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)

Other benefits of 64-bit OS apart from memory expansion?

I'm trying to convince somebody of the benefits of switching to a 64-bit OS but I'm having a hard time finding arguments other than "you can use more than 3GB RAM". Are there any other clearly-communicable benefits in having a 64-bit operating system?

Source: (StackOverflow)

65536 +1 Connection on a system

There are 65536 ports for every system in the network, and every connection or Send/Receive will use one of those.

My question is: what happens if we have 65536+1 connections?!

I know that it does not happens in normal way, but I'm curious to know how Operating Systems handle it.

Source: (StackOverflow)

How can I upgrade from Windows 7 to Windows 8 and keep my files and applications?

I want to upgrade from Windows 7 to Windows 8. How can I do this while keeping all of my files in-tact? Is it possible to retain all of my applications and user settings, too?

Source: (StackOverflow)

Why can't a 64 bit OS run a 16 bit application?

Why is it that:

  • a 32-bit OS, when installed on a 64-bit CPU, can run old 16-bit applications,
  • but if you install a 64-bit OS it can't run those applications directly and need some sort of emulation (that doesn't always work perfectly)?

To be more specific, I have an 64-bit processor (Intel Core 2 Duo). When I had Windows XP and Windows 7 (both 32-bit) installed, they could run old DOS and 616-bit Windows applications.

Now I have installed the 64-bit edition of Windows 7. Why can't it run those same applications anymore?

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)

cat /proc/meminfo what do all those numbers mean

In reading the man page on the free command in Linux. I found that is gets its info from /proc/meminfo.

I understand a few of the entries, like MemTotal and MemFree. What do the rest mean.

cat /proc/meminfo 
MemTotal:        3973736 kB
MemFree:          431064 kB
Buffers:           46604 kB
Cached:           494648 kB
SwapCached:        11360 kB
Active:          2322760 kB
Inactive:         933028 kB
Active(anon):    2057952 kB
Inactive(anon):   679956 kB
Active(file):     264808 kB
Inactive(file):   253072 kB
Unevictable:          16 kB
Mlocked:              16 kB
SwapTotal:       4096568 kB
SwapFree:        3961748 kB
Dirty:               236 kB
Writeback:             0 kB
AnonPages:       2704520 kB
Mapped:           182240 kB
Shmem:             23372 kB
Slab:              93848 kB
SReclaimable:      52044 kB
SUnreclaim:        41804 kB
KernelStack:        5064 kB
PageTables:        64928 kB
NFS_Unstable:          0 kB
Bounce:                0 kB
WritebackTmp:          0 kB
CommitLimit:     6083436 kB
Committed_AS:    7327800 kB
VmallocTotal:   34359738367 kB
VmallocUsed:      321156 kB
VmallocChunk:   34359411708 kB
HardwareCorrupted:     0 kB
AnonHugePages:         0 kB
HugePages_Total:       0
HugePages_Free:        0
HugePages_Rsvd:        0
HugePages_Surp:        0
Hugepagesize:       2048 kB
DirectMap4k:      225280 kB
DirectMap2M:     3895296 kB

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)

Why is "Everything is a file" unique to the Unix operating systems?

I often hear people say "Unix's unique philosophy is that it treats everything as a file" or "In Unix, everything is a file". But I've never heard anyone explain why it is unique to Unix.

So, why is this unique to Unix? Does other operating systems such as Windows and Macs not operate on files?

And, is it unique compared to other operating systems?

Source: (StackOverflow)

What's the difference between an Application, Process, and Services?

How are these fundamentally different "things" on Windows?

Aren't all running things Processes?

It seems that every Application has an associated process that shuts it down if it is shut down. One process can manage more than one application instance, it looks like. And Services, I'm not even sure what they are, exactly.

Are they not processes themselves?

Source: (StackOverflow)

What would happen if I take my hard drive out of my current PC and put it in a new PC?

Basically, I want to get a new PC, but I have so many software/games installed on my current hard drive, that I don't want to waste the time to re-install/re-configure. Would it work if I just take out my current hard drive, and stick it into a new PC? the motherboard/video card etc are all different, would the new PC boot up and work flawlessly?

The operating system is Windows 7.

Source: (StackOverflow)

What does an operating system look like without a shell?

A shell like the bash or (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)

Do 64bit software/applications require more RAM than their 32bit counterparts?

I just saw these minimum requirements for a game:

Memory: 2GB for 32-bit OS or 4GB for 64-bit OS

Why does the 64bit OS require more RAM than its 32bit counterpart?

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 is there in an Operating System other than the kernel

As I understand it, the kernel does all the interaction with the hardware, and manages the memory, the I/O devices, etc. So the kernel is doing everything, yet it is just a part of the operating system. So what else is there in an OS ? Just the applications that come bundled with it ? For example, what does Ubuntu have other than a kernel ? The Gnome Desktop, and a few other applications ?

Source: (StackOverflow)