Basics of Operating Systems Definition – Generations of Operating systems – Types of Operating Systems, OS Service, System Calls, OS structure: Layered, Monolithic, Microkernel Operating Systems – Concept of Virtual Machine

1. Introduction of Operating
System
Usha Barad
Assistant Professor

2. 2140702-
OPERATING SYSTEM

3. SYLLABUS
1 Introduction:- Basics of Operating Systems Definition – Generations of
Operating systems – Types of Operating Systems, OS Service, System Calls,
OS structure: Layered, Monolithic, Microkernel Operating Systems – Concept of
Virtual Machine
2 Process Management :- Processes: Definition , Process Relationship ,
Process states , Process State transitions , Process Control Block ,Context
switching – Threads – Concept of multithreads , Benefits of threads – Types of
threads
• Process Scheduling: Definition , Scheduling objectives ,Types of
Schedulers ,Scheduling criteria : CPU utilization, Throughput, Turnaround Time,
Waiting Time, Response Time (Definition only) , Scheduling algorithms : Pre
emptive and Non , pre emptive , FCFS – SJF – RR , Multiprocessor scheduling :
Types , Performance evaluation of the scheduling.
3 Interprocess Communication :- Race Conditions, Critical Section, Mutual
Exclusion, Hardware Solution, Strict Alternation , Peterson’s Solution, The
Producer Consumer Problem, Semaphores, Event Counters, Monitors,
Message Passing, Classical IPC Problems: Reader’s & Writer Problem, Dinning
Philosopher Problem etc., Scheduling , Scheduling Algorithms.

4. 4 Deadlocks:- Definition,Deadlock characteristics , Deadlock Prevention ,
Deadlock Avoidance :banker’s algorithm, Deadlock detection and Recovery.
5 Memory Management :- Basic Memory Management: Definition ,Logical
and Physical address map , Memory allocation : Contiguous Memory allocation
– Fixed and variable partition – Internal and External fragmentation and
Compaction , Paging : Principle of operation – Page allocation – Hardware
support for paging –,Protection and sharing – Disadvantages of paging.
• Virtual Memory: Basics of Virtual Memory – Hardware and control structures –
Locality of reference, Page fault , Working Set , Dirty page/Dirty bit – Demand
paging ( Concepts only) – Page Replacement policies : Optimal (OPT) , First in
First Out (FIFO), Second Chance (SC), Not recently used (NRU) and Least
Recently used (LRU)
6 I/O Management :- Principles of I/O Hardware: I/O devices, Device
controllers , Direct memory access Principles of I/O Software: Goals of Interrupt
handlers , Device drivers , Device independent I/O software , Secondary-
Storage Structure: Disk structure ,Disk scheduling algorithm

5. 7 File Management :- File concept, Aaccess methods, File types, File operation,
Directory structure, File System structure, Allocation methods
(contiguous,linked, indexed), Free-space management (bit vector, linked list,
grouping), directory implementation (linear list, hash table),efficiency &
performance.
8 Security & Protection :- Security Environment, Design Principles Of Security,
User Authentication, Protection Mechanism : Protection Domain, Access
Control List
9 Unix/Linux Operating System :- Development Of Unix/Linux, Role &
Function Of Kernel, System Calls, Elementary Linux command & Shell
Programming, Directory Structure, System Administration Case study: Linux,
Windows Operating System

6. BOOKS
• Reference Books:
1. Operating System Concepts (8th Edition) by Silberschatz, Peter B.
Galvin and Greg Gagne, Wiley-Indian Edition (2010).
2. Modern Operating Systems (Third Edition) by Andrew S Tanenbaum,
Prentice Hall India (2008).
3. Principles of Operating Systems by Naresh chauhan, Oxford Press
(2014).
4. Operating Systems by D.M. Dhamdhere, Tata McGraw Hill 2nd edition.
5. Operating Systems (5th Ed) – Internals and Design Principles by
William Stallings, Prentice Hall India, 2000
6. UNIX Concepts and Applications(4th Edition)– by Sumitabha Das, Tata
McGraw Hill.
7. Unix Shell Programming – by Yashwant Kanetkar, BPB publications.

