for the RaspberryPi and a few other devices. You can buy an adapter for all others computers. Have a look to the vendor compatibility to know which TV to use/buy.
!!!
1 - Arch Linux Installation ARM. You can use a 32/64bit version as well: archlinux-arm-rpi3  ###
2 - Installing packages (from root):
# xorg, xorg-xinit: for desktop-environment and drivers
# netctl, net-tools, dialog, wpa_supplicant: for wifi connections
# wpa_actiond: for auto managed wifi connections
# openbox: desktop-environment
# surf: light browser web
# cronie: tasks scheduler
# libcec: tv manager over CEC technology
pacman -S xorg xorg-xinit netctl net-tools dialog wpa_supplicant wpa_actiond openbox surf cronie libcec

3 - [Optional] Create new user and delete the default one (from root): source
useradd -m -g users -G storage,video,audio,power -s /bin/bash USERNAME
userdel -r alarm ###

4 - Autologin (from root): source
# move into login services folder
cd /etc/systemd/system/getty.target.wants/
# create a copy of current login service and edit it
cp firstname.lastname@example.com email@example.com
# edit one line in email@example.com
# from: ExecStart=-/sbin/agetty --noclear %I $TERM
# to:   ExecStart=-/sbin/agetty -a USERNAME %I 38400
# -a parameter passed is the abbreviation of --autologin
# disable current login service and enable the new one
systemctl disable email@example.com
systemctl enable firstname.lastname@example.com
reboot

5 - Auto startx (from user): source
# if .bash_profile doesn't exist into user's home
cp /etc/skel/.bash_profile ~/.bash_profile
# append following lines to .bash_profile to autorun startx at login
#if [[ -z $DISPLAY ]] && [ -n "$XDG_VTNR" ] && [ "$XDG_VTNR" -eq 1 ]; then
#    exec startx
#fi
# copy new .xinitrc file into the user's home and edit it, to run openbox with startx command
cp /etc/X11/xinit/xinitrc ~/.xinitrc
# comment last lines (from 'twm &') and add following line
exec openbox-session

6 - Enable the task scheduler and auto managed wifi connection
6.1 - enable task scheduler service to run on boot: source
systemctl enable cronie

6.2 - enable and set auto managed wifi connection: source
# get wifi adapter name
iwconfig
# enable the wifi manager
systemctl enable netctl-auto@WIFIADAPTERNAME
reboot

7 - Run software you want after autologin (from user): source
# example: run a webpage in fullscreen
# 1. copy openbox configuration files into user's home
#    cp -R /etc/xdg/openbox ~/.config/
# 2. edit autostart to run the browser, add following lines
#    surf -F ~/index.html # or surf -F http://google.it

8 - Set periodic checks (from user):
8.1 - TV on/off check: ### source
# create a .sh script to get TV power status and decide if to power on/off
# you have to filter the result with cut or awk, I can't give you now the correct script
> #!/bin/bash
> # get TV status
> # usage: ./tvstatus.sh
> # status: on
> #         standby
> #         unknown
> echo 'pow 0' | cec-client -s -d 1

8.2 - software/services checker
# create a .sh script to check if a process is running
> #!/bin/bash
> # retrieve if given process is running or not
> # usage:   ./isrunning.sh PROCESSNAME
> # example: ./isrunning.sh surf
> if [ "`ps -C $1 | grep $1`" != "" ]; then echo 1; else echo 0; fi
# create a .sh script to run once a command checking if related process is not running
> #!/bin/bash
> # run once a command if related process is not running
> # usage: ./runonce.sh PROCESSNAME COMMAND
> # usage: ./runonce.sh surf "surf -F ~/index.html"
> if [ `./isrunning.sh $1` = 0 ]; then bash -c "$2"; fi
# 6.3 - set the task scheduler with checks to run
# create a temp crontab config file (or edit it directly with 'crontab -e')
> * * * * * /home/USERNAME/main.sh
# assign new configuration
crontab CRONTABCONFIGFILE
rm CRONTABCONFIGFILE
# inside main.sh you can write all checks/commands you need (in this case, they are runned each minute. Have a look to the source if you are not familiar with crontab)

There a lot of stuff/checks to run, you can scheduling the TV power on/off using libcec and a json file (read it with JQ) or get temperature from rpi using vcgencmd. I can't give you all information because mine is a commercial project. If you need more help, I'm here, sorry for the late answer. I suggest you to have a look to all sources (if you don't already know) to understand better all steps and to know how to expand them with new features.


What are the pros and cons of mixing horizontal scrolling with vertical scrolling?

Question: I'm working on a new site for a company. We are working on a new concept for them, using horizontal and vertical scrolling. We know that the users that interact with the sites are advanced users so a little of complexity in the navigation is not an issue. I wonder what are the cons (and pros) of having horizontal scrolling. What are your thoughts of mixing vertical scrolling (to go between different sections of the sites) and horizontal scrolling (to navigate through the content of one section of the site).
Comment: when you mean vertical scrolling, you mean scrolling down a complete page or are you talking within an iframe ?
Answer: Jakob Nielsen argues against horizontal scrolling (still actual):.

We know from user testing that users hate horizontal scrolling and always comment negatively when they encounter it. Customer satisfaction is surely reason enough to avoid horizontal scrolling. There are two other reasons as well:

On the Web, users expect vertical scrolling. As with all standard design elements, it's better to meet user expectations than to deviate.
When pages feature both vertical and horizontal scrolling, users have to move their viewport in two dimensions, which makes it hard to cover the entire space. For people with poor spatial visualization skills, it's especially challenging to plan movements along two axes across an invisible plane. (Typically, users score lower than designers on spatial reasoning and visualization tests.) In contrast, one-dimensional scrolling is a simple way to move across content without advance planning: you just keep moving down.

Personally I think it's a bad idea to use horizontal scrolling for non-touch devices. You may use some kind of switchers (like next/previous category buttons) and animation to emulate horizontal scrolling, but modern input devices (with few exceptions, like Apple's Magic Pad, etc) still doesn't provide a good experience with horizontal scrolling unfortunately.
Comment: I've added in some detail from the Nielsen article you reference. If you're going to link elsewhere to provide some additional information then it's recommended that you provide some information from that link so that your answer isn't just a link of elsewhere, but is actually an answer. (Plus there is always the risk of link-rot too).
Answer: I think you've already identified the advantage of mixing vertical and horizontal scrolling: the possibility for more natural navigation across two axes. We are seeing this more in touch-based interfaces, where an interface consists of a vertically scrolling list of horizontally scrolling lists. Vertical scrolling through the main list navigates through categories, where horizontal scrolling through each individual list navigates content within the category. This interaction style works on a touch-based device because the actions required for vertical and horizontal scrolling are nearly equivalent, simply tap and drag.
The disadvantage is that this does not translate to a more traditional web experience. On the web, the user is likely interacting with the site using a cursor controlled by a mouse, touchpad, or other mouse-like device. This exhibits the following characteristics:

The web does not natively support "click and drag" type scrolling, nor does a cursor afford this type of interaction. You can implement it for your site, but it's unexpected behaviour. This also disables selection and highlighting, which may frustrate users.
The devices controlling the cursor often have vertical scrolling mechanisms built into them, scrollwheels on mouses and multitouch or special areas of touchpads are examples. This makes vertical scrolling considerably easier with these devices. However, similar mechanisms for horizontal scrolling are considerably rarer. This makes horizontal scrolling inherently more difficult than vertical scrolling, forcing the user to resort to using the scrollbars.
Comment: I like your points about the hardware and their vertical scrolling mechanism. Could be an (or the one most annoying) issue using Win8, because there, horizontal scrolling is default behaviour in the Metro gui.
Comment: I've actually implemented web browser click and drag  scrolling that does *not* disable selection and highlighting. See [Utterscroll](http://www.debiki.com/dev/utterscroll). I agree that using the scrollbars for horizontal scrolling is not good.
Answer: Scrolling on two axes massively harms "full search discovery":
Use case: I dimly remember there was a treasure map on this page, but where?
Scrolling all through one axis is fairly simple, and I can skim over everything quickly.
Having a window to a larger surface I have to plot out an algorithm and have to focus my attention on executing this, slowing me down considerably. (It might be relevant that every such algorithm requires mental state.)
"Scrolling down down down" is pure muscle memory. "Scroll right until you can go no further, then scroll down exactly one page, scroll left until you can go no further, then scroll down exactly one page, repeat" is not.
I'd also wager a guess that in general, making a mental map in one dimension might be easier - you need to remember roughly "before or after", instead of, say, "a little to the left and far to the top".
That argument is reversed though if there is a natural topology (say, exploring a map of Europe). This is actually the main use case for 2D navigation.

