OPERATING SYSTEM
CHAPTER – 1 NOTES
1. INTRODUCTION
Software:-
·
Program is a collection of code/instruction.
·
Software is a collection of program.
Hardware:-
·
Physical device is a collection of computer
system is called Hardware.
For example:-processor, RAM,HD,I/O devices.
Types of Software:
Software is divide into three types:
1.
System software:-
The software which is used to perform
all types of system level work of the computer system is called system
software.
Example of system
software:-
1)
Operating
system:-
Operating system provide on interface
between user and computer system.
e.g.:- UNIX,
LINUX, MS-DOS, Windows XP, Windows 2000, Windows NT.
2)
Compiler:-
Compiler is used to convert high level
language into machine level language.
3)
Interpreter:-
Interpreter is used for converting high
level language into machine level language line by line.
While
compiler convert whole program at a time.
4)
Linker:-
Linker is used to link the programs.
5)
Loader:-
Loader is used to load
the program.
6)
Assembler:-
Assembler is used to
convert Assembly language into machine level.
2. Utility Software :-
The software, which provide an additional meaning
to the computer system.
e.g.:- calculator,
MS-paint….
3. Application Software:-
The software which is
created by users, using the different high level language and database system
for any special purpose.
For ex.:- Library
management system software for manage the library works.
- Banking software for
manage the Bank works.
Computer system
is divide into four components:
1. Hardware
2. Operating
system
3. Application
pro.
4. User.
à Users are use computer system to solve the
different problem, so there may be many application programs and system
programs to solve the problems of users.
à The operating system control and co-ordinates
the use of the hardware among the various application program for the different
user.
à Operating system provide an interface between the user’s
application program and hardware of
computer system.
à Operating system provide an environment to
users to use the computer system.
à The
components of computer system are hardware, software, and data the operating
system provides the means to use these components in the operating of computer
system.
à
Operating system makes the use of system easier.
Justify that operating system is like a Government………………
operating
system provide an environment to use the computer system.
Government also
provides facilities to the peoples like providing job opportunities, making new
plans for facilities of peoples, solve problems of peoples.
So, operating system
is similar to government.
à Operating system provide services like
process management, memory management, file management, resource allocation and
protection to the system..
à Operating system act as a resource allocation:
In computer
system many resources are require to solve the problems of users & computer
system, resources are : CPU, memory, i/o devices, file storage etc…
à All these resources allocate to
specific programs and users as per the requirement to perform specific tasks by
the operating system.
à Operating system allocate the
resources, according to the request are come, to operate the computer system
efficiently.
e.g.:- UNIX, DOS, Windows XP, etc
SERVICES OF
OPERATING SYSTEM:
Types of
Services are following:
1.
PROGRAM EXECUTION:-
The system
must be able o load a program into memory and run it. The program must be able
to complete its execution either normally or abnormally with indicating the
errors.
2.
I/O OPERATION:-
System
running program may require I/O. This I/O involves a file or an I/O device. The
operating system provide mean to do. Also it manages all I/O operation.
3.
FILE SYSTEM MANIPULATION:-
Operating system maintains the file system
file system do and manages all types of operation doing on the file like:
creating, writing, reading, appending, truncating.
4.
COMMUNICATION:-
Some time process need to exchange the
information with another process.
if both process are on same computer than
communication will be done by shared memory. If both processes are on different
computer in a network, then message passing technique is used. Message is a
packet of information.
5.
ERROR DETECTION:-
The operating system constantly needs to be
aware of possible errors. Errors may come in CPU, in memory or in any hardware
or any I/O devices. And also error may come in user programs.
For each type of error operating system should
take appropriate action. Operating system will detect the errors and give to
the users. Operating system will not solve or remove any error.
6.
RESOURCE ALLOCATION:-
Operating
system manage all resources of computer system like CPU cycles memory and file
storage. These resources are allocated to the multiple users as per the
requirement of users.
7.
ACCOUNTING :-
Operating system will keep record of which
users use how much and what kind of resources.
8.
PROTECTION :-
Operating system provide security mechanism to
protect the system from access of unauthorized users. By given the username and
password to the system.
