I felt difficulty in using the terminal. Can some one say the easier to learn this stuff,if you has experience with this. ex: If i want to modify a file and if i want to update some software etc.,   I want to know the commands for different things and what things we can do in terminal in ubuntu 14.04.
What is a terminal? How do I open a terminal window? How do I use the terminal?
When to use an interface instead of an abstract class and vice versa? Hide Accesibility icon from Panel I have Ubuntu 18.04 and set the Scaling Factor in Tweaks to 1,10 because the 1920x1080 resolution makes stuff on my screen look a bit too small for my taste. That toggled this stickman icon, which now seems to not want to go away from my Panel unless I disable "Large Text".    Is there any way to hide this icon while keeping my settings? How do I prove that a graph is a topological manifold I'm having problems with that:  Prove that M is a topological manifold.  $f:U \to \mathbb R^k$, U $\subset \mathbb R^{n}$ open, f continuous  M = $\{\left(x,y\right)\in \mathbb R^{n+k} \mid x \in U, y=f(x) \}$  Can anyone help me please? Sometimes I found that writing just "J. Doe" may lead, in a justified line with few words, to a big space between the initial and the surname. Using J.\,Doe looks ok but I would like to know if there is a general rule for spacing between initials and surnames. Is it possible for test error to be lower than training error Is it possible to have test error lower than training error?  I have a classification problem with 2000 samples, 500 of which are positives, 1500 are negatives. I split my data into 70% training data, 30% test data.  Run random forest with 200 estimators and cv=10. I did this several times and compared the recall and precision score and notice the scores for my test set is significantly better. Is this possible? Where can I find the location of downloaded .deb files?  I want to copy this folder before I reinstall Ubuntu so I don't have to redownload the packages.  I am running Ubuntu 12.10 32-bit.  How can I do this? Which folder is recycle bin in on Win7? How to check files there? I was using another account before. Let me call it account A. And I deleted a lot of files to the Recycle Bin at that time. But before I removed account A I forgot to empty the Recycle Bin.   My question is, are my files still there? I've searched and found that the Recycle Bin may live in $Recycle.Bin, but I can't open files there so I can't know what they are. Any help how to open deleted files or how to delete them permanently? Ubuntu boots from USB but get GRUB rescue after installation I can boot Ubuntu from USB, but when I took the USB stick out of the laptop and booted again, I got an error saying   Error: unknown filesystem. grub rescue&gt;   What can I do to fix this? Microscopic interpretation of pressure in liquids How do I contact other users? Let $F$ be a field. Why does $F[x]$ have infinitely many irreducible elements?   For the case F has characteristic 0  Then x-a is irreducible for all a $\in F$ since x satisfies no non-trivial relations in F.  Obviously this argument fails for a finite field since there are only finitely many a to choose from.  So how may I construct irreducible polynomials in a finite field?  I figure it must involve higher powers of x, maybe $x^n-a$ ? Do I need a bus/train/plane ticket out of Thailand in order to get a Visa-on-Arrival? Someone told me I need a ticket out of Thailand in order to enter.  I am traveling to Thailand, on March 18th. I have a Ticket from Bangkok to Sweden booked for June 4th.   I will be staying in Thailand for 2 weeks when I arrive there, then traveling around Cambodia, Laos and Vietnam until June 4th when I leave.   With that ticket out of Thailand, will I be able to get in and get a (30 day) Visa-On-Arrival (or not because the ticket out is not within the first 30 days). Or do I need to show proof that I am leaving within 2 weeks of being there at first? How do you remove a default program association for file types in Windows 7? I somehow have set the default file type association for a file type in Windows 7. It doesn't appear to be possible to delete it from the "Change the file type associated with a file extension" options screen. Is it possible to remove it? Book about space alien cats I read a book when I was young, it was about space alien cats. I believe the title was Quzzles, but I really don't know. The book was stolen from me before I was finished. I don't know much else about it. How fast a (relatively) small black hole will consume the Earth? This question appeared quite a time ago and was inspired, of course, by all the fuss around "LHC will destroy the Earth".   Consider a small black hole, that is somehow got inside the Earth. Under "small" I mean small enough to not to destroy Earth instantaneously, but large enough to not to evaporate due to the . I need this because I want the black hole to "consume" the Earth. I think reasonable values for the mass would be $10^{15} - 10^{20}$ kilograms.   Also let us suppose that the black hole is at rest relative to the Earth.  The question is: How can one estimate the speed at which the matter would be consumed by the black hole in this circumstances? Software recommendations Sci-fi book where humanity is rebuilt on a new planet after being wiped out Finding the variable name passed to a function How to concatenate items in a list to a single string? Flag dialogue popup is stacked behind realtime-post-deleted-notification banners There is a little bug that becomes visible when a page contains realtime-post-deleted-notification banners (that's the CSS classname of these red banners appearing on answers which just got deleted, see screenshot below) and you try to open the flag dialogue above them:    Obviously, the dialogue appears below the banners, which it clearly should not do. It also has no input focus, trying to interact with the dialogue fails and either closes it (clicking outside of the red banners) or reloads the page (clicking on the red banners).  The cause for this is simply the z-index ordering in the site's CSS. Relevant CSS snippets:  .realtime-post-deleted-notification {     position: absolute;     text-align: center;     z-index: 100; }  .popup {     display: none;     padding: 15px;     position: absolute;     z-index: 10; }   So the fix for this minor bug would probably be to raise the z-index of the popup class to something greater than 100.