Horizontal vs. Vertical: I recently realized that scrolling horizontally on a touch interface might me a more natural movement (unverified epiphany), whereas scrolling vertically matches mouse input better.
Scrolling vertically works better for text reflow: fitting text to the available width and extending to the bottom.
OTOH if you have elements with a fixed size, on a landscape display less items are cut off by the rim if you scroll horizontally.
Answer: If the users of the site will spend a considerable time reading content (enough to span multiple columns, over multiple pages), then you may be interested in this paper presented at the WWW2009 conference:
Scrolling Behaviour with Single- and Multi-column Layout
The abstract (with added emphasis as it may pertain to your question):

The standard layout model used by web browsers is to lay text out in a vertical scroll using a single column. The horizontal-scroll layout model--in which text is laid out in columns whose height is set to that of the browser window and the viewer scrolls horizontally - seems well-suited to multi-column layout on electronic devices. We describe a study that examines how people read and, in particular, the strategies they use for scrolling with these two models when reading large textual documents on a standard computer monitor. We compare usability of the models and evaluate both user preferences and the effect of the model on performance. Also interesting is the description of the browser and its user interface which we used for the study.

I know that this paper is dedicated to a very specialised case, mainly focused on text, but I hope you find it useful. There may be other studies that are more focused on the intersection of scrolling-behaviour and navigation design that I am not aware of at this time.
One example (if you'll excuse the reference to an iPad app) that utilizes both vertical and horizontal scrolling is the New Yorker magazine app. At the time of writing, the reader swipes/scrolls horizontally to move between articles/sections, and swipes/scrolls vertically to read more about the current article/content. It felt 'odd' at first, but you quickly become accustomed to it. Again, this is an example of a text-heavy application (magazine).


Is it "pestering" to email a professor for a recommendation after no response the first time?

Question: I talked to a professor about writing a recommendation (sometime before winter break) and he verbally agreed to it, and I sent him the official email request during winter break. He has not responded (I suspect it is because I sent the email during winter break) and out of politeness I didn't put his email down for reference requests without his consent. Is it considered pestering if I send him a follow up email now, restating my request? It has been about 3 weeks, and deadlines are in February and I wish to give at least a month's time to write the rec.
Answer: It's not pestering. Professors are busy people and he probably just forgot. One polite reminder email will not go amiss.
Comment: @Marcus something along the lines of "Hi X, Before Christmas we discussed the possibility of you writing me a reference letter. Are you still ok to do this? If so, the first deadline is 13th February. Thanks, Marcus" should be fine (modify according to the formality of your relationship).
Comment: Should I write the email as if it's my first time asking him, or should I reference my prior email?
Comment: I can only speak for myself, but I appreciate and encourage students to "pester" me, as I can easily miss or forget about a request.
Answer: Most profs leave things like this to the last second... many even are bad and miss deadlines. No recommender I am aware of would start drafting a month in advance and carefully craft before submitting. Work level is so high that they will just crank this out when the deadline motivates them.

if deadline is hard (NSF, etc.) be sure your reminder states this
provide info to help them write (your CV, research proposal, etc.)
if there are any good stories of your work with this person not included in your CV that would be good for him/her to include, briefly summarize them.
Answer: It's not pestering. Neither it is a good sign. Professors are always busy, still they are supposed to be professionals who prioritize their work and try as hard as they can to get the to bottom of their to-do list.
Sending a new polite e-mail with a reminder is certainly a good idea as he/she might just have put you down on her/his priority list. However, you need to be prepared to accept that you may 1) be down on their priority list for reasons of not being particularly enthusiastic to write that letter or 2) be facing a too busy (sloppy?) professor who may send a letter too late.
Just send the new e-mail and gauge the reaction.
Answer: did anyone consider that winter break is supposed to be just that, a break?  Professors don't give you assignments during that time, so please consider their needs to work on research or take a break over the holidays, as they so richly deserve.  It was self-centered of you to send the request during the break.
Comment: @BobBrown At least here, there are holidays for the students which are not holidays for scientific staff, but many of the scientific staff take their days off during that time. So it is very common to have a professor put up specific office hours during the so-called "time without lectures"/ students breaks.
Comment: Two deans ago my boss said faculty web pages should indicate our availability during breaks and holidays.  I wrote, "None.  They's why they're called 'breaks' and 'holidays.'"
Comment: I don't think it was necessarily self-centered.  It *was* probably ill-advised as now that email is "below the fold" in the professor's inbox.
Comment: Yeah I made a mistake but it was also because our break is very long, and had I waited till after break I would have either missed out on a lot of program deadlines or given my profs a single week to write the recs. They did reply though so I'll make sure to thank them profusely in person.


Cartan involution for finite W-algebras

Question: Does anybody know if there is an analog of the Cartan (anti)involution for W-algebra
associated to a nilpotent element e, which is principal in some Levi subalgebra
of semi-simple Lie algebra g? Actually, I am more interested whether there exists an analog of the Shapovalov form on a Verma module for such a W-algebra.
Answer: In the affine case, there is a related discussion in a paper by Kac-Wakimoto;
see pp. 23-25 in arXiv:math-ph/0304011v2.

Cartan involution for finite W-algebras


What are Windows hidden shares good for?

Question: What is a Windows hidden share? And what is it good for?
Does removing Windows server default hidden shares impact the system?
Answer:
What is a Windows hidden share? And what is it good for?

Simply a share that isn't displayed by normal means in the network. Other users will not see your shared folder/files. Certainly it is not a means to secure shares from others, since many networking tools can still find these shares. Hidden shares have the exact same security characteristics of normal shares, though. So you can still create permissions and require passwords to access them.
Hidden shares may be useful if you want to share a file or folder to someone and don't want it listed on everyone else's computer. They are particularly useful to programs that require shares to be function (like some server software, or some specialized software like Virtual Machines), since any number of shares can be created without clogging the list of shares your computer publicly advertises on the network.

Does removing Windows server default hidden shares impact the system?

Not normally. Not unless your computer is on a network. Certain administrative functions also make use of these "default" shares (called Administrative Shares). But to my knowledge, always in the context of networking. So I would say, if you are not in a network, it's safe to disable these shares.
Note that these shares are secured with your computer administrator credentials. So they are very safe unless someone knows your administrator account. But, if they do, a lot more than your administrative shares will be compromised :)
Answer: This technet  article explains how to make your own windows hidden shares, and gives you some information about them.
From the article:

Hidden administrative shares that are created by the computer (such as ADMIN$ and C$) can be deleted, but the computer re-creates them after you stop and restart the Server service or restart your computer. Hidden shares that are created by users can be deleted, and they are not re-created after you restart your computer. Microsoft Windows XP Home Edition does not create hidden administrative shares.

Removing the drive letter shares will prevent administrators from having remote file system access. If you really need that level of security on your system, you might want to just disable the server service.
Answer: They are exactly that.  Just shares. I wouldn't worry.  Share permissions are weak.  NTFS permissions(those that are stored on your disk) supercede share permissions.
If a service decides to wander into the share permission, they'll just get denied at the disk because of NTFS.  Share and their permissions are left in for backwards compatibility.


Why is there a maximum altitude to restart a jet engine?

Question: On all the turbojets that I have flown the maximum altitude a pilot can attempt a restart is 30,000 FT MSL.  What factors go in to deciding what the maximum altitude is for an engine restart / relight?
Comment: It's the minimum pressure needed to get the combustion going.
Comment: I suppose if nothing else, unless they wanted to make it a rocket engine instead, they had to pick *some* value as the guarantee ceiling...
Answer: Basically, it gives the pilot the altitude and airspeed at which the engines can be relighted in flight. Based on these values, the pilot has to take a decision to descend etc. A jet engine requires (compressed) air, fuel and a flame source for (re)starting. So air density plays an important part in determining the maximum restart altitude.
In addition, there are other factors at play as well. In case of unassisted (without APU, for example) windmill restarting, the airspeed must be enough to overcome the inertia of the components. In certification memorandum on Turbine Engine relighting in flight, EASA says,

.. as core - bypass ratio of engines continues to increase,  higher  airspeeds  are  generally  required  to  enable  unassisted  windmill   restarting.  The  inertial  effects  because of the increased size, mass,  and number of engine driven gearbox accessories may also contribute  to   increased  rotor  drag  loads,  decrease  starting  performance,  and   possibly  contribute  to  rotor-lock  conditions.

In case a starter is available, the airspeeds required go down (as APU itself is usually a small turbine, the altitude effects are not as pronounced). According to CFR § 25.903 Engines:

(2) An altitude and airspeed envelope must be established for in-flight engine restarting, and each engine must have a restart capability within that envelope.
(3) For turbine engine powered airplanes, if the minimum windmilling speed of the engines, following the inflight shutdown of all engines, is insufficient to provide the necessary electrical power for engine ignition, a power source independent of the engine-driven electrical power generating
system must be provided to permit inflight engine ignition for restarting.

