Operating System Chapterwise Notes of Galvin:Intro

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


q) what is operating system?
a) manages the computer hardware..acts as intermediatery between user and hardware..provides environment for applications/ processes to work better.
---- resource allocator
---- control program

q) in how many parts a computer system can be divided?
a) four:-
1) hardware 2) o.s 3) application programs 4) users


q) early computer?
a) very large in size. were run only from console.user only used to give inputs manually.input devices were card readers and tape drives.output devices were line printers, tape drives and punch cards. batch programming was done. o.s of these batched system had only 1 task to do: transfer control automatically from 1 job to another.

q) What is job pool?
a) it is collection of jobs on disk,ready to come to main memory.

note:- job scheduling and cpu scheduling are different

q) when do o.s first thought for users means processes?
a) when concept of mutiprogramming came.

q) what is time sharing or multitasking systems?
a) here cpu executes multiple jobs by switching between them, and that also so fast that users interact with program when it is running.

q) how do we achieve time sharing concept?
a) using cpu scheduling and multiprogramming.

q) give example of desktop systems?
a) pc's running under windows and apple machintosh.

q) what is multiprocessor system?
a) also called parallel system and tightly coupled system.more than 1 processor in close communication with same clock,and bus or may be memory and i/o devices.

q) what is meant by graceful degradation?
a) suppose we have 10 processors. 1 fails then other 9 can share work of failed 1.thus system runs only 10% slower than totally failing.this ability to continue providing service propotional to level of surviving hardware is called graceful degradation. systems are called fault tolerant.

q) what is tandem system?
a) uses duplication of hardware and software both. 2 identical processors with own memory and connected by bus. 1 act as primary and other as backup.checkpoints are used to give information to backup processor.

q) explain smp?
a) symmetric multiprocessing. here each processor runs copy of o.s and communicate with each other as required.

q) define asmp?
a) asymmteric (here we have master slave relationship b/w processors)

q) give an example of smp?
a) Encore's verion of unix.

q) what issues in multiprocessing?
a) * i/o (data must reach appropriate processor)
* 1 is idle and other is overloaded.

q) what is distibuted system?
a) take use of networking. processors at different places and use different clocks and donot share memory also.

q) name protocols supported by windows and unix?
a) tcp/ip.

q) types of server systems?
a) 1) compute servers 2) File servers

q) what is distributed lock manager service?
a) clusters donot allow shared access to data on disk. for this distributed file system provide access control and locking to files to avoid conflicts.

q) what are real time systems?
a) here rigid time requirement is placed on the operation of processor or data flow. processing must be done in defined time constraint.

q) give area of application of real time systems?
a) medical imaging,scientific experiments,weapon systems,home appliance controller etc.

q) types of real time systems?
a) hard and soft.

q) features of hard?
a) * critical tasks done. * limited or no secondary memory , only ROM. *no virtual memory * no time sharing concept. * o.s is very simple

q) what are handheld systems?
a) include pda ie personal digital assistants. eg cellular phones.

q) limitations of handheld systems?
a) small memory, small display and slow processor due to small battery.

q) under what category do pc's come?
a) microcomputers.

note: clusters share a storage.




Exercise:-


q1) three main purpose of o.s?
a) 1) resouce allocator 2) control program 3) manage hardware 4) file system

q2)difference b/w operating system for mainframes and pc's?
a) pc's os were mainly concerned with convenience and responsiveness rather than cpu and device utilization.they lacked multiuser and multitasking.file protection ,new feature of operating system.

q) what are security problem related to multiprogramminG and multitasking environment?
a) more than 1 program in memory , so need mamory management and protection.need to take care of cpu scheduling,job synchronisation, and also take care of deadlock prevention.

q) some properties:-
a) type of operating system features

1) batch very big, run from console,input on tapes,card readers,o.s only used to transfer control from 1 job to next.

2)interactive direct communication b/w user and o.s or program.

3)time sharing executes multiple jobs by switching b/w them,user can interact with jobs.uses cpu scheduling and multiprogramming.virtual memory came.
disk management(as file system), take care of job synchronization and communication, memory management.

4)real time rigid time requirements are placed on the processor or flow of data.can be hard or soft.

5)parallel more than 1 processor with same clock and share same memory.concept of graceful degradation. can be smp or asmp

6)Distributed depend on network.mutiple processors but at distant places. they donot share same memory and clock.

7)clustered 2 or more individual systems coupled together.linked through lan and share storage. can be asymmetric or symmetric clustering.also we have
parallel clusteing. they have facility called dlm(distributed lock manager).

8)handheld small memory, slow processor,not having virtual memory concept,

note:- o.s waste resources in case of PC's where user convenience and responsiveness is major aim to achieve.

q) what is being used in multiprocessing along with main CPU?
a) microprocessors with its own memory.

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