OPERATING SYSTEM-STRUCTURE AND UNIT 1.pptx

MULTIPROCESSOR AND MULTICORE
ORGANIZATION
ABINAYA.R / AP / CSE / SRIT
▶Multiprocessor Operating System refers to the use
of two or more central processing units (CPU) within a
single computer system.
These multiple CPUs are in a close communication
sharing the computer bus,memory and other
peripheral devices.
These systems are referred as tightly coupled
systems.

MULTICORE
•A single computing component with multiple
cores (independent processing units) is known as a
multicore processor.
• It denotes the presence of a single CPU with several
cores in the system
•These cores may execute normal processors instructions,
including add, move data, and branch increasing the
overall speed of the system's program execution.
• It decreases the amount of heat generated by the CPU
while enhancing the speed with which instructions are
executed.

Features Multiprocessors Multicore
Definition It is a system with multiple CPUs
that allows processing programs
simultaneously.
A multicore processor is a single
processor that contains multiple
independent processing units
known as cores that may read and
execute program instructions.
Execution Multiprocessors run multiple
programs faster than a multicore
system.
The multicore executes a single
program faster.
Reliability It is more reliable than the
multicore system. If one of any
processors fails
in the system, the other
processors
will not be affected.
It is not much reliable than the
multiprocessors.
Traffic It has high traffic than the multicore
system.
It has less traffic than the
multiprocessors.
Cost It is more expensive as compared to
a multicore system.
These are cheaper than the
multiprocessors system.
Configuration It requires complex configuration. It doesn't need to be configured.

Various Evolution of the Operating System

1. Serial Processing
▶ It develops by 1940 to 1950’s programmers
incorporated by the hardware components
without the implementation of the operating
system. The problems here are the
scheduling and setup time. The user’s login
for machine time by wasting the computed
time. The setup time is involved when loading
the compiler, saving the compiled program,
source program, linking and buffering. If any
intermediate error occurs, the process gets
starts over.

2. The Batch System
▶ The program is written in the punch cards and then
copied to the processing unit of the tape. When the
computer completed a single job, it instantly begins
the next task on the tape
▶ The first computers employed in the batch
operation method created a computer batch of
jobs that never paused or stopped.
When the computer finishes one job, it
immediately moves on to the next item on the
tape.
▶
Example: MVS Operating System of IBM is an
example of a batch processing operating system.

3. Multi-programmed Batch System
▶ It is used to have several jobs to execute
which should be held in main memory.
Job scheduling is made up of the processor
to decide which program to execute.
▶ Example: Windows and IOS are
examples of multi- programmed
batched operating systems.

Time-Sharing Operating System
•
▶ Printing ports were required for
programs having a command-line user
interface, which required written responses
to prompts or written commands. The
interaction is scrolled down like a roll of
paper. It was previously used to develop
batch replacement systems.
Multiple programs use time-sharing systems
to apply to the computer system by sharing
the system interactively.
• ▶ Example: Unix Operating System is an
example of a time-sharing OS.

5. Macintosh Operating System
▶ In 1960, the photo shows a Sutherland
pioneer program sketchpad is developed by
using many characteristics of the modern
graphical user interface but the hardware
components cost around millions of
dollars that occupied a room.
▶ Example: Mac OS X 10.6.8 snow leopard and OS X
10.7.5 Lion are some examples of macintosh OS.

computer structure

Input Unit
Central Processing Unit
Control Unit
Memory Unit
Output Unit

▶ Although it doesn’t receive any input from the outside world, it sends out
commands to other components, like the register and instruction decoder.
A computer’s control unit is the master of everything that goes on inside.
It handles everything from executing instructions to running programs.
▶ There are two main types of memory: random access memory (RAM) and
read-only memory (ROM).
▶ RAM stores data as it is being used, while ROM retains data even when
power isn't provided.
here’s another component involved in the processing of data: the control
unit.

Os stucture
▶ Simple structure:
▶ Such operating systems do not have well defined
structure and are small, simple and limited systems.
The interfaces and levels of functionality are not well
separated. MS-DOS is an example of such operating
system. In MS-DOS application programs are able to
access the basic I/O routines. These types of operating
system cause the entire system to crash if one of the
user programs fails.
▶ Diagram of the structure of MS-DOS is shown below.

▶ Advantages of Simple structure:
▶ It delivers better application performance because of the
few interfaces between the application program and the
hardware.
▶ Easy for kernel developers to develop such an operating
system.
▶ Disadvantages of Simple structure:
▶ The structure is very complicated as no clear boundaries
exists between modules.
▶ It does not enforce data hiding in the operating system.