The engine restarting envelope is decided both in terms of altitude and airspeed. It also depends on aircraft. For example, in ETOPS aircraft, the APU must be designed to have airstart capability throughout the normal flight envelope. Regarding this envelope, EASA says,

2 Envelope of Altitude and Airspeed
2.1  Sufficient flight tests should be made over the range of conditions detailed in 2.2 and 2.3, to establish the envelope of altitude and airspeed for reliable engine restarts... The effect of engine deterioration in service should be taken into account.
2.2 Altitude and Configuration. From sea-level to the maximum declared  restarting altitude in all appropriate configurations likely to affect   restarting, including the emergency descent configuration.
2.3 Airspeed. From the minimum to the maximum declared airspeed at all altitudes up to the maximum declared engine restarting altitude. The airspeed range of the declared relight envelope should cover at least 30 kt.
Answer: Like most chemical processes, combustion becomes easier and faster with higher pressure. The combination of speed (which provides ram pressure) and altitude (which provides atmospheric pressure) must result in sufficient pressure in the combustion chamber. That is the reason for the stepped altitude limit. If density were the reason, there would not be a need to reduce the maximum restart altitude at lower speed.
For combustion to take place, first the fuel droplets injected into the air stream need to evaporate. This is made easier by higher temperature and pressure, and the lower both are, the more residence time of the fuel-air mixture in the combustor is required for good combustion. Next, the ignition system will add enough activation energy to start the combustion process. When the fuel-air mixture arrives at the ignitor, the fuel must have sufficiently mixed and evaporated for ignition to occur.
In case of the turbojets you have flown the pressure above 30.000 ft will not be sufficient to light the fuel, especially at the low compression ratio of the starter-driven or windmilling compressor.
Comment: @KorvinStarmast: Let's see: m dot is density times area times speed. For ignition, speed is bad: The longer the fuel has to evaporate, and the longer the fuel-air mixture stays around the ignitor, the better. You need to get the mixture ratio right, the activation energy high enough and the speed low enough, then ignition is ensured. Density is implicitly contained in pressure, because the gas laws tie them and temperature together. m dot is only important after ignition when a minimum thrust level needs to be reached.
Comment: Yeah, the memory was a bit sticky.


Is "level" control amplifying or attenuating?

Question: On the Zoom H4N, the "level" control goes from 0 to 100 (or is it 1 to 100?).  What does it do actually?  Specifically, is it controlling the degree of amplification of the incoming signal, or attenuating the incoming signal, or either around some true neutral setting?
Answer: There usually is a "native" setting called Unity. At that position, the signal is neither attenuated nor amplified artificially.
Basically you need to see what is the Unity for your particular device, and try to keep it at that level.
With 24bit recordings, softer sounds can always be successfully amplified/normalized in post.
Of course, you don't want to overload the input either - use built-in limiters if they are effective, or control the input via the external mixer/preamp.
Comment: So if there is a marked *unity* position, that's easy. I also wonder if scales that are marked in −dB implies 0 is unity thus the knob attenuates. No, that doesn't fit, on a power amp it is obviously applying gain. I figured 0 means full blast.
Comment: I thought your question was re. mic preamp, not power amplifier. In mic preamp, unity paradigm applies.
Answer: In the absence of a separate "gain" control then the level control is probably attenuating the already amplified signal (considering the mics on that device are built-in so the amp input sensitivity wouldn't need adjustment for general use)/
The 0-100 represents the inverse of the signal attenuation.
Comment: So maybe it works differently on each input. It makes sense that the mic input simply replaces the built in mics so handling would be the same and it wants something that behaves like its integral ones.
Answer: I would guess that it amplifies the signal as this is the case most of the time.
An easy way to test this in any device is to record a tone (or anything with a standard comparable level) twice, once with a level of 10 and once with level 100.
Take care to not clip the louder recording and to disable any effects, especially compressor / limiter.
Then listen to both files but turn the volume down on the louder recording until the tone is heard at the same level.
That way you will be able to listen to the difference in hiss/self noise of the preamp.
If it is exactly the same, then the preamp has a constant value and the level is an attenuator.
If the recording done on level 100 has more noise, then it is an amplifier.
In general, most portable recorders and preamps of that price range, are rather noisy, so it is better to record at the lowest possible preamp setting and raise the volume afterwards. Of course that will affect your ability to monitor the recording properly, so try to find the balance between noise and monitoring level.
I think that the idea is to pinpoint the different types of noise and choose which to avoid depending on the tools used. There is the self noise of the microphone, there is the noise caused by the preamp and there is the noise caused by the A/D conversion.
Microphones have a constant S/N ratio, so raising the preamp value will raise their noise accordingly.
Preamp's self noise is raised exponentially as you reach higher gain values.
And finally A/D conversion noise is unchanged no matter the preamp gain and microphone.
So recording with low gain VS recording with high gain:
The mic S/N is constant in those too cases since it is the ratio of the signal to the mic's self noise.
The preamp noise is higher the more gain you add to it so the High Gain recording will have more preamp noise when compared at the same playback level with the Low Gain Recording.
And finally the A/D noise floor will be further away from the signal in the high gain recording, when in the Low Gain it will be raised along with the signal in playback.
Comment: I edited the original answer and added more info on the different types of noise.
Comment: Good point: testing the S/N to see which settings are best or to be avoided is the real thing we want to know.  Why does the higher amplification produce a lower S/N instead of amplifying the noise and the signal by the same amount.
Comment: I think that the idea is to pinpoint the different types of noise and choose which to avoid depending on the tools used. There is the self noise of the microphone, there is the noise caused by the preamp and there is the noise caused by the A/D conversion.


Does Answering your question increases points on SO?

Question: So I work with WSO2 frameworks and there are not a lot of developers for it out there. I posted a question regarding it yesterday but did not get any kind of response. Now that I have figured it out on my own, will it help my reputation on SO to add it's answer as a comment?
Comment: As a comment? No, please [feel free to answer your own questions](https://meta.stackoverflow.com/q/250204/1233251), as long as they're of good quality. In terms of reputation, you just don't receive 2 points for accepting it.
Answer: Answering your own questions is something that's actually encouraged in contexts like yours. There's even a badge you can get from answering your own questions:

Besides this badge, you can get upvotes and downvotes for that answer, just like you can get them from any other answer or question. However, you won't get any perks from "accepting" your own answer (ticking the green check next to it), just like you can't upvote or downvote your own posts.
Answer: Yes, you should answer your own question, but not as a comment.
According to the Help Center, answering your own questions is encouraged:

Can I answer my own question?
Yes! Stack Exchange has always explicitly encouraged users to answer their own questions. If you have a question that you already know the answer to, and you would like to document that knowledge in public so that others (including yourself) can find it later, it's perfectly okay to ask and answer your own question on a Stack Exchange site.

From Stackoverflow blog, by Jeff Atwood on July 1, 2011:

It's also perfectly fine to ask and answer your own question, as long as you pretend you're on Jeopardy! — phrase it in the form of a question.
Answer: Writing your own answer and getting upvotes on it does give you reputation points as normal.
Marking your own answer as accepted however, does not give you any reputation gain.
A blog post by Jeff Atwood says:

No reputation is earned. Normally, accepted answers confer +15 rep to the answerer and +2 to the owner. Owner accepted answers do not earn rep (or badges) for anyone.

Although you can now earn a badge since that blog post was made, the rules on reputation are the same.


Are smurf accounts allowed in Smite

Question: I know there are complaints of many smurf accounts at low levels, but are they technically allowed? Are there any instances of people being banned for using smurf accounts?
Comment: @gruntswilldie Yes, but referring 3 friends that all have to reach lvl 15 is overkill. Not only do you have to find 3 people who would be interested in Smite, but then babysit them and make them play 20-30 hours. Making smurfs is way easier.
Comment: Unless stated in their Terms of Service, End User License Agreement or any other terms or license you agree to for Smite, which I never saw or heard of in any games so far, they are allowed.
Comment: Sadly, with things like the Tyr Sock Puppet Skin, smurfing is almost encouraged, as to unlock it you need to refer 3 other people who all made it to Smite lvl 15
Comment: @TheFaster it's called refer-a-friend for a reason ;)
Comment: Smurf accounts are everywhere, the problem is when people do bad stuff with them. For example, there is people throwing games in competitive Overwatch (common stuff in South America).
Answer: Smurfing is not illegal, it is not against the Terms of Service of Smite.
However, it is frowned upon by the community, not only in Smite but in many other games because of the huge advantage an experienced player has over newbies.
Smurfing won't get you banned as long as you don't violate the terms of service while playing.
If you don't want to discourage new players but also really want to smurf, play supporting champs/gods/heroes/... and try to hold back. Give tips, don't steamroll over them.
Answer: I'm somewhat new to Smite, having a level 7 account now. I had went 25-8 in a Joust game, where my teammates weren't very good with their gods and I was basically carrying. We ended up losing that game, however when we got back to the match lobby, the other team started whining at me, calling me very hurtful names and accusing me of Smurfing. They reported me and basically ruined my day.
What I'm trying to say is don't just assume that someone is Smurfing just because they're doing very well in the lower levels. In fact you shouldn't accuse someone at all. Just ignore it and move on.

Are smurf accounts allowed in Smite


Whether to display or hide user Account Balance when it is 0?