7. OPERATING SYSTEM

9. CONTINUE…
• An Operating System (OS) is system software that manages
computer hardware and software resources and provides
common services for computer programs.
• The operating system is the most important program that runs
on a computer.
• Every general-purpose computer must have an operating
system to run other programs and applications.
• Operating systems perform basic tasks, such as
recognizing input from the keyboard, sending output to
the display screen, keeping track of files and directories on
the disk, and controlling peripheral devices such as disk
drives and printers.

10. CONTINUE…
• Definition:
 An operating system is a program that acts as an
interface between the user and the computer hardware
and controls the execution of all kinds of programs.

11. • Following are some of important
functions of an operating System.
– Memory Management
– Processor Management
– Device Management
– File Management
– Security
– Control over system performance
– Job accounting
– Error detecting aids
– Coordination between other software and
users

12. • Memory Management:
– Memory management refers to management of Primary Memory or
Main Memory. Main memory is a large array of words or bytes
where each word or byte has its own address.
• Processor Management:
– In multiprogramming environment, OS decides which process gets
the processor when and how much time. This function is called
process scheduling. Operating System does the following activities
for processor management.
• Device Management:
– OS manages device communication via their respective drivers.
Operating System does the following activities for device
management.
• File Management:
– A file system is normally organized into directories for easy
navigation and usage. These directories may contain files and
other directions. Operating System does the following activities for
file management.

13. • Other Important Activities:
• Security -- By means of password and similar other
techniques, preventing unauthorized access to programs
and data.
• Control over system performance -- Recording delays
between request for a service and response from the
system.
• Job accounting -- Keeping track of time and resources
used by various jobs and users.
• Error detecting aids -- Production of dumps, traces, error
messages and other debugging and error detecting aids.
• Coordination between other softwares and users --
Coordination and assignment of compilers, interpreters,
assemblers and other software to the various users of the
computer systems.

14. Generations of Operating
System
• Early Evolution:
– 1945: ENIAC, Moore School of Engineering,
University of Pennsylvania.
– 1949: EDSAC and EDVAC
– 1949 BINAC – a successor to the ENIAC
– 1951: UNIVAC by Remington
– 1952: IBM 701
– 1956: The interrupt
– 1954–1957: FORTRAN was developed

15. • Operating Systems by the late 1950s
• By the late 1950s Operating systems were well
improved and started supporting following
usages:
– It was able to Single stream batch processing
– It could use Common, standardized, input/output
routines for device access
– Program transition capabilities to reduce the overhead
of starting a new job was added
– Error recovery to clean up after a job terminated
abnormally was added.
– Job control languages that allowed users to specify the
job definition and resource requirements were made
possible.

16. • Operating Systems In 1960s:
– 1961: The dawn of minicomputers
– 1962 Compatible Time-Sharing System (CTSS) from
MIT
– 1963 Burroughs Master Control Program (MCP) for the
B5000 system
– 1964: IBM System/360
– 1960s: Disks become mainstream
– 1966: Minicomputers get cheaper, more powerful, and
really useful
– 1967–1968: The mouse
– 1964 and onward: Multics
– 1969: The UNIX Time-Sharing System from Bell
Telephone Laboratories

17. • Supported OS Features by 1970s:
• Multi User and Multi tasking was
introduced.
• Dynamic address translation hardware and
Virtual machines came into picture.
• Modular architectures came into existence.
• Personal, interactive systems came into
existence.