▶ Layered structure:
▶ An OS can be broken into pieces and retain much more control on
system. In this structure the OS is broken into number of layers
(levels). The bottom layer (layer 0) is the hardware and the
topmost layer (layer N) is the user interface. These layers are so
designed that each layer uses the functions of the lower level
layers only. This simplifies the debugging process as if lower level
layers are debugged and an error occurs during debugging then the
error must be on that layer only as the lower level layers have
already been debugged.
▶ The main disadvantage of this structure is that at each layer, the
data needs to be modified and passed on which adds overhead to
the system. Moreover careful planning of the layers is necessary
as a layer can use only lower level layers. UNIX is an example of
this structure.

▶ Advantages of Layered structure:
▶ Layering makes it easier to enhance the operating system as
implementation of a layer can be changed easily without
affecting the other layers.
▶ It is very easy to perform debugging and system verification.
▶ Disadvantages of Layered structure:
▶ In this structure the application performance is degraded
as compared to simple structure.
▶ It requires careful planning for designing the layers as higher
layers use the functionalities of only the lower layers.

Monolithic kernel
▶ A monolithic kernel is an operating system architecture where
the entire operating system is working in kernel space. The
monolithic model differs from other operating system
architectures, such as the microkernel architecture, in that it
alone defines a high-level virtual interface over computer
hardware.
▶ CP/M and DOS are simple examples of monolithic operating
systems. Both CP/M and DOS are operating systems that share
a single address space with the applications.

Micro-kernel:
▶ This structure designs the operating system by
removing all non-essential components from the
kernel and implementing them as system and user
programs. This result in a smaller kernel called the
micro-kernel.
▶ Advantages of this structure are that all new services
need to be added to user space and does not require
the kernel to be modified. Thus it is more secure and
reliable as if a service fails then rest of the operating
system remains untouched. Mac OS is an example of this
type of OS.

Modular structure or approach:
▶ It is considered as the best approach for an OS. It
involves designing of a modular kernel. The kernel has
only set of core components and other services are
added as dynamically loadable modules to the kernel
either during run time or boot time. It resembles
layered structure due to the fact that each kernel has
defined and protected interfaces but it is more flexible
than the layered structure as a module can call any
other module.
▶ For example Solaris OS is organized as shown in the
figure.

Components of operating
system

Process Management :
▶ Process Management :
▶ A process is a program in execution. It consists of the
followings:
▶ Executable program
▶ Program’s data
▶ Stack and stack pointer
▶ Program counter and other CPU registers
▶ Details of opened files

▶ A process can be suspended temporarily and the execution of another
process can be taken up. A suspended process can be restarted later.
Before suspending a process, its details are saved in a table called the
process table so that it can be executed later on. An operating system
supports two system calls to manage processes Create and Kill –
▶ Create a system call used to create a new process.
▶ Kill system call used to delete an existing process.
▶ A process can create a number of child processes. Processes can
communicate among themselves either using shared memory or by
message-passing techniques. Two processes running on two different
computers can communicate by sending messages over a network.

Files Management :
▶ Files are used for long-term storage. Files are used for both input
and output. Every operating system provides a file management
service. This file management service can also be treated as an
abstraction as it hides the information about the disks from the user.
The operating system also provides a system call for file
management. The system call for file management includes –
▶ File creation
▶ File deletion
▶ Read and Write operations
▶ Files are stored in a directory. System calls provide to put a file in a
directory or to remove a file from a directory. Files in the system are
protected to maintain the privacy of the user. Below shows the
Hierarchical File Structure directory.

Command Interpreter :
• ▶ There are several ways for users to interface with the operating system. One of
the approaches to user interaction with the operating system is through commands.
Command interpreter provides a command-line interface. It allows the user to enter a
command on the command line prompt (cmd). The command interpreter accepts and
executes the commands entered by a user. For example, a shell is a command
interpreter under UNIX. The commands to be executed are implemented in two ways:
• ▶ The command interpreter itself contains code to be executed.
• ▶ The command is implemented through a system file. The necessary system file is
loaded into memory and executed.

System Calls :
▶ System calls provide an interface to the services made by an operating system. The
user interacts with the operating system programs through System calls. These calls
are normally made available as library functions in high-level languages such as C,
Java, Python etc. It provides a level of abstraction as the user is not aware of the
implementation or execution of the call made. Details of the operating system is
hidden from the user. Different hardware and software services can be availed
through system calls.
▶ System calls are available for the following operations:
▶ Process Management