Question: The project is not related to baking directly but it is related to user payments and orders. Users can place orders and pay for the orders online. Post login, user lands on main dashboard, where pending orders, dispatched orders and other macro level information is shown. Currently account balance is not shown in this dashboard. I strongly think that it should be shown even if its 0. Other says not to show if its 0. (Its because majority of users will have mostly balance as 0.) Any rationale supporting for any of the views above? what should be done here?
Comment: Lets hope its not related to baking :-)
Comment: Is there a specific group of users that will be working with Account Balances that you could treat separately?
Comment: You cannot show nothing. Either you show $0.00 or "Free" if it's a shop-like system
Answer: You need to show the account balance when it is zero.  If a user is using the account balance feature then they're going to get really confused if it disappears entirely.
They have no way of knowing that account balance is temporarily hidden just because it dropped to zero.  They are going to spend some time hunting for their account balance and get really frustrated that they can't find it.
Also, your support personnel will most likely wind up getting calls from annoyed users who can't find their account balance.
Comment: In fact, since an account balance of $0 means that the user most likely needs to take corrective action, it is *more* important to know that your balance is $0 than it is to know it is $100.
Comment: This is the answer. It is just as important to know that your balance is $0 as it is to know it is $100.
Answer: Show it if it's ever been nonzero.
There are two competing considerations: don't hide valuable information from the user, but don't overwhelm new users with information that they are unlikely to understand. Putting these together reveals a third option: show the account balance if and only if it has ever been nonzero. This way, you progressively reveal features to the user, such as the fact that accounts have balances, without hiding information from users who already ought to understand balance. Users who have only ever used (say) the free tier of your service end up with a cleaner dashboard, while a user of paid services sees the zero balance as a signal to top up her account.
Answer: I suggest that instead, you make the account balance stand out when it's zero. Mark it red, maybe make it big. Additionally, your program should be kind enough to point out whether the balance is, or will come out to be, zero when the clicks "buy" or "add to cart."
Comment: While it's important to let the user know when they've reached zero, making it big and red it is a bit harsh.


Common but out-of-the-ordinary file formats

Question: I am wondering what some file formats are that are out of the scope of "normal" file formats you typically find on the web. The "normal" file formats I'm not considering in this post are:

Image formats like png
Video formats like mp4
Compression formats like zip
Audio formats like flac
Document formats like pdf
Source code formats like xml, js, rb, java, etc.
Plain text formats like txt
Data formats like csv

Some "out of the mainstream" file formats that I am looking for in this post are things like these (the few ones I know about):

FASTA format for nucleotide sequences
Mass Spec formats
Mol file format for 3D chemical structures.
KML and Shapefile formats
RDF and JSON-ld

Basically I just know a few file formats in the fields of Biology and GIS/mapping. A few others that might fit this "out of the ordinary" concept are SQL dumps or database dumps, or logfile formats like syslog.
I am just wondering if one could list any major common yet out of the ordinary ones (out of the ordinary mainly because they are in specialized fields), such as those from these fields, or other fields not mentioned.

Physics
Other Chemical/Biological/Genetic ones (for example, I will have to see if there are MicroArray formats, or Gel Electrophoresis)
Medicine/Hospital tools for their visualizations or records.
Point clouds
Earth science / Geology / GIS that I have missed
Astronomy data formats.
Major video/audio ones that may be easily missed (like maybe closed captioning is a format, I don't know).
Standard metadata formats (not sure about these if they are file formats yet).
Sports records.
Financial stuff formats.

Again, I'm only wondering for the major ones that are out of the ordinary that you would encounter as common in these (or other major) industries. I know there are thousands of file formats haha, so not looking for a comprehensive list or anything, just mainly want to get introduced to the major ones that are out of the ordinary but common. Instead of specific formats it could just be classes of formats too, that works as well. Thank you.
Answer: Other common GIS formats
Along with the GIS file types listed in the original question, these are (in my experience) the most common formats in which GIS data is distributed. There are many other GIS file formats, but data is usually shared in the ones listed here.
Vector Data:

MDB - ESRI personal geodatabase build on Microsoft Access Database format
GDB - ESRI geodatabase
KMZ - compressed version of KML
GPX - combination of points, tracklogs and routes created by a GPS unit
TIN - triangulated irregular network, common format for elevation data

Raster Data:

GeoTIFF - georeferenced TIFF image file - georeferencing info can be imbedded in TIFF file, or attached as a sidecar file in TFW format
ASCII Grid

Style/Formatting files (sometimes provided alongside a set of vector and raster layers):

LYR - ESRI layer file
MXD - ESRI map document

As mentioned in the comments, some of these are proprietary formats. I'm not recommending the proprietary formats, but they are the formats in which data is frequently provided. The fact that this is an open data forum doesn't change that. Fortunately many sources provide GIS data in multiple formats.
MDB and GDB can usually (but not always) be opened in an open-source program (such as QGIS or GDAL), and the data extracted and exported in a more usable format.
LYR and MXD files are often provided alongside the actual data, and it's useful to know that you can just ignore them, as they only contain style, not actual data.
Comment: 4 out of 9 isn't an overwhelming majority. Also, open-source programs such as QGIS can open MDB and GDB files.
Comment: very important to note that the overwhelming majority of these are proprietary formats; you did by noting ESRI, just wanted to make it crystal clear.
Comment: not in every instance. i've run into issues numerous times trying to convert esri data to open formats in qgis, gdal, ogr2ogr, just to name a few. four out of nine proprietary data formats, in an open data forum, is four too many.
Answer: A lot of formats are actually containers for a specific folder structure.
There are some self-contained formats like hdf5, and a lot of zip files around, including different "zip in disguise"(files that use zipping as a container for a specifically organized data structure, often with xml formatted files inside): on top of my head:
.dar files for jatsxml formatted manuscript/figures
.h5p files for the h5p format
.mbz for moodle backup files


How to convert Sketch files to a layered Photoshop file?

Question: I was wondering if there was an easy way to convert Sketch files to a layered Photoshop file? Sketch exports TIFFs, PNG and JPEG but they are all flattened. Anyone else have to do this? Any suggestions other than having to rebuild everything in Photoshop?
Comment: Hi Renee I work at Adobe and I would like to understand a bit more about how we can help. My email address is email@example.com Thanks!
Comment: If any of the answers below answers your question, please tick the "accepted"-tick-mark next to it, to mark it as the useful answers. StackExchange relies on this, and it is good for us all. If you did not get a good answer, perhaps edit your question to be more specific of what the problem is.
Answer: Try exporting the Sketch file as a PDF. Then open the PDF file in Illustrator. From Illustrator export the document as a PSD.
Sketch File Formats
Comment: That does seem to help, just very time consuming. Thank you for the suggestion. I just wish everything came with an "easy button".
Comment: That's what happens when adobe software is proprietary. They want you to work with their collection of programs.
Comment: It's the only way that I found. It's better than nothing.
Comment: Very true, it is better than nothing - not trying to complain. :) Thank you for your help, I do appreciate it.
Answer: It is very easy with Photopea:

File → Open
Choose a Sketch file.
File → Save as PSD.

I am an author of Photopea. If you have any problems, write me an email to firstname.lastname@example.com.
Comment: Comments are not for extended discussion; this conversation has been [moved to chat](http://chat.stackexchange.com/rooms/70803/discussion-on-answer-by-ivan-kuckir-how-to-convert-sketch-files-to-a-layered-pho).
Answer: As of September 2015, there is no successful way to get a layered Sketch file to work as a layered Photoshop file.
I spent some time testing with the recommendations in this thread. Going through Affinity Designer does not work either. However, I was surprised to see that .psd was available in Affinity Designer since it is proprietary.
My steps and results:

I exported my Sketch file as PDF and opened the PDF with Illustrator.

When I opened the file in Illustrator the first thing I noticed is that the Google Fonts (downloaded) I was using were garbled. I also noticed that all my text and shape layers were clip groups within clip groups within clip groups.

After reviewing the file, I then exported the opened file to Photoshop. No layers were preserved.

Long story short, .sketch to .psd doesn't work. If the developers you work with need a Photoshop file, it's time to rebuild your design in Photoshop.
Answer: Sketch is in no way compatible to de Adobe Creative Suite. Only export options that might help are SVG and PDF.

From Bohemian Coding:

Non-supported file formats for exporting:

PSD: Adobe Photoshop's file format is closed and not supported for export. If you have access to Adobe Creative Suite, you can export your work as .PDF and import to Illustrator. From there, export the project as a .PSD file.
AI: Adobe Illustrator files are not supported, but Illustrator can open .PDF or .SVG files exported from Sketch.
Comment: That did seem to help, I totally forgot that Illustrator can export to a PSD. Thank you for the suggestion.
Answer: For those who don't have access to Adobe software: I noticed that Affinity Designer does a great job of opening PDF files and exporting them as PSD. I find that editing the opened PDF (which is always necessary even if for some minor tweaks) AD is easier that Illustrator (I own and use both).
Answer: I preconize an SVG export instead of PDF. The PDF Export create lot of mask etc...
After that,

Open the SVG inside Illustrator
Select All
Ungroup ( Cmd+Shift+G ) one or more time.
In the layer local menu, decompose in layer ( sequence NOT cumulative ) PS. I don't know exactly what is the good term in english version. I use french version/
Export in PSD
Clean a little your PSD
Comment: An image could be very good to show what you mean. Please add it to your answer. And what do you mean with "clean a little"?
Comment: "Clean a little" mean : rename layers, recompose text etc. The import is not 100% clean... It's only a good basement.
Answer: Both Sketch and Photoshop support EPS files, you can try:

Export your Sketch as EPS
Open your EPS in Photoshop

Or rather than PDF use the SVG route:

Export Sketch as SVG
Open SVG in Illustrator
Export as PSD
Answer: I work on sketch a-lot but the place where I work they prefer PSD files so this is how figured it out:
1. I do work in sketch.
2. Finalize all things and when once it's done I export all the artboards in pdf.
3. Import Artboards one by one from pdf into illustrator.
4. Do not make any changes directly export to psd file.
5. Open psd file you will see all the work will be grouped into one folder and everything is masked.
6. Check every layer and folder and understand which layer belongs to which asset.
7. If there is font then delete vector mask
8. If there is any icon or any design element flatten it by pressing ctrl + e or cmd + e then delete vector mask.

