What are the very fundamental differences in architecture between Unix and Linux? I watched a short intro to Unix from the 70s (  3D animation starts at 1:56), at the end the general tripartite architecture of Unix was displayed as a 3D animation. Because I have seen already diagrams of the ovarall Linux architecture, I became confused.  Both diagrams, Unix and Linux, share the Kernel, but then Unix is wrapped by the Shell and the Shell by the Utilities. Linux instead is only wrapped by the Userspace, and the Shell does not wrap anything but is just one of many processes within the Userspace.  How do Unix and Linux differ on a very basic level, what do they have in common ? Why is Unix tripartite and Linux two-layered ?  Is a Shell a complete different concept within Unix than in Linux ?
Is Linux a Unix? So, there are lots of different versions of Unix out there: HP-UX, AIX, BSD, etc. Linux is considered a Unix clone rather than an implementation of Unix. Are all the "real" Unices actual descendants of the original? If not, what separates Linux from Unix?
May I use a question mark in the middle of a sentence? Examples:  Would you like the drapes to be white? or perhaps something off-white? Would you like the logo to be centered? at the bottom? left off entirely? When I have my external monitor hooked up, I access it by mousing off the left hand side of my Macbook display. Can I switch this so that I can access the external by mousing off to the right of My Macbook display?   The reason I ask, is my monitor is on the right side of my macbook, and it's unintuitive to mouse left to get to a screen on the right. Recommended way to save uploaded files in a servlet application Uniform vs discrete Gaussian sampling in Ring learning with errors The Wikipedia article on  mentions two methods of sampling "small" polynomials namely uniform sampling and discrete Gaussian sampling. Uniform sampling is clearly the simplest, involving simply uniformly selecting the coefficients from the set of small coefficients, thereby guaranteeing they will be small. However, the articles mention that security proofs rely on discrete Gaussian sampling.  However, I have a bit of difficulty wrapping my head around    Why discrete Gaussian sampling would be better than uniform, security-wise?   I mean, usually uniform is preferable - it maximizes the entropy/information in each sample, making the outcome more unpredictable. I could understand it if the Gaussian sampling technique would somehow serve to avoid (at least with high probability) "weak" parts of the space of outcomes but I have found no information/justification that this is the case.  Another reason I can see why discrete Gaussian might be better is that there is, after all, a chance (albeit a small one) one would select a non-small coefficient, so the space of outcomes is actually larger. However, given that this probability of hitting this extra space is (by design) quite small but also that one would likely immediately reject such a sample (because the algorithm calls for a small polynomial), this seems to be irrelevant.  It is not because I am against discrete Gaussian sampling I just want to understand why it is more secure. Also, I want to understand if it really IS more secure or it is simply easier to prove security in that model. I would actually consider that very interesting if it is the case because it raises the question of why is it easier to prove the security under conditions that are intuitively worse (i.e. discrete Gaussian vs the intuitively better uniform case)? If it is so intuitively clear that uniform sampling is better, surely it must be possible to transform that intuition into a security proof of RWE also under uniform sampling. Otherwise, I would fear the intuition must with high likelihood be wrong or at least dubious. How can I find out which apps I have already downloaded on my iPhone? When you attempt to download an app that costs money, you will not be charged if you already bought the app. After you press buy and enter your iTunes password, it will say "You have already purchased this item. To download it again for free, select OK."  The problem is that I deleted hundreds of apps from my phone, some of which were paid for. Later on I might find an app I like but notice that it costs money. It might be an app I had already paid for, or an app which I got when it was free.  How can I know if I tap the buy button if I will be charged for the app or not?  In other words, how can I know if I owned a previous version of an app before? I can't seem to work out the inequality $(\sum |x_n|^q)^{1/q} \leq (\sum |x_n|^p)^{1/p}$ for $p \leq q$ (which I'm assuming is the way to go about it). How would I implement the quantum oracle in Deutsch's algorithm? Is the harmonic oscillator potential unique in having equally spaced discrete energy levels? I'm flying Etihad Airways to Melbourne and I've a 14 hours layover at Abu Dhabi.  Some say that as long as you are inside the airport terminal you don't require a transit visa while some say you need a transit visa if your layover is more than 10 hours.  Can I stay inside the airport without a transit visa? Rules for Profiles Are there any rules concerning what I can put in my profile? Let $x_0 \in \mathbb{R}$ and $f,g: \mathbb{R} \to \mathbb{R}$  such that $f$ is discontinuous at $x_0$ but $g$ is continuous at $x_0$, then $f+g$ at $x_0$ is...   