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operating-systems interview questions

Top operating-systems frequently asked interview questions

How can I reinstall Windows 7 if I lost my installation DVD? [duplicate]

Possible Duplicate:
Where do I download Windows 7 (legally from Microsoft)?

I have lost my Windows 7 installation DVD, but I do have the license key. How can I get a Windows 7 DVD? Can I download an ISO image somewhere? While installing can I use my original Windows 7 Key?


Source: (StackOverflow)

Does every OS need RAM?

Is there an OS which can be used without RAM, specifically the kind I can create a bootable pendrive from and use it in the computer? This gets awkward, since booting is essentially loading OS in RAM.

Note: I originally wanted to know about a RAM-less OS to check if my laptop (which does not boot but presents a blank screen) RAM had gone bad, but I like the way this question has snowballed.


Source: (StackOverflow)

What does an operating system look like without a shell?

A shell like the bash or command.com (up to Windows ME) or CMD.EXE (in later versions) provides an interface that (among other things) accepts commands from the user. What does an operating system look like before a shell is run? How were systems used before the first shell was developed (e.g. UNIX in the early 1970s)? If a computer cannot even accept commands (there is no command line), how can a user interact with it? What is this most basic interface? Can I run this interface in a terminal emulator or is there no way going behind a shell?


Source: (StackOverflow)

How to make VIM settings computer-dependent in .vimrc?

I share my VIM configuration file between several computers. However, I want some settings to be specific for certain computers.

For example, font sizes on the high-res laptop should be different to the low-res desktop. And more importantly, I want gVIM on Windows to behave more windowsy and MacVim on OSX to behave more maccy and gVIM on Linux to just behave like it always does. (That might be a strange sentiment, but I am very used to switch mental modes when switching OSes)

Is there a way to make a few settings in the .vimrc machine- or OS-dependent?


Source: (StackOverflow)

What is the relationship between Unix, Linux, Ubuntu, Debian and Android?

What is the relationship between Unix, Linux, Ubuntu, and Debian?

I suspect they are all Operating Systems that are based upon one another - similar to how Windows is based on DOS. Is my suspicion correct? Do these operating systems have the same type of relationship with each other as Windows has with DOS? Are they related to DOS or Windows in any way?


Source: (StackOverflow)

How does the computer know that the PC was not properly shut down?

Actually, this question struck me because of power cuts in my house. When there is a power cut, there is a sudden loss of power from the computer.

How does the computer know that the shutdown was not properly done?


Source: (StackOverflow)

Overriding HOMEDRIVE and HOMEPATH as a Windows 7 user

My employer has an Active Directory group policy which sets my Windows 7 laptop HOMEDRIVE to "M:" (a mapped network drive) and my HOMEPATH to "\". Since I have read-only permissions for the root of that shared drive, I cannot create files or directories in my windows home directory. My attempts to work with the IT department have been unsuccessful.

Is there a way for me to globally change these envars at boot or login time? I need for all applications to use alternate values (such as "C:" and "\Users\myname"). I have some installed utilities (like gvim and others) that store preference files in the user's home directory.

IMPORTANT: Changing these envars under "System Properties > Environment Variables" does not work. I have tried setting these as both User and System Variables (including a reboot). TypingSET HOMEin a DOS window clearly shows that my settings are ignored. Also, using "Start in" in a Windows shortcut will also not solve this, as I need things like Explorer context menu items (like "Edit with Vim") to operate correctly.

I do have admin rights on this company laptop, but I am not a Win7 guru. Back in the day, a boot script would have solved this in a minute. Is it even possible today? Thanks.


Source: (StackOverflow)

How computers display raw, low-level text and graphics

My ever-growing interest in computers is making me ask deeper questions, that we don't seem to have to ask anymore. Our computers, at boot, as far as I understand it, are in text mode, in which a character can be displayed using the software interrupt 0x10 when AH=0x0e. We've all seen the famous booting font that always looks the same, regardless of what computer is booting.

So, how on earth do computers output graphics at the lowest level, say, below the OS? And also, surely graphics aren't outputted a pixel at a time using software interrupts, as that sounds very slow?

Is there a standard that defines basic outputting of vertices, polygons, fonts, etc. (below OpenGL for example, which OpenGL might use)? What makes me ask is why OS' can often be fine without official drivers installed; how do they do that?

Apologies if my assumptions are incorrect. I would be very grateful for elaboration on these topics!


Source: (StackOverflow)

Was Windows 95 an Operating System? [closed]

This question maybe a bit historical, but we didn't have Superuser at the time.