18. • Accomplishments after 1970:
– 1971: Intel announces the microprocessor
– 1972: IBM comes out with VM: the Virtual Machine Operating
System
– 1973: UNIX 4th Edition is published
– 1973: Ethernet
– 1974 The Personal Computer Age begins
– 1974: Gates and Allen wrote BASIC for the Altair
– 1976: Apple II
– August 12, 1981: IBM introduces the IBM PC
– 1983 Microsoft begins work on MS-Windows
– 1984 Apple Macintosh comes out
– 1990 Microsoft Windows 3.0 comes out
– 1991 GNU/Linux
– 1992 The first Windows virus comes out
– 1993 Windows NT
– 2007: iOS
– 2008: Android OS

19. Types of Operating System
• Following are some of the most widely
used types of Operating system.
–Simple Batch System
–Multiprogramming Batch System
–Multiprocessor System
–Distributed Operating System
–Real-time Operating System

20. SIMPLE BATCH SYSTEMS
• In this type of system, there is no direct interaction between
user and the computer.
• The user has to submit a job (written on cards or tape) to a
computer operator.
• Then computer operator places a batch of several jobs on
an input device.
• Jobs are batched together by type of languages and
requirement.
• Then a special program, the monitor, manages the
execution of each program in the batch.
• The monitor is always in the main memory and available for
execution.
• Following are some disadvantages of this type of system :
– Zero interaction between user and computer.
– No mechanism to prioritize processes.

21. MULTIPROGRAMMING BATCH
SYSTEMS
• In this the operating system, picks and begins to execute one job from
memory.
• Once this job needs an I/O operation operating system switches to
another job (CPU and OS always busy).
• Jobs in the memory are always less than the number of jobs on
disk(Job Pool).
• If several jobs are ready to run at the same time, then system chooses
which one to run (CPU Scheduling).
• In Non-multiprogrammed system, there are moments when CPU sits
idle and does not do any work.
• In Multiprogramming system, CPU will never be idle and keeps on
processing.
• Time-Sharing Systems are very similar to Multiprogramming batch
systems. In fact time sharing systems are an extension of
multiprogramming systems.
• In time sharing systems the prime focus is on minimizing the response
time, while in multiprogramming the prime focus is to maximize the CPU
usage.

22. MULTIPROCESSOR SYSTEMS
• A multiprocessor system consists of several processors
that share a common physical memory. Multiprocessor
system provides higher computing power and speed. In
multiprocessor system all processors operate under single
operating system. Multiplicity of the processors and how
they do act together are transparent to the others.
• Following are some advantages of this type of system.
– Enhanced performance
– Execution of several tasks by different processors
concurrently, increases the system's throughput without
speeding up the execution of a single task.
– If possible, system divides task into many subtasks and
then these subtasks can be executed in parallel in
different processors. Thereby speeding up the execution
of single tasks.

23. DISTRIBUTED OPERATING SYSTEMS
• The motivation behind developing distributed
operating systems is the availability of powerful
and inexpensive microprocessors and advances
in communication technology.
• These advancements in technology have made it
possible to design and develop distributed
systems comprising of many computers that are
inter connected by communication networks. The
main benefit of distributed systems is its low
price/performance ratio.

24. REAL-TIME OPERATING
SYSTEM
• Real time system is defines as a data processing system
in which the time interval required to process and respond
to inputs is so small that it controls the environment.
• Hard real-time systems guarantee that critical tasks
complete on time. In hard real-time systems secondary
storage is limited or missing with data stored in ROM.
• Soft real time systems are less restrictive. Critical real-time
task gets priority over other tasks and retains the priority
until it completes.
• For example, Multimedia, virtual reality, Advanced
Scientific Projects like undersea exploration and planetary
rovers etc.

25. OS Services
• An Operating System provides services to
both the users and to the programs.
–It provides programs, an environment to
execute.
–It provides users, services to execute the
programs in a convenient manner.

26. • Following are few common services provided by
operating systems.
– Program execution
– I/O operations
– File System manipulation
– Communication
– Error Detection
– Resource Allocation
– Protection

27.  Program execution:
• Operating system handles many kinds of activities from
user programs to system programs like printer spooler,
name servers, file server etc. Each of these activities is
encapsulated as a process.
• A process includes the complete execution context (code to
execute, data to manipulate, registers, OS resources in
use).
• Following are the major activities of an operating system
with respect to program management.
– Loads a program into memory.
– Executes the program.
– Handles program's execution.
– Provides a mechanism for process synchronization.
– Provides a mechanism for process communication.
– Provides a mechanism for deadlock handling.

