I am reading the book REd hat 7 unleashed and the note on the 841 pages says me that all distros have modified the original linux kernel accordings to them so if we modify the kernel and copile, we might not get some features working (which featuress? and why ?)

is there any way that i modify linux kernel and then i can use it as a separate os?

refer to linux kernel in a nutshell-
http://www.kroah.com/lkn/

thank you but suppose i've just downloaded the latest Linux kernel and i want it to work as my os in virtual box right now .. how to do this.. no matter if it is just command line.

You'd have to install an operating system in virtualbox and then compile it in it.

thank you. but i am a real newbie with just 2.5 years of experience in Linux. Can you tell me the next all steps in brief, please ?

@cola :
thanks a lot but I can't resolve the following error :

root@aarsh-desktop:/usr/src/linux-2.6.34# make menuconfig
HOSTCC scripts/basic/fixdep
HOSTCC scripts/basic/docproc
HOSTCC scripts/basic/hash
HOSTCC scripts/kconfig/conf.o
scripts/kconfig/conf.c: In function ‘conf_askvalue’:
scripts/kconfig/conf.c:105: warning: ignoring return value of ‘fgets’, declared with attribute warn_unused_result
scripts/kconfig/conf.c: In function ‘conf_choice’:
scripts/kconfig/conf.c:307: warning: ignoring return value of ‘fgets’, declared with attribute warn_unused_result
HOSTCC scripts/kconfig/kxgettext.o
*** Unable to find the ncurses libraries or the
*** required header files.
*** 'make menuconfig' requires the ncurses libraries.
***
*** Install ncurses (ncurses-devel) and try again.
***
make[1]: *** [scripts/kconfig/dochecklxdialog] Error 1
make: *** [menuconfig] Error 2

You posted your own answer:

it worked. thanks all.

All is going now smooth. I am about to replace the kernel.
But, I 've to press y/n/m for about 200-250 choices it asking me on the command prompt. can I avoid it or speed it up , If I want to keep just defaults ???

You can use the old config as the basis. Just copy the existing /boot/config** from the kernel you are running now and paste it into the kernel directory (where you are building it) as .config

Then you can run make oldconfig
It might ask you a few questions if the kernel sources are newer that your .config

How do I access the Linux code to customize for my destinct application?

Hi and welcome to LQ.

You shouldn't hijack someone else's thread. Create your own one with your query (and please be more specific because I have no idea what you mean).

@chucks924 :

First of all, welcome to LQ.
Generally you will get the source code of slackware Linux is located at /usr/src/Linux-2.6.xx location.

I have tried to upgrade my linux kernel it also asked me for configurations like that for HDD, IPC , n/w and all that 100s of by selecting b/w Y / N / M. but now there are two problems ;

1. main problem is, still uname -a gives me the older version no.
2 My mouse has stopped working. But key board works well.