Program And Process:
Program: Program is set of code or
instruction.
Process:- when program is going for the execution
it is called process.
Programs
are resided in secondary memory and Process are reside in Main Memory.
Program is Passive entity.
Process is active entity.
- Shell :-
Commands are given to the operating system by control statement, a program
which read and interpret this control statements is called Shell.
à function
of shell is get the next command statement and execute it”.
- System call:- A
system call is a request made by any program to the operating system for
performing tasks.
-System calls provide the interface between a process and the
operating system.
3. Kernel:-
Kernal is main program of operating system which load first in main memory. And
run all time into the computer system.
à Kernel is
heart of operating system. Kernel provide the services of operating system like
CPU management , memory management, file management through the system call.
Types of Operating System :
1.Single User-Single task
One User
can effectively do one thing at a time.
Example:
Palm Computer.
2. Batch Operating System:-
Operating system always resident in memory.
à In this type of operating system prepare the job consists of data, program,
and control information about the job and submit it to the computer.
à Here, operating system will transfer
control from one job to next.
·
In Batch operating system, jobs will batched
together and run through the computer as a group.
·
This batching of jobs will increase the speed of
processing.
·
Batch operating system will read the stream of
separate jobs, when job is complete, its output is printed.
·
Here job is prepared and submitted and after
some time output appears.
·
Turn around time:- The time
between job submission and job completion is called turn around time.
·
In Batch OS, no interaction between user &
job, when job is executing.
·
In Batch O.S. is often Idle.
* SPOOLING:- (simultaneous peripheral
operation online)
- Every job will be submitted into the
pool which will store the jobs,
- Job will be executed one by one by the
CPU, and after the execution of the job the output will be printed on
the output.
- Buffer will store the job incoming from
the input side, and also it will contain the job after its completion
of job, until the output is not ready for the print the output.
- This process is called spooling.
- Provide
less processing speed.
3. Multiprogramming
operating system:
·
This O.S. is different from Batch O.S.
·
In Multi programming O.S., multiple jobs are
keep in main memory .
·
Here, CPU will execute only one job at a time from
the multiple jobs.
·
All job is store in job pool, job will be
execute by CPU one by one.
·
Here job will come for execution from buffer in
the FIFO (First in First out) manner.
·
The job which come first into the buffer, it
will execute first.
·
When one job is executing, other jobs have to
wait, when execution will complete, another job will execute from the buffer.
·
When job selecting from the buffer it will load
into main memory, it is called JOB
SCHEDULING.
·
User can execute more than one program
simultaneously.
·
Here CPU is never idle. CPU can busy more of the
time.
·
Here the multiple programs and only one CPU for
execution of these multiple programs.
·
Multiprogramming is also called multitasking os.
·
This type
of OS are provides better resource utilization.
4. Multiprocessing Operating System.:
·
When more than program or task executes same
time it is called multiprocessing.
·
Multiprocessing use more than one processor.
·
In multiprocessing O.S. multiple processes are
executed by multiple processor at a time.
·
Here the CPU
scheduling is required every time,
O.S. will schedule the CPU. One CPU will execute one program at a time.
·
Provide
good processing speed: more than one task execute at a time.
·
Provide reliability:If any processor failure
,system will not fail.
·
In Multiprogramming
----- Job scheduling.
§ Multiprocessing ------ CPU scheduling.
5. Multitasking Operating system:
In multitasking, only one CPU
is involved, but it switches from one
program to another so quickly that it gives the appearance of executing all of
the programs at the same time.
6. Multithreading Operating System:
à In this type of O.S. the process will be
devide into the threads.
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1
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2
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3
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4
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5
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6
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7
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Thread
·
Here the process is divide into 7 threads.
·
Thread will execute instead of whole process.
Thread is called light weight process (LWP), while the process is heavy weight
process(HWP).
·
Definitionà Thread is called execution stream of process.
·
Here the execution of thread will done according
to thread ID. Multiple thread will execute by same time of different processes.
à There
are two types of Thread:
1).
User Threads:
Here
the thread creation and thread execution will be done at the user level. Here
the management of thread will done by users, kernel is unaware from these
threads. Thread creation and scheduling is done in the user space.
