for a help

Dear Sir:
   Sorry to bother you,whether you can read it or not ,first 
thank you. 
   I am a student of Peking University of P.R.CHINA.I am very 
interested in Linux recently because I want to see HOW  it's
kennel work and what is the difference between Minix(because
there is a book about how to reading the code,so it is easy to
understanding) and Linux,and I want to extract some main part 
of it such as process-managment,memory,filesystem and so on,so
I can make it a project to other students for os-class.
   And I have read parts of code of linux,I realize how it bootup
and how it arrange the real memory.But I still do not know how it
run up. I know how MINIX run and switch the process,but as I find
"kernel_thread" in main.c of linux,and then I do not know how it
make the thread into practice.Also I have some other questions,
because I find your email-address in code,so I think you are the
expert of linux,so If you can answer any of them ,please email me
thanks a lot. 
     or if you can tell me how to get to the answer ,that is also very
 kind of you.
  
  
  First of all:
    HOW DOES THE KENNEL RUN UP AND HOW DOES LINUX SWITCH THE PROCESS?
    USING IRET CLOCK_INTERUPT TO "_restart" as in MINIX ?
    OR THREAD OF LINUX ? 
    HOW DOES IT WORK?
    WHAT IS THE MEANING OF THE CODE OF kernel_thread() (in process.c)

****************************
  1: what is bde?(in bootsect.s)
  2: what is the big-kernel?(in setup.s)
  3: what is ramdisk?(in setup.s)
  4: why define some data at the end of the program,such as 
     "cmp setup_sig1,#SIG1" ( I mean "setup_sig1","#SIG1") ( in setup.S)
     what is the use of ".bss" ,".sect" which can be found at the end of 
     the file.
  5: how it define setup_sig1 or 2, how it is written?
  6: mov ax,#0xe801 int 0x15: what is it doing? 
  7: realmode_swtch is not a procedure,oh? but why some place call it?(in      setup.s)
  8: what is the use of a20?
  9: what is GPIO?( in /arch/i386/kernel/setup.c) 
****************************
10: what is "_end" in (/arch/i386/kernel/setup.c)
    there are "_end" ,"_text",something else,I think it sign the position of
    the kernel,but I can not prove it.
11: How is the init_task?
    I mean how it run up?
13: what is vmlinux.lds(/arch/i386/)
14: what does this line mean? (in /include/linux/sched.h)
    *t=(struct task_struct *)tarray_freelist;
    tarray_freelist=t;
    is it malocing the space?  

       

                            Thanks a lot.

                        

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