I know it's a tedious task to do but I would love to know if there is any other way to do this.
Comment: There is no question Kurt here i'm sharing the steps for getting a psd out of sketch file through illustrator and photoshop
Comment: I agree, Aatur, but your last sentence seems to suggest otherwise to the casual reader. I'd advice deleting it. Thanks for understanding!
Answer:
Sketch export artboard to Pdf > open pdf in affinity designer > export document to psd... ready !!
Comment: Please explain a little bit better. Which software is used? Free? Your nearly one-line-answer is not very clear ... Welcome!
Answer: It's possible.

First, export sketch file to PDF.
Use Illustrator to open the PDF and oave it to an AI file.
Now you can export it as a PSD by using Illustrator.

The trouble is that you cannot save the PDF as PSD straight away.
Answer: I tried several methods mentioned above. The best result came from copying the Sketch Artboard to my clipboard, Creating a new document in Affinity Designer's trial version from my clipboard contents, and then exporting to PSD from Affinity Designer. It did a much better than job than the PDF/Illustrator/Photoshop methods.
Comment: I just tried this method, although this works pretty good. All of the text from Affinity to PSD will be flattened. So far, haven't seen any option to enable this.


Do acoustic or classical guitars need to be set up?

Question: Obviously acoustic and classical guitars don't have external pickups that need to be setup, but are there any other adjustments that need to be done on a regular basis?  There doesn't seem to be a bolt at the head of the guitar to adjust the neck like there is in my electric, and such.  I can't imagine that one should just do nothing and expect the neck to not warp and the guitar to play well forever.
Answer: Good question.  A nylon strung instrument exerts a lot less tension through the strings than a steel strung instrument, and as a result a well made guitar doesn't need to have the extra reinforcement in the neck of a truss rod (the job of which is to counteract the forces trying to bow the neck toward the fretboard).  Having said that, though, if your steel strung instrument needs regular adjustment to the truss rod I'd take that as a warning sign that something is not right (poor quality instrument, exposure to rapid changes in temperature or humidity, etc.)  I have a dozen or so guitars that hardly ever need any adjustment, unless I change string gauge.
In short, there are very few reasons you'd need to make adjustments - the art and science of constructing well made instruments has had hundreds of years of development, and most instruments you can buy these days will give many years of service with little or no need to tweak.
Answer: Many acoustic guitars have a truss rod that is accessed via the inside of the body of the guitar.  There are some guitars that do not have them, and there are also some acoustic guitars that have them accessible via the headstock.
Sometimes the action is so bad that sufficient adjustments cannot be made via the truss rod alone.
If the adjustments aren't too severe, shaving down the saddle can lower the action (if it is too high), and adding shims under the saddle can bring it up (if it is too low).
If adjusting the saddle is not enough, you have to do what is called a "neck reset".   This involves having a repair person remove the neck of the guitar and reshape the joint where it connects with the body.
Comment: I prefer not having shims put under the saddle though. If they don't make a firm/solid/even base under the saddle it won't transfer sound to the top as well as it should. I used to do repairs, and went through about three different saddle blanks before I got mine just as I wanted it on my D-35. The saddle material makes a difference in the sound of an acoustic too.
Answer: Yes, all guitars need to setup or adjusted over their lifetime.  Check the following and have your guitar checked out by someone who knows what they are doing if you are not comfortable:

Intonation - tune up your guitar; preferably with a decent electronic tuner.  Fret each string at the 12th fret (the notes at the 12th fret should be the same tuning).
Buzz at any of the frets
Action (string height and playability)
Quality of frets and fret wear
Comment: But how do you properly fix buzz and adjust the action?
Comment: Buzz can be cause by many different things. Frets might not be seated or leveled right. The nut or saddle might be too low. The string tension is too low to counter the built-in reverse bow of the neck. The neck's tension is too high for the strings to counter. To fix the buzz requires things like replacing the nut or saddle with one cut to the proper height or notched to the proper depth. Level or seat the frets correctly. Adjust the tension of the neck. Action is a combo of neck tension, saddle and nut height and string gauge and the pitch of your guitar. Let a repairman do it.
Answer: Proper adjustments over time will never hurt an instrument, and may indeed make them play better and last longer.  Each instrument needs to be set up from time to time, and someone who really knows what their doing and can "read" what the wood does or may do over a course of a year will provide a great instrument no matter what original condition or price was paid.  A good guitar setup is best viewed as an investment in its fulfilling life.
Often guitarists will perform these setups themselves since they know what tension or size of string they use, how they play, where they play, and what kind of buzz they can get away with (or lack there-of).  Major repairs that require special tools are often left for the luthiers and guitar techs.
There is a system in place to keep the guitar's physics from counteracting in a negative way.  This is usually, and most importantly the straightness of the neck and fingerboard and its relation to the truss rod, which as you said, has an adjustment at the headstock, or adjustment at the end of the neck near or at the neck heel.
However, with an occasional setup, and keeping the guitar comfortable (meaning, not leaving it anywhere you wouldn't want to be left) in a proper case and humidified environment it will tend to stay exactly in its happy zone for nearly the entirety of its life.  It is very much up to the owner just how far it gets out of it's happy place or not though, unfortunately.
Speaking of proper care:
I'm currently working on readjusting and resetting necks in two cheap Epiphones that were haphazardly left unattended and out of their case.  The necks or fingerboards snapped apart and the action of the strings - and therefore the delicate balance with the truss rod - had drifted to an uncomfortable zone.  And just one unfortunate event caused these guitars to significantly play worse (and therefore "harder") from where they were at before, off the assembly line.  With time, these guitars may be back to similar original condition and playable for someone who cares enough for them.


What is the Soft Question tag?

Question: What is the tag "Soft-Question" being used for?  In this field, it certainly sounds like a pejorative.  With no wiki guidance as to its use, would it be better to just remove this tag?  It seems this might be part of the external guidance/aggression we seem to be getting to ask only questions that have one and only one right answer.  For instance the Parent-Child question has been besmeared with this tag, even though it is clearly not asking for opinions or anything other than factual information.
Answer: If you are using tags as designed, there should be no soft-question tag.
Please edit it out when you see it. It's one of those "meta tags" that appears from time trying to repurpose tags to filter content beyond what the question is actually about. It's generally not useful to label questions as soft or  easy or subjective or other ways that end up misusing tags in that fashion.
For some  background, please read this post on avoiding meta tags as a matter of policy and design.
It's one of those policy decisions that I have never regretted myself, but it continues to frustrate efforts to fix things where it has been ignored.
You don't need this. Sticking to the core purpose for which tags were created is one of those policy decisions that saves us a lot of in-fighting about when and how to go outside the intended use case of a feature. And, yes, sometimes these tags are used to brand content some folks simply don't like. I would get rid of it myself.
Comment: With enthusiasm!
Answer: I agree that it gives that connotation, and that that's a bad thing. There may be some value in categorizing them somehow though. Of the questions that currently have that tag, many are about the field - perhaps we could rename it "field-of-OR".
Answer: Let me first answer the question in the title: The soft-question tag is used on some SE sites (most notably math.se and mathoverflow) and on OR-exchange to indicate that the question is not about the subject matter itself (e.g. mathematics), but about the job1 of experts in the subject matter (e.g. about doing research in mathematics). This is probably better explained in the tag guidance on MO.
So, a possible reason people may use this tag is because that is the norm on some other SE sites or OR-exchange and that they are used to that. I do not think it is seen as prejorative on those sites. (Clearly, people appreciate them enough to vote and answer!) However, that it is being used on other sites is in itself not a good reason to use them here and I agree with Robert that they in principle should not be used.

But I'd like to point to the other answer on the question Robert linked to, to note that there are some meta tags that are actually used without too much issues on some sites.
From what I can see, the meta tags that are purposefully kept on some sites mostly are used to unambiguously indicate the type of answer requested. Some examples are the beginner tag on Code Review and the self-study tag on CrossValidated. These tags are useful, in the sense that there certainly people who are more skilled or more interested in either teaching people beginning with a particular programming language, who then are happy find those questions by following this tag. (See also this 'defense' of the beginner tag)
However, the tag 'beginner' is also dangerous. If people start slapping 'beginner' on every question they think is easy, you'll end up with endless bickering on those questions. How can we get the benefits of a meta-tag without the crippling disadvantages?
I'm not sure what is sufficient for that, but the following seems at least nessecary to me:

It should be clear and unambiguous when the tag must be used. Note the use of 'must': while the applicability of normal tags can be fuzzy, whether meta tags should be used must always be clear. If it is not clear from the question whether it is a 'beginner' question, then that should be clarified, likely by asking the asker. This also means that a 'beginner' tag should not be applied by someone other than the asker unless the asker has explicitely stated that they are in fact a beginner in that particular language.
It should be clear and unambiguous what a tag means. This is mostly to prevent discussion on answers of the question about whether the answer is appropriate for questions within the tag.

