lecture number 2

Question 1

OS play role as resource manager
what is resource manager?

Answer 1

resource manager can be define as a component of OS which keep track of avalable software or HW for a system or project.

Question 2

cpu?

Answer 2

the processor that perfome multiple computation

Question 3

main memory

Answer 3

it stores all data which is used by cpu it is near to cpu

Question 4

sytem bus

Answer 4

cumminacation between I/O,memory ,cpu and HW

Question 5

cpu perform basisc three operation name and define

Answer 5

they are
1)fatch: retrive data from main memory address whos value is in PC
2)decode: decode or intrupt the fatched instruction
3)exction: excute it

Question 6

mechine language

Answer 6

set of instruction by which cpu can talk with HW directly
it is set of binary number
instruction is sequance of bits
smallest bit is 1 bit i.e 1 or 0
word is 32 to 63 bit

Question 7

instruction set of mechine languge

Answer 7

instruction of mechone languge
two parts
oprand = cpu register or main memory address
operator = opcode

Question 8

cpu register define and two type

Answer 8

small chip reghister size is one cpu word
genral purpose reggister are : eax,ebx
speacial purpose : esp(stack piotern),ebp(base pionter),eip

Question 9

mian memory desing and working

Answer 9

consist of cels each cel is made of 8 bit i.e 1 byte or multiple of it i/e 32 bit which is 4 byte
I/O and cpu refer cell address to read and write from main mem

Question 10

system bus define and part

Answer 10

one bus control every thing
3 parts
1)data bus : carry infromation
2)address bus : decide where to put
3) control bus : which operation to use

Question 11

I/O device parts and device controler define

Answer 11

two parts
1)device itself
2)divece controller: chip or chips that control physical deivece i.e part1

Question 12

how OS or cpu write or read from I/O

Answer 12

they read by device controll driver which help to connect device controller and OS
deivce controller have different registers
1)status reg: tell to cpu the current status of IO
2)constroll reg : used by cpu to control IO
3)data reg : read data or write to IO

Question 13

Por t- vs. Memor y-Mapped I/O

Answer 13

port mapped : acccess controll register using different io address space
mapped io : access controll register using same main memory address space

Question 14

performing i/o task steps

Answer 14

polling : cpu check for status
itrupet driven : cpu get intruptfrom deice controller either it is succefull or not
programmed io : cpu works on io data
DMA : direct memory acces : here the data is attached and retrive from io deivece directly to cpu

Question 15

privelged instruction and who can excute it

Answer 15

those instrunction which are harmful or sensitive and must be kept away from users
e.g is HLT : which stop or halt the system
INT X: which intrupt operation x
it can be exuted onlly by OS i.e in kernal mode

Question 16

two user mood in cpu instruction and thier def are ?

Answer 16

kernal mode : it is unrestrid mode it has done by OS and in then mode os can do anything
user mode @ it is restricted here we can not do follwing thing
we can not access address of io
we can not perform senstive instruction like HLT etc
we can not change the content of main memory
can not swtich to kernal mode

Question 17

how cpu knwo we are in which mode

Answer 17

it given by HW and it has one bit i.e 0 = kernal and 1 = user

Question 18

how HW give mem protection ?

Answer 18

by two registers
base register @ it give the intial address
limit reg @ it give the final limit address register
so once the user porg start the os takes these two regster
and our cpu check for theese two reg refrence once the refernce is reached to limit reg so the job is finsh that is prog is end

Question 19

exception and interupt diff

Answer 19

exception is SW gernted like deived by zero
intrupt is HW genrated

Question 20

TRAP @ meaning, usage types

Answer 20

when we change from user to OS kernal mood so called TRAP
done by three ways
1) system calls : when the prog is runnung and we want to wite in a file in dicks so kernal moode on
2) exception call : in user mood when exceotion accour so kernal mood call to handle it
3) in user mood when intrupt accour by HW so again kernal needed to handle

Question 21

user interface (user prog os interface)

Answer 21

it is between user prog and os but above the system calls it gve us follwing work
os procedure to excute senstive innstruction
it is written in highly level lag
it can be acces by high level langue application prog interface API rather than system calls

Question 22

5 main catog of sys call ?

Answer 22

1) process controll
2) file manag
3) divce manag
4) info mantaince
5)communaction

Question 23

process controll in sys call

Answer 23

it has end, abor t, load, execute, c r e a t e process, t e r m i n a t e process etc
when one stope so other must starts

Question 24

file managment in sys call

Answer 24

in has create file, delete file, open, close, read, write etc
supported on directries and ordinary files

Question 25

deivice manag in sys call

Answer 25

Include request device, r e l e a s e device, read, write, reposition etc

Question 26

information maintaince in sys call

Answer 26

Include calls to get/set the time, date, system data, and process, fi l e , o r
device attributes

Question 27

communaction in sys call

Answer 27

Include create/delete communication connection, send/receive messages,

Question 28

communaction have two phase
1) massage pass
2) shared mem
discuse both breifly

Answer 28

1) messgae passing:
here the communatioction must gove support to sys call to idetify a process with whom we message
wait for incoming message
establish a connection bet two process
2) shared mem must give support to call
to access or creat mem that will be shared by process including threads
provide lock
provide shared mem or free up it

Question 29

three methods to pass paramters in os is ?

Answer 29

1) put paramter inside the register but we may have more para than availble reg
2) put para in mem so the address of mem works as param
3) push into stak and popped up by os