28.  I/O Operation:
• I/O subsystem comprised of I/O devices and their
corresponding driver software.
• Drivers hides the peculiarities of specific hardware devices
from the user as the device driver knows the peculiarities
of the specific device.
• Operating System manages the communication between
user and device drivers.
• Following are the major activities of an operating system
with respect to I/O Operation.
– I/O operation means read or write operation with any
file or any specific I/O device.
– Program may require any I/O device while running.
– Operating system provides the access to the required
I/O device when required.

29.  File system manipulation:
• A file represents a collection of related information. Computer can store
files on the disk (secondary storage), for long term storage purpose.
Few examples of storage media are magnetic tape, magnetic disk and
optical disk drives like CD, DVD. Each of these media has its own
properties like speed, capacity, data transfer rate and data access
methods.
• A file system is normally organized into directories for easy navigation
and usage. These directories may contain files and other directions.
Following are the major activities of an operating system with respect to
file management.
• Program needs to read a file or write a file.
• The operating system gives the permission to the program for
operation on file.
• Permission varies from read-only, read-write, denied and so on.
• Operating System provides an interface to the user to create/delete
files.
• Operating System provides an interface to the user to create/delete
directories.
• Operating System provides an interface to create the backup of file

30.  Communication:
• In case of distributed systems which are a collection of
processors that do not share memory, peripheral devices,
or a clock, operating system manages communications
between processes. Multiple processes with one another
through communication lines in the network.
• OS handles routing and connection strategies, and the
problems of contention and security.
• Following are the major activities of an operating system
with respect to communication.
– Two processes often require data to be transferred
between them.
– The both processes can be on the one computer or on
different computer but are connected through computer
network.
– Communication may be implemented by two methods
either by Shared Memory or by Message Passing.

31. Error handling:
• Error can occur anytime and anywhere. Error may
occur in CPU, in I/O devices or in the memory
hardware.
• Following are the major activities of an operating
system with respect to error handling.
– OS constantly remains aware of possible errors.
– OS takes the appropriate action to ensure
correct and consistent computing.

32. Resource Management:
• In case of multi-user or multi-tasking environment,
resources such as main memory, CPU cycles and
files storage are to be allocated to each user or
job.
• Following are the major activities of an operating
system with respect to resource management.
– OS manages all kind of resources using
schedulers.
– CPU scheduling algorithms are used for better
utilization of CPU.

33.  Protection:
• Considering a computer systems having multiple users the
concurrent execution of multiple processes, then the various
processes must be protected from each another's activities.
• Protection refers to mechanism or a way to control the
access of programs, processes, or users to the resources
defined by a computer systems.
• Following are the major activities of an operating system
with respect to protection.
– OS ensures that all access to system resources is
controlled.
– OS ensures that external I/O devices are protected from
invalid access attempts.
– OS provides authentication feature for each user by
means of a password.

34. • System Call:
• A system call is how a program requests a
service from an operating system's kernel.
• These calls are generally available as routines
written in C and C++.
• Interface between a process and the operating
system kernel.

36. • System calls are expensive.
• The system needs to perform many things
before executing a system call.
– The computer (hardware) saves its state
– The OS code takes control of the CPU,
privileges are updated.
– The OS examines the call parameters
– The OS performs the requested function
– The OS saves its state (and call results)
– The OS returns control of the CPU to the caller

37. • Steps for Making a System Call
(Example: read call):

39. • Example:
• getuid() //get the user ID
• fork() //create a child process
• exec() //executing a program

40. Types of System Calls
• There are 5 different categories of system
calls:
• process control, file manipulation, device
manipulation, information maintenance
and communication.

41. • Process Control:
– A running program needs to be able to stop execution either
normally or abnormally. When execution is stopped abnormally,
often a dump of memory is taken and can be examined with a
debugger.
• File Management:
– Some common system calls
are create, delete, read, write, reposition, or close. Also, there is a
need to determine the file attributes – get and set file attribute.
Many times the OS provides an API to make these system calls.
• Device Management:
– Process usually require several resources to execute, if these
resources are available, they will be granted and control returned to
the user process. These resources are also thought of as devices.
Some are physical, such as a video card, and others are abstract,
such as a file.
– User programs request the device, and when finished
they release the device. Similar to files, we can read, write,
and reposition the device.