Perhaps more succinctly, if you really want to use meta-tags, be sure to design them such to avoid all discussion about whether a meta-tag applies to any particular question, or what behaviour is expected for questions tagged as such.

1: 'job' here means the activity experts in the field do, e.g. research. This includes doing this activity if you're not getting paid for it.
Answer: On OR-Exchange, the soft-question tag was used for questions which were expected to produce answers that are either not strictly mathematical or more, well, opinon-based. Generally speaking, those kind of questions were welcome -- if tagged as such.
While Jeff Atwood is not a big fan of such "meta-tags", the soft-question tag still is heavily used on various SE sites, for instance:

MathOverflow: "Questions that are about research in mathematics, or about the job of a research mathematician, without being mathematical problems or statements in the strictest sense. In other words, questions that can be answered without making computations or applying theorems and axioms."
Math.SE: "For questions whose answers can't be objectively evaluated as correct or incorrect, but which are still relevant to this site."
TCS.SE: "A soft question is a question (possibly subjective) about the field of theoretical computer science as opposed to being a question in theoretical computer science."
Comment: I don't really think Jeff's opinion holds much sway anymore. His arguments are of course relevant, and a lot of meta-tags do have a lot of the problems described. In any case, the soft-question tag is completely unusable and incomprehensible without a proper explanation of what it means or when it should be used.

What is the Soft Question tag?


Paper wallet imported to blockchain.info with private keys

Question: Recently I added my paper wallet address and private key to my blockchain.info account. Now I cannot find an option in the app or in the website to delete the imported private key, does that mean that blockchain.info now holds my private key? In that case, I won't be able to add my wallet into another similar app because it's already synced with blockchain.info with my private keys! I am new to this whole bitcoin thing so I am still trying to figure things out.
Regards,
Bince
Comment: No point of asking for deletion. Consider it compromised and move your funds to a new wallet.
Answer:
does that mean that blockchain.info now holds my private key?

Yes, but not exclusively. You still have your private key on paper, so you still hold it. If you don't (i.e. you lost your paper wallet or destroyed it), you can still get your private key from blockchain.info.

In that case, I won't be able to add my wallet into another similar app because it's already synced with blockchain.info with my private keys!

No, that is not how Bitcoin works. Anyone who holds the private key can spend your Bitcoin. You also hold it on your paper wallet, so you can still import it into another wallet software. There is nothing that prevents you from doing that; it's not like something that can only be imported once.
If you don't want blockchain.info to have your private key, just make a new paper wallet and send your Bitcoin there from blockchain.info. If you want to access your Bitcoin from a different wallet than blockchain.info, then just import your private key into a different wallet.
Answer: The private key is a 256-bit integer used to generate a public key. A bitcoin wallet address is a hashed version of your public key.
The private key allows you to sign transactions (send BTC to another address).
With the private key of a given address you can sign any transaction, anywhere.
That means that if you have that private key, you can use it in any wallet. Although blockchain.info stores your private key now, you still have it, so you can import it on any other wallet.
Answer: The safest possible thing you could do is to send the money from your blockchain.info wallet to your local wallet in a normal Bitcoin transaction.  This might be a few bucks, but it is worth the peace of mind.
You could delete your blockchain.info account and then open another one if you like, but this is no guarantee that they will delete your private key.  I advise sending an email to Blockchain.info asking what their policy is on keeping and removing private keys.
In general, it is best not to import private keys from wallets that you do not have full control over.  You don't know what they are going to do with your private keys and the sure fire way to safeguard your money is to just send it to a wallet you have FULL CONTROL OVER using a normal Bitcoin transaction.


Raspberry Pi Boot USB Flash Drive Automatic Image Backup

Question: I boot Raspberry Pi's from USB Flash Drives and have been trying to utilize the bkup_rpimage found on GitHub.  I changed the drive to point to the USB Flash Drive in the bkup_rpimage.sh file; however, please note that the comments referring to the SD card were not changed in this file.  I have used the exact model and size of the boot USB Flash Drive and, also, used the same model USB Flash Drive that doubles the size of the boot USB Flash Drive.   The same errors (below) were generated for both USB Flash Drives when the backup script was run.  Is a larger USB Flash Drive required?  Any help with solving this will be appreciated.
Errors generated with sudo sh bkup_rpimage.sh start -c /media/pi/BACKUPDRIVE/rpi_backup.img
trap: SIGINT: bad trap
-e Starting SD Image backup process
-e Attaching /media/pi/BACKUPDRIVE/rpi_backup.img to /dev/loop0
losetup: /media/pi/BACKUPDRIVE/rpi_backup.img: Warning: file is smaller than 512 bytes; the loop device may be useless or invisible for system tools.
partx: /dev/loop0: failed to read partition table
-e Mounting /dev/loop0p1 and /dev/loop0p2 to /mnt/rpi_backup.img/
mount: special device /dev/loop0p2 does not exist
mount: special device /dev/loop0p1 does not exist
-e Skipping rsync since /mnt/rpi_backup.img/ is not a mount point
-e Flushing to disk
-e Unmounting /dev/loop0p1 and /dev/loop0p2 from /mnt/rpi_backup.img/
umount: /mnt/rpi_backup.img//boot: not mounted
umount: /mnt/rpi_backup.img/: not mounted
rmdir: failed to remove '/mnt/rpi_backup.img/': Directory not empty
-e Detaching /media/pi/BACKUPDRIVE/rpi_backup.img from /dev/loop0
partx: specified range <1:0> does not make sense
-e SD Image backup process completed.

Answer: If you are copying the error verbatim, you are not providing the correct location to save the image file. /media/pi/BACKUPDRIVE/rpi_backup.img will need to be changed to an existing directory where you want the file created


Difference between colloid thrusters and electro spray thrusters

Question: What is the difference between colloid thrusters and ion electro spray thrusters
Answer: They appear to be two names for the same thing. See http://lmts.epfl.ch/MEMS-ion-source, for example.
Comment: Link seems to be broken, a good example of why link-only answers are discouraged.
Answer: According to the Wikipedia article Colloid thruster they are the same thing:

A colloid thruster (or "electrospray thruster") is a type of low thrust electric propulsion rocket engine that uses electrostatic acceleration of charged liquid droplets for propulsion. In a colloid thruster, charged liquid droplets are produced by an electrospray process and then accelerated by a static electric field. The liquid used for this application tends to be a low-volatility ionic liquid.

The Wikipedia article includes a link to some MIT lecture notes for Aeronautics and Astronautics; On the Lecture notes page for 16-522-space-propulsion-spring-2015 one can find MIT16_522S15_Lecture22-23.pdf, the title of which is:

Session  : Cone-jet Electrosprays, or Colloid Thrusters

These two terms indeed seem to be use interchangeably.


How would Jacob have offered a tithe?

Question: In Genesis 28:22 Jacob makes a vow including a promise to give God a tenth (tithe) of whatever God gives to Jacob. Earlier we see Abraham give his tenth to the high priest of Salem, Melchizedek. And later, of course, a tithe is given to the Levites. But how was Jacob to give a tithe to God since there were no priests yet in his day?
Comment: While I agree with both [Sarah](http://hermeneutics.stackexchange.com/users/2027/sarah) and [gideon marx](http://hermeneutics.stackexchange.com/users/2714/gideon-marx), we have to note that God had just promised Jacob and his descendants the land he was lying on. Therefore a tenth of the land would have been part of the vow. It was not until centuries later did Jacob through his descendants possess the land so God can then *demand* the tithe as a debt payable. This is the reason God considered the tithe as a vow (Lev 27).
Comment: If there was a priest in Abraham's day (Melckizedek), why assume there was not one in Jacob's day?
Comment: Hebrews 7:1 For this Melchizedek, king of Salem, priest of the Most High God, who met Abraham returning from the slaughter of the kings and blessed him,
2 to whom also Abraham gave a tenth part of all, first being translated "king of righteousness," and then also king of Salem, meaning "king of peace,"
3 without father, without mother, without genealogy, having neither beginning of days nor end of life, but made like the Son of God, remains a priest continually.
Answer: It seems likely that Jacob would have given the tithe to God as a burnt offering. In the modern world, we are accustomed to thinking of tithes in terms of currency, but in the ancient Near East, the tithe came from the produce of the land:

You shall tithe all the yield of your seed that comes from the field year by year. And before the LORD your God, in the place that he will choose, to make his name dwell there, you shall eat the tithe of your grain, of your wine, and of your oil, and the firstborn of your herd and flock, that you may learn to fear the LORD your God always.
Deut. 14:22-23 (ESV)

Specifically, in Jacob's case, his wealth is in the form of flocks. We see in Genesis 30-31, that God conspires against Laban to increase the wealth of Jacob by making Jacob's flocks grow. And it is from these flocks that he would have tithed. The customary way of doing so was through making an offering. We've seen already in Genesis the example of Abel in this regard:

Now Abel kept flocks, and Cain worked the soil. In the course of time Cain brought some of the fruits of the soil as an offering to the Lord. And Abel also brought an offering—fat portions from some of the firstborn of his flock.
Gen. 4:2-4 (ESV)

While Abram did give the tithe to Melchizedek, Abel and the Patriarchs in Genesis are shown having unmediated access to bring offerings before God (cf. Gen. 35:14). Given that in making his vow Jacob builds an altar, this is likely the means by which he intends to give a tenth to God.
Comment: You've been thinking about this one a while. :) On the line you take here, see also the 4th edition of [Franz Delitzsch's Genesis commentary, p. 167](https://archive.org/stream/newcommentaryong02deli#page/166/mode/2up) (1889), and the cross-reference to [Leviticus 27:30-33](https://www.biblegateway.com/passage/?search=Leviticus+27%3A30-33&version=NIV;WLC) in particular.
Answer: Before we can determine just how Jacob would pay his tithes, we have to examine the entire context of the passage.(Gen. 28:17-22)

And he was afraid, and said, How dreadful is this place! this is none
  other but the house of God, and this is the gate of heaven.
  18 And Jacob rose up early in the morning, and took the stone that he
  had put for his pillows, and set it up for a pillar, and poured oil
  upon the top of it.
  19 And he called the name of that place Bethel: but the name of that
  city was called Luz at the first.
  20 And Jacob vowed a vow, saying, If God will be with me, and will
  keep me in this way that I go, and will give me bread to eat, and
  raiment to put on,
  21 So that I come again to my father's house in peace; then shall the
  LORD be my God:
  22 And this stone, which I have set for a pillar, shall be God's
  house: and of all that thou shalt give me I will surely give the tenth
  unto thee

Jacob sets his head down in a particular place, upon a rock, and he discovers that God is in this place and angels are ascending and descending. He then declares,"

And he was afraid, and said, How dreadful is this place! this is none
  other but the house of God, and this is the gate of heaven(Gen. 28:17)

So the context is the House of God, which would become the physical Temple. It is to the Temple that the tithes are paid; and where the storehouse is kept.(Mal. 3:10)

Bring ye all the tithes into the storehouse, that there may be meat in
  mine house, and prove me now herewith, saith the LORD of hosts, if I
  will not open you the windows of heaven, and pour you out a blessing,
  that there shall not be room enough to receive it.

Jacob's vow must be understood as more than an obligation: it is the promise of blessing that a Covenant God made with Abraham, confirmed through Isaac, and now he was the next in line to whom "All the families of the earth will be blessed".(Gen. 12:3)
The tithe is to be understood as part of our worship (Gen. 14:20),

And blessed be the most high God, which hath delivered thine enemies
  into thy hand. And he gave him tithes of all

Following Jacob's vow, he departed for Syria, where Laban, the brother of Rebecca his mother was. And after he came back, he was reminded by God of his vow(Gen 35:1), and he built an altar (Gen.35:3) :

And Jacob set up a pillar in the place where he talked with him, even
  a pillar of stone: and he poured a drink offering thereon, and he
  poured oil thereon.
  15 And Jacob called the name of the place where God spake with him,
  Bethel

The tithe is the physical action in our worship to God, in honor of His Blessing and Provision in our lives. It doesn't exist as a separate act, but it is part of our response to God. That is why the tithes were to be "brought to the storehouse"(Mal. 3:10), it is the place in the Temple where the tithes were kept and to be distributed.
Jacob's act of building an altar, and later, pouring out offerings and making sacrifices on that altar, are a precursor to the "tithes" he would pay through his children, and later, his children by faith-who "rest" upon the Rock that Jacob had lain his head.
.
Answer: Jacob did not offer tithes. He offered alms.
The tithes were offered in the covenant of Abraham (Gen 14:20). Remember that God made a covenant with Abraham and his son Isaac.
Abraham's covenant was of circumcision-(Gen 17:7-13)
The next covenant was made between God and Isaac.
The everlasting covenant. (Gen 17:19)
We are under the everlasting Covenant. We offer alms.
Acts 10:4
And when he looked on him, he was afraid, and said, What is it, Lord? And he said unto him, thy prayers and thine alms are come up for a memorial before God.
Alms- Food, Clothing, and Shelter, and let money be a last result because you are trying to get them dependent on money.
Comment: Welcome to BH.SE! Please [take the tour](https://hermeneutics.stackexchange.com/tour) to get a feel for how the site functions. What you are saying here is contrary to both the Hebrew and the Greek (LXX), both of which refer to Jacob's vow as a tithe, viz עַשֵּׂ֖ר אֲעַשְּׂרֶ֥/נּוּ ("tenth part tithe of us I will") / δεκάτην ἀποδεκατώσω αὐτά ("tenth part tithe I will).
Answer: There is no record of Jacob fulfilling his vow to give God a tithe. So any answer as to how (or if) the vow was fulfilled involves conjecture.
At the time Jacob made his vow he had neither children nor flocks. When he returned to the place where he made his vow he had eleven sons, one daughter, and many animals. When Jacob returned to Bethel he only made a drink offering:

And Jacob set up a pillar in the place where he had spoken with him, a pillar of stone. He poured out a drink offering on it and poured oil on it. (Genesis 35:14 ESV)

One could conclude Jacob never gave the tithe he promised.
However, his youngest son at that time was Joseph. Later God would use Joseph for good:

As for you, you meant evil against me, but God meant it for good, to bring it about that many people should be kept alive, as they are today. (Genesis 50:20 ESV)

Joseph was taken for service to God. While not quite a "tithe" (Joseph was 1 of 12 children at the time Jacob returned), if Levi, the future priestly line, and Dinah (the only daughter) were excluded, Joseph would be one of the remaining 10 sons. In this sense God fulfilled Jacob's promise to tithe by taking Joseph away from Jacob for His purposes in Egypt.
Answer: Tithe in my opinion should be given to the poor, because if we give to the poor it's one way of giving to the living and everlasting God as the apostle  Paul tought in the book of Hebrews 7
Comment: Welcome to the site, Katende. You might like to check out our Code of Conduct for this site, as just giving one's personal opinion is unsuitable by way of an answer. Reference to Hebrews 7 is not related to the question and the verses asked about. Geneses 28:22 needs to be explored in depth, along with the matter of priests in Jacob's time. If you can do this and then add relevant facts to your answer, that would be good.
Answer: Jacob paid tenth of all things he earned and possessed to God El Elohim, through his priest malkizedec. God blessed him with abundance in all his endeavour. His faithfulness behaviour in his vows led him to wrestle with God and receive the great inheritance of his father Isaac.
Comment: Hello Aashish, welcome to BHSE, so glad to have you with us! If you haven't already, make sure to take our tour to get yourself familiar with this site, you'll discover that we are a little different than other sites you know. (hermeneutics.stackexchange.com/tour) Thanks!
Answer: Please why do preachers only concentrate on tithe according to Malachi, failing to consider salvation first, tithing is a vow (in the case of Jacob) and Abraham never gave from his sheep or cattle to Melchizedek but from the spoils and even Melchizedek the priest rejected the spoils and asked Abraham to keep it and give him men either (Genesis 14:14-27). Note there was no percentage he gave him all and in the book of Deuteronomy 12:5-8 tithe was not given to a priest. Look at the book of Numbers 18:20-26, the law God gave to Moses about the Levites was that they should not have any inheritance but don't preachers leave an inheritance for their family?
Read the book of Numbers 18:28-32 and read Deuteronomy 14:22-30. We are meant to take our tithes to a place chosen by God and eat and be happy or sell it and turn it into money and go to the chosen place and eat and drink. Let preachers stop making believers feel they would die if they do not pay tithes.
Comment: Welcome to Biblical Hermeneutics.  When you have a moment, please take our Tour to see how we are different to other sites: https://hermeneutics.stackexchange.com/tour
Answer: Tithe is not limited to giving to the Levites and not only priests received tithe. Deuteronomy 14: 28 - 29 talks about the 'poor tithe'. It is more likely that Jacob started giving to the poor than looking for Melchizedek. After the destruction of the Temple, tithe went to the poor as it must have been in the time before the priesthood.

How would Jacob have offered a tithe?


When will my new license appear in the FCC database?