2) Kernal Threads:
Kernal threads
are supported by the O.S., here thread creation scheduling management is done
by kernel in kernel space. Kernel threads slower to create and manage while
user threads are faster.
è Advantage
Of multithreading O.S.
1. Responsiveness:-
Threads
performing lengthy operation and increasing responsiveness to the user.
2. Resource sharing:-
Thread
are share resources of process and memory.
3. Economy:-
Threads
economical to create compare to process.
4. Utilization of multiprocessor
architecture:-
Each
thread may be running parallel on a multiprocessor system.
=> Tightly
coupled System :
Systems have more than one processor in
close communication sharing the computer bus, clocks, memory and peripheral devices
this type of system is called Tightly coupled system.
=> Loosely
coupled System ;
System in which instead of memory and CPU clocks, system will share
every resource and base of computer system.
7.Network Operating System: (NOS)
- NOS share the activities of multiple
computer across the network.
- NOS work as director for sharing this
network. NOS is type of tightly coupled system.
There are two types of NOS
- Peer to Peer
- Client / Server.
- Peer
to Peer n/w:
à In Peer to Peer NOS, user can share resources
and files between the computer connected into network.
à Here 4 computers are connected directly with
each other to share the files are resource of other computer connected into the
network.
à Advantage: * less expense – no need of dedicated
server.
* setup is very easy.
à Disadvantage. : * No one
central connection.
* Does not provide good security.
2.Client
/ Server :
à Here every computer into the network, directly
connected to the server. Computer are not connected each other like Peer to
peer n/w.
à Here, one
server and 3 computer are connected to server is called client.
à server :
The computer which provide the service.
à Client :
The computer which accept the service or use the service provided by server.
à All types
of resources are available from server. Client send request to server for use
any resources or file and server will provide these resources or file requested
by client.
à Novell
network and windows NT server are example of Client/server NOS.
Advantage:
* Resources & data security
controlled by server.
*Any new client easily add or replace.
*New technology can be easily integrated
into system.
*All components work together.
*Server can access any client.
à Disadvantage:
* Heavy expense for create the server.
* Not easy to maintain.
* If server goes down then system will
not work properly.
·
Here Processors can share every resource like
CPU clock, memory cycles.
·
In PC have operating system.and users aware from
the all users in network.
·
NOS has also single processor, but it need NIC
care and some network related functionalities in PC ,for example TELNET,FTP
etc.
·
Example: Windows NT, Novell Netware.
8. Distributed Operating System (DOS)
·
In DOS Multiple computer are connected into
close communication to share the files and resources.
·
DOS is the LOOSELY COUPLED SYSTEM. Rather than
CPU clock and Memory everything can share between computers.
·
DOS provides system wide sharing of resources
files and I/O devices. DOS provide facility to access remote resources,
communication with remote process.
·
Main aim of DOS is to balance the load of
processors. OS automatically distributes the load on ther machine if any processor
have higher load.
·
User don’t know where his programming is
executing.
·
In Distributed O.S. each processor has its own
local memory and CPU clock.
·
In DOS every users are not aware from other users means
transparency achieved in DOS.
à Following
are the characteristics of DOS:
1.
Resource sharing
2.
computation speedup
3.
Reliability
4.
communication.
9.Real time Operating System:
à Real time operating system are used where rigid
time requirement on operation of processor.
à A real time O.S. has well defined fixed time
constraints. Here the processing must be done within the defined constraints or
the system will fail.
à Real time work properly and give correct result
if work is finish within time constraints
Air traffic control systems are example
of such OS.
Two types of real time O.S:
1.
Hard real time System:- guarantees that critical
task complete on time.
2.
soft real time System:- work according to
priority of task.
soft
real time o.s. has limited utility than hard real time system.
QUESTIONS
- Define O.S. .Explain Concept of OS.
- Explain various System Software.
- Compare Multiprogramming and Multiprocessing
O.S.
- Discuss Distributed OS and Network OS.
- Explain types of services provided
by O.S.
- Explain Real-time OS.
- Explain Multithreading OS
- Explain batch Operating system.
- What is shell, kernel, system call?
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