Operating System Chapterwise Notes of Galvin:OS Structures

Pages>> 1 2 3 4 5 6 7 8

Here we are giving chapter wise notes of operating system based on operating system concepts by galvin

O.S STRUCTURES

q) what if 2 processes are associated with same program?
a) they are considered separate.

q) tell some impotant funcions of o.s?
a) process management,main memory management,file management,i/o system management, secondary storage management.

q) which protocol needs a clients to login before using server's resources and which does not need this?
a) that require log in are:- ftp,nfs(network file system).
do not require log in:- http

q) what is protection?
a) it is a mechanism for controlling access of programs,processes to resources defined by computer system.

q) what is command interpreter?
a) it is one of the most important system program of o.s, which is interface b/w user and o.s .some o.s include it in their kernel,others run it when job is initiated.

q) what is shell?
a) a program that reads and interprets control statements(commands given to o.s) is executed automatically.this program is called command line interpreter or shell.

q) tell some important o.s services?
a) it provides environment for execution of programs. some services are:-
1) program execution:-
2) i/o operations:- user can't control these operations, o.s need to carry out these.
3) file-system manipulation:-
4) communications:- it may be implemented by shared memory or message passing.
5) error detection:-
6) resource allocaton:-
7) accounting:- it may be used to bill users or by researchers to reconfigure the system.
8) protection:-

q) what are system calls?
a) these provide inteface b/w the process and o.s, and are generally available as assembly language instructions.

q) name some languages where u can make system calls directly?
a) c,c++,perl,assembly language.

q) give example of certain system calls?
a) display message on screen,open files, closing files, terminate normally or abnormally,read from or write to file,etc.

note:- we need to specify certain information that will be passed to o.s as parameter with system calls.

q) what are the various methods to pass parameters to o.s by system calls?
a) there are 3 methods:-
1) pass parameters in registers.
2) if parameters more then parameter stored in block in memory and address to block passed as parameter in register (linux use this).
3) some use stack.

q) what are different categories of system calls?
a) process control,file management,device management,information maintainance and communications.

q) in case of processes tell a common system call?
a) create process.

q) name some system calls dealing with the coordination of system processes?
a) wait time,wait event,signal event.

q) name for file system calls?
a) create,delete,read,write,reposition,get/set file attributes.

note:- device also behave as files only, system calls like request,release,read,write etc are there.

q) name some information maintainance system calls?
a) system call that return date and time,number of current users,version of o.s,about all processes etc.

q) system calls in case of communications?
a) get hostid,get processid. what these 2 return are passed as parameters to openconnection,close connection calls.then we have read message ,write message.

q) what are deamons?
a) most processes that will be recieving connections are special purpose deamons(system programs). they execute wait for connection call and gets awakened when connection is made.

q) what are system programs?
a) these are generally user interfaces to system calls.

q) how many types of system programs are there?
a) 1)file management:- these programs create ,delete,copy,rename,manipulate files and directories.
2)status information:- date,time,number of users,available memory etc.
3)file modification:-
4)programming language support:- compilers,assemblers,interpreters.
5)loaders,linkage editors.
6)help to browse web pages,send e-mails,send messages to other's screen,file transfer etc.

note:- most important system program for o.s is command interpreter.

q) in how many ways the commands can be implemented in o.s?
a) 2 ways:-
1)code for command is within the interpreter program.we can jump to that part , set parameters and make appropriate system call.
2)this is used by unix. command only tells name of file to be loaded and executed.parameter is passed to it.

note:- unix system consist of 2 parts:- kernel and system programs.

q) what is there in kernel?
a) kernel has device drivers, it provides file system,cpu scheduling,memory management and other functions through sytem calls.

Pages>> 1 2 3 4 5 6 7 8