Question: I tested and passed my Technician's test on Thursday, June 4, 2015. Approximately how long will my license take to appear in the FCC database?
Answer: Congratulations!
This depends on the folks that gave you your test (Volunteer Examiners, or VEs), the organization they are working with (ARRL?), and the FCC (if you're in the US). A bottleneck anywhere can make it take up to a couple weeks, but likely you'll have a call sign about a week after the VEs submit your paperwork. Your best bet would be to ask them, though, as they will know if there are local factors.
You can search the FCC license database with your name to see if you've been assigned a call sign. I have no idea how long it will take for them to (presumably) email your license, as they no longer mail out paper licenses like I got, but once you have a call sign you're legal to operate.
Comment: The FCC will send a notification e-mail only. You get the watermarked (Original Copy) PDF file when you log in to your FCC ULS account. Anyone can get a Reference Copy, aptly watermarked, of your license though without logging in the FCC ULS system.
Comment: I don't think they email the license at all, I think you just have to search the FCC database, that's all.
Comment: I think I heard the emailed license is new since they dropped the paper ones.
Comment: I got my call sign from the VEC rep (who was present at the exam session -- they commonly aren't) the evening of the business day after the session, and the email from FCC with the link to the printable license the day after that.  My call showed in the database the first time I thought to look, a couple days later.  Any further delay is due to your VEs and/or VEC.
Answer: Let's say you pass your ham test on a Monday Morning,
The VE who handles submitting info to the FCC submits it the same day online.
If it's 12:40 P.M and the VE files it online. It is processed by the FCC's "Automotive" Grant system. There is no one who approves it; It's automatically approved by the system. The License Grants the moment it's filed. The FCC's website Refreshes every hour, and posts your call sign to your FRN accordingly.
It's not a matter of FCC Holidays delays to weekend delays. The speed of your Grant depends on the Speed of the VE to file yours and everyone else's info, if they have passed.
Most of the time, the Trustee will be lazy and just have the paperwork with them in their vehicle to take home to file later on. Normally, You can expect them to file your and everyone else's info online in 1-3 business days, When one finds time to do it.
FCC Statement: It's not a Matter of National Holidays or Weekends that delay the Grant speed. Its the VE who has control!
Once Your info is filed online, the Automotive FCC system automatically Grants and posts to your FRN. The FCC data base refreshes every hour, as previously mentioned.
If anyone told you it refreshed daily at midnight or 2 A.M or 6 P.M, like i've read online.... that's 100 percent incorrect!
The system refreshes every hour!
Here's what you can expect!
Ninety percent of the time you will get your license granted 1-4 days after testing depending on the VE's filing speed.
It's "almost" unlikely that the trustee will file your info online by the 5th, 6th, or 7th day, Yet there are some lazy people who think they can do it whenever because they know they have 20 days before people can call the FCC asking questions or complaining.
Ten percent of those who don't get their license by the 7th day or later will most likely receive it by the 14th-20th day after testing
Because.....  Let's say you live in California:
to Mail a letter to Washington DC would take a couple more days than a letter being sent from, let's say, Texas or Florida.
Also, take note that, If your forms were mailed out by paper... Then the FCC has to Manually Process your info, and this takes a bit more time when they receive stacks of letters to sort threw. If your mail arrives at FCC headquarters, it can be there for days before someone gets to it and processes and posts it on the ULS.
There is a big reason why E-Filing Saves the FCC time and money, and for the convenience of the person who passed the exam to get on the air faster.
If you're still waiting and its the 9th-12th day....Expect it no faster than the 14th day,
and don't expect it no longer than the 20th day to be posted!
If you don't see your license posted on the FCC's website with your FRN number, Contact them for help as there may be an issue.
Also, i know this may not be helpful but, if you know the VE and they do not like you from past GMRS experience, they will diffidently hold your file or send it by mail to give you a hard time. This happened to a friend of mine.
If you are on the 10th day, i would just go ahead and stop checking online because it's most likely not going to post until the 14th Business day, not including weekends because it's most likely sent by mail, and they can't process on weekends manually.
Also, I would go ahead and use the time your waiting to just start studying for your General License, So you're able to use your Technician license till the General -- it just updates your FRN and license info.
I hope this helps, I have a friend who works the DEPT inside Filing and Amature HM DPT
Good luck
Till Then.... 73'z
Answer: The processing times will probably vary. It took 1 month for my call to appear on the FCC website. (My exam was conducted by the Volunteer Examineers from Yokohama, Japan)
If the e-mail address field in your FCC ULS entry or NCVEC QUICK-FORM 605 is filled-up, then an e-mail notification will be sent. The NCVEC QUICK-FORM 605 is the form you fill up prior to taking the exams with your chosen VE.


Share folders between users

Question: I would like to share my "Videos" folder with another user on the same computer. I created a group to which I added the folder as well as both the users. However, when I log into the other user, I still cannot view the contents. Any idea how I can do this?
Answer: welcome to the Elementary OS forum!

Since you have already created the group "share" and you are confident that both accounts are members of the group "share" then setting the POSIX permissions are relatively straight forward.

1. Go to Applications -> Terminal (or Win+T)
2. In Terminal type: cd ~
WARNING: The next two commands use the recursive flag!  This means that the command will set the owner and group (then the file permissions) from that point down.  Please follow all instructions carefully...
3. Type: sudo chown -R rahul:share Videos
NOTE: You will be prompted for your login password.
I included the username from your screen shot.
4. Type: sudo chmod -R 775 Videos
NOTE: This will give full read, write and execute permissions to your rahul account and the "share" group.
5. Type Cont+D to exit the Terminal.

At this point, you and anyone in group "share" will have full access to rahul's Videos folder.  Furthermore, anyone in the "share" group will be able to make changes (add, edit or delete) files from rahul's Videos folder.

Good luck.

Share folders between users


ASP.NET Web Development Server

Question: Can someone explain how the ASP.NET Web Development Server work? I don't have IIS installed on my development machine. So Visual Studio 2008 is debugging my web app project in the built-in web server. I want to know where do all the files get deployed to for debugging. Is there any folder similar to \inetput\wwwroot? Thanks.
Answer: The web server is an executable file named WebDev.WebServer.EXE and located in \WINDOWS\Microsoft.NET\Framework\v2.0.50727. When debugging the web site, Visual Studio starts up an instance of the application with the following parameters.
WebDev.WebServer.exe \port \path [\vpath]
This ASP.NET Development Server simply uses the compiled web application in the debug folder, which is provided as /path, to serve the website.
You can read more about this here.
Answer: Do a search for a folder called "Temporary ASP.NET Files". This is where files are precompiled and temporarily deployed/stored for the development server (Cassini) to serve them up.
On my machine, the directory is C:\WINDOWS\Microsoft.NET\Framework\v2.0.50727\Temporary ASP.NET Files, and it is currently over 260MB.
Answer: It uses your /bin dir for the assembly and your aspx files for the aspx files. The files aren't really deployed, they are just assembled/compiled and then the local web server uses them.
Answer: The files don't get deployed at all. The Web Development Server (often called Cassini) binds directly to the website or web application folder.
Comment: How do you figure?  The files have to get precompiled somewhere!

ASP.NET Web Development Server


CBM PET 2001 garbled screen

Question: I picked up this PET and trying to restore it. Screen is garbeled on boot and stays like that displaying random chars, some of them flashing. Tried to resocket the chips, but it didn't help. I don't have a logic analyzer, and ram chips are not socketed. What sort of checks I can I do to identify the fault? I have a multimeter and osciloscope, not very skilled at electronics, though.
Comment: If / when you get it working, it would be great if you updated this question with what the actual problem turns out to be.
Answer: The garbled screen is normal on startup, but should be replaced by the BASIC screen after a moment.
There's a rather detailed troubleshooting guide, including links, at http://www.dasarodesigns.com/projects/troubleshooting-common-problems-with-the-commodore-pet-2001/
I'd suggest that you ignore the spare parts sales pitch at the beginning and work your way through it.
You might also want to have a look at the Tynemouth Software PET repair blog entries at http://blog.tynemouthsoftware.co.uk/ -- they show fixing some interesting PET issues step by step.
Comment: @tofro Fair enough, but then, the question is too broad to have a short, specific answer, so pointing the person asking to existing troubleshooting guides, be it on paper or online, is the best one can do. If you're concerned about link validity: The page in question has been archived by the Internet Archive, and I trust everyone on this Stack Exchange to be able to use that.
Comment: The question isn't too broad, but there's a fairly lengthy set of diagnostics that you need to go through to find out what's wrong. Bad/failed RAM is most common, but ROM failures, PCB corrosion and many other causes plague older CBM machines. (As an aside, I'd heard rumours of PETs with drilled-out PCBs to prevent upgrading memory to force buying a new computer, but this photo shows it off clearly)
Comment: I'm afraid that, other than the first sentence, this is a link-only answer. It might be helpful, but only as long as the links remain valid.
Comment: In this case, your answer should have been a comment.
Comment: If the question is too broad, it should be closed as such so it can be fixed before it's answered.
Answer: This is anecdotal, so take with a big grain of salt...
I have a C-64 power supply that was home-brewed for me by my Dad when I was a kid from the remnants of the original.  My Dad, never being one to do anything halfway, did a fantastic job and added a 'voltage adjust dial' and analog meter to the finished supply.  This means I can actually dial-down the voltage to my C-64 until the computer does _weird things_™.
Not that I do this on purpose, but occasionally the dial gets bumped and the volts go low and the C-64 breaks out into a screen of gobbledy-gook that looks almost exactly as you describe.
I'd check the power supply first thing and make sure there are enough jolts going to the main board.
Comment: I don't throw very much away in terms of tranformers.
 Now I have a pile of transformers with no inkling of what each one was originally for.  Basically if the connector, voltage and ampage match, I use it.
Comment: Yep.  Always a good idea to keep the old wall warts.  I have a tub of them myself. - But the OP question immediately made me think of what my 64 looks like when it's under-powered.

CBM PET 2001 garbled screen