42. • Information Management:
– Some system calls exist purely for transferring information
between the user program and the operating system. An example
of this is time, or date.
– The OS also keeps information about all its processes and
provides system calls to report this information.
• Communication:
– There are two models of interprocess communication, the
message-passing model and the shared memory model.
– Message-passing uses a common mailbox to pass messages
between processes.
– Shared memory use certain system calls to create and gain
access to regions of memory owned by other processes. The two
processes exchange information by reading and writing in the
shared data.

46. Layered Operating System
The operating system is
divided into a number of
layers (levels), each built
on top of lower layers. The
bottom layer (layer 0), is
the hardware; the highest
(layer N) is the user
interface.
With modularity, layers
are selected such that
each uses functions
(operations) and services
of only lower-level layers

47. Layered Structure
Hardware
Level 1
Level 2
Level N
...
• Hiding information at each
layer
• Develop a layer at a time
• The Nth
layer can access
services provided by the
(N-1)th
layer and provide
services to the (N+1)th
layer.
• Examples
– THE (6 layers)
– MS-DOS (4 layers)

48. Continue…
• One advantage of a layered operating system
structure is that each layer of code is given access
to only the lower level interfaces(and data
structures).
• This structure also allow the OS to be debugged
starting at the lowest level, adding one layer at a
time until the whole system works correctly.
• Layering also makes it easier to enhance the OS.
• One entire layer can be replaced without affecting
other parts of the system.
• Layered OS delivers low application performance
in comparison to monolithic OS.

49. Microkernel System Structure

50. µ−kernel
entry
User
program
Services
call
return

53. Monolithic System Structure
• Traditional UNIX OS uses
monolithic kernel
architecture.
• The entire OS runs as a
single program in kernel
mode.
• All kernel routines are
together.
• A system call interface
• Examples:
– Linux
– Most Unix OS
– NT
Kernel
many many things
entry
User
program
User
program
call
return

55. It is the oldest architecture used for developing operating system.
Operating system resides on kernel for anyone to execute.
System call is involved i.e. Switching from user mode to kernel mode
and transfer control to operating system shown as event 1.
Many CPU has two modes, kernel mode, for the operating system in
which all instruction are allowed and user mode for user program in which
I/O devices and certain other instruction are not allowed.
Two operating system then examines the parameter of the call to
determine which system call is to be carried out shown in event 2.
Next, the operating system index’s into a table that contains procedure
that carries out system call.
This operation is shown in events. Finally, it is called when the work has
been completed and the system call is finished, control is given back to the
user mode as shown in event 4.

57. Comparison
Sr.
No.
Monolithic Kernel Microkernel
1. Kernel size is large. Kernel size is small.
2. OS is complex to design. OS is easy to design, implement and
install.
3. Request may be services faster. Request may be serviced slower than
monolithic kernel.
4. All the OS services are included in
the kernel.
Kernel provides only IPC and low level
device management services.
5. No message passing and non context
switching are required while the
kernel is performing the job.
Microkernel requires message passing
and context switches.

58. Virtual Machines
• Virtual machine is an illusion of a real machine.
• It is created by a real machine operating system, which
make a single real machine appears to be several real
machine.
• The architecture of virtual machine is shown above.
• The best example of virtual machine architecture is IBM
370 computer.
• In this system each user can choose a different operating
system.

59. • Actually, virtual machine can run several operating systems at
once, each of them on its virtual machine.
• Its multiprogramming shares the resource of a single machine in
different manner.
The concepts of virtual machine are:-
a. Control program (cp):- cp creates the environment in which
virtual machine can execute. It gives to each user facilities of real
machine such as processor, storage I/0 devices.
b. conversation monitor system (cons):- cons is a system application
having features of developing program. It contains editor,
language translator, and various application packages.
c. Remote spooling communication system (RSCS):- provide virtual
machine with the ability to transmit and receive file in distributed
system.
d. IPCS (interactive problem control system):- it is used to fix the
virtual machine software problems.