My approach: After some graphical attempts to construct such a pathological case as given above I claim that the described scenario isn't possible. That is $$f \text{ disc. at } x_0 \text{ and } g \text{ cont. at } x_0 \implies f+g \text{ disc. at } x_0 $$  Proof: I was trying to come up with a contradiction, because if they happen to work out I find these kind of proofs to be most satisfying.   Assume $f+g$ is continuous at $x_0$ that is $$\forall \epsilon &gt; 0 ,\exists \delta_1 &gt; 0 : \forall x \in \mathbb{R}, |x-x_0| &lt; \delta_1 \implies |f(x)+g(x)-f(x_0)-g(x_0)| &lt; \epsilon  $$  Since this statement must be true for all $\epsilon &gt; 0$ I could choose $\epsilon:=1$. Next I know that also $g$ is continuous at said point $x_0$, thus  $$\forall \epsilon &gt; 0, \exists \delta_2 &gt; 0 : \forall x \in \mathbb{R}, |x-x_0| &lt; \delta_2 \implies |g(x)-g(x_0)| &lt; \epsilon $$  and I have that $f$ is NOT continuous at $x_0$ therefore: $$\exists \epsilon^* &gt; 0, \forall \delta&gt;0: \exists x \in  \mathbb{R}, |x-x_0| &lt; \delta \wedge |f(x)-f(x_0)| \geq \epsilon $$  My problem is to bring all these three statements nicely together. Mainly I get confused by the quantors. In order to match all three statements I assume I have to choose $\epsilon &gt; 0$ such that the last statement is met, so say $\epsilon:= \epsilon^*&gt;0$, so statement 1 and 2 are still true for said $\epsilon$  I also need to choose $\delta$. Lets say $\delta = \min{(\delta_1,\delta_2)}$ now I should be able to work with all three statements at the same time right? But then I stumble with my argumentation.  Let $|x-x_0|&lt; \delta$, then we obtain $$ |f(x)+g(x)-f(x_0)-g(x_0)| \leq |f(x)-f(x_0)| + |g(x)-g(x_0)| &lt; - \epsilon + \epsilon =0 $$ which means that $|f(x)+g(x)-f(x_0)-g(x_0)| &lt;0$ and I hope that this is a contradiction because $|.| \geq 0$. Please comment (or answer) if I am right or absolutely on the wrong path. I'd also appreciate it if you criticize my formulation. Priority and timing between enchantments and instants If I have priority and cast an  on a just summoned 2/3 creature, then, passing priority, my opponent casts a  on that creature, does my creature survive? The first spell that resolves is obviously the bolt, that deals 3 point of damage to the creature; but immediately after, will the  Unholy Strength resolve (giving +2/+1), allowing the creature to survive? "I left smoking", "I quit smoking", "I gave up smoking", "I stopped smoking" are these same? For various such sentences in many cases I get confused, it seems different for different cases. I want to know if someone left doing something for permanantly then what should be used? Also give some examples for different cases. Suppose... "I left my bag" means "I forgot my bag". but If I want to say the same for permanentaly "I left bringing my bag". Where should we use "stop" and "quit" then? Beamer: How to Disable `\pause` Temporarily Given the case I made two independent changes in one file: eg. added a new method and changed another method.  I often don't want to commit both changes as one commit, but as two independent commits.  On a git repository I would use the Interactive Mode of  to split the hunk into smaller ones:   git add --patch   What's the easiest way to do this with Subversion? (Maybe even using an Eclipse plug-in)  Update: In , Ryan calls it: “The Tangled Working Copy Problem.” Access Java / Servlet / JSP / JSTL / EL variables in JavaScript Why does a proof of $\exists f: X\to Y$ injection $\iff \exists g: Y \to X$ surjection requires the axiom of choice? Why does a proof of $\exists f: X\to Y$ injection $\iff \exists g: Y \to X$ surjection requires the axiom of choice?  This question is answered here:   I'm not interested in a proof itself of this theorem, I want to know why this requires the Axiom of Choice. Why is there an electric field in a wire even though it is a conductor? If you take a perfect conductor, there cannot be a field across it since if there were, the particles would arrange themselves in a way to cancel out the field right?  Yet, why does the same not hold true for a wire. A wire is essentially a long, thin conductor yet electrons do indeed flow so there must be an electric field.  Does this not contradict with what happens in a conductor? Why don't the electrons re-arrange to cancel out the electric field? Piping STDERR vs. STDOUT According to "" (pg. 44), you can pipe only STDERR using the |&amp; redirection symbols.  I've written a pretty simple script to test this:  #!/bin/bash echo "Normal Text." echo "Error Text." &gt;&amp;2   I run this script like this:  ./script.sh |&amp; sed 's:^:\t:'   Presumably, only the lines printed to STDERR will be indented. However, it doesn't actually work like this, as I see:      Normal Text.     Error Text.    What am I doing wrong here? The Problem  Currently if I flag a post, I cannot check the status of the flag unless I have prior helpful flags. This means, for example, that a new user who wants to check the status of his first flag cannot do so while it is pending (active).  This feature request is based on my experience on MSO, where I wanted to check the status of my flag but could not get to the summary page without cheating (tweaking my SO link to work with MSO). It also stems from this question, where the OP indicates he had the same issue:   My Proposal  If I have flagged any post, then show me a "flags" link (red arrow in image below). If I have any helpful flags, then the number of helpful flags should be displayed (blue arrow). If I have not flagged anything, then neither should be displayed (as with current site functionality).