Around 2000 when I was starting my Computer science degree, a subject was Operating systems. The teacher asked us to list a few OS. I said Windows 95.

I was immediately shot down. Windows 95 wasn't on OS, as it used DOS to boot up. The actual OS was DOS, Win 95 was just a graphical wrapper around it.

I pointed that all trade magazines called Win95 an OS, but was told that they were run by laymen, and as a professional, I should know better. DOS was the only OS from Microsoft, at least till Win2K came out later that year.

So 12 years on, I'm still not sure. Could Win 95 be considered an OS?


Source: (StackOverflow)

Is Unix not a PC operating system? [closed]

I am doing my bachelor's degree at a university. In a written assignment, the professor posted the task: "Name three PC operating systems".

Well, I went on an included a variety of OSes (Linux, Windows, Mac OS X) and including Unix & Solaris. Today I received a mail from my professor saying:

Unix is not a PC operating system. Many Unix-variants are not PC-hardware compatible (like AIX & HP-UX. About Solaris: there was one PC-compatible version...)

I am kind of suprised: Even if many Unix-variants are PowerPC based and have a different bit-order – Those don't stop being PCs now, right?

The question was given in a written assignment! It was not a question that came up during the lecture!


Due to the original task being in German, I'll include it just to make sure nobody suspects an error in the translation.

Frage: Nennen Sie 3 PC-Betriebssysteme.
Antwort: Unix ist kein PC-Betriebssystem, viele Unix-Varianten sind nicht auf PC-Hardware lauffähig (AIX, HP-UX). Von Solaris gab es mal eine PC-Variante.


Source: (StackOverflow)

Before Operating systems, What concept was used to make them work? [closed]

The Operating systems have been tightly related to the computer architecture.An OS takes care for all input and output in a computer system. It manages users, processes, memory management, printing, telecommunication, networking etc.It sends data to a disk, the printer, the screen and other peripherals connected to the computer.

Prior to the introduction of Operating System,

What was used in computer systems to make them work?

Which concept was used to operating system in our evolution of computer?


Source: (StackOverflow)

Is it still necessary to shut down computers?

Nowadays with our modern operating systems, is it necessary to fully shutdown computers instead of choosing to stand-by or hibernate computers (desktops and laptops)?

Would there be any side-effects of keeping a computer running continuously without a shutdown (putting it to sleep or hibernating it when it is not used)? For example, hard drive life decrease, system internals (Processors, RAM etc.) aging faster than usual, etc?


Source: (StackOverflow)

Using UDF on a USB flash drive

After failing to copy a file bigger than 4G to my 8G USB flash drive, I formatted it as ext3. While this is working fine for me so far, it will cause problems if I want to use it to copy files to someone which does not use Linux.

I am thinking of formatting it as UDF instead, which I hope would allow it to be read (and possibly even written) on the three most popular operating systems (Windows, MacOS, and Linux), without having to install any extra drivers. However, from what I found on the web already, there seem to be several small gotchas related to which parameters are used to create the filesystem, which can reduce the compability (but most of the pages I found are about optical media, not USB flash drives).

I would like to know:

  • Which utility should I use to create the filesystem? (So far I have found mkudffs and genisoimage, and mkudffs seems the best option.)
  • Which parameters should I use with the chosen utility for maximum compability?
  • How compatible with the most common versions of these three operating systems UDF actually is?
  • Is using UDF actually the best idea? Is there another filesystem which would have better compatibility, with no problematic restrictions like the FAT32 4G file size limit, and without having to install special drivers in every single computer which touches it?

Source: (StackOverflow)

What technical reasons exist for not using space characters in file names?

Somebody I know expressed irritation today regarding those of us who tend not to use spaces in our filenames, e.g. NamingThingsLikeThis.txt -- despite most modern operating systems supporting spaces in filenames.

Are there technical reasons that it's still common to see file names without (appropriate) spaces? If so, what are these technical reasons that spaces in filenames are avoided or discouraged, and in what circumstances are they relevant?

The most obvious reason I could think of, and why I typically avoid it, are the extra quotes required on the command line when dealing with such files. Are there any other significant technical reasons?


Source: (StackOverflow)

32-bit vs. 64-bit systems

What are the differences between 32-bit and 64-bit systems?

If you have used both of them, what kind of sharp differences have you experienced?

Would it be a problem to use 32-bit programs on 64-bit systems in some cases?


Source: (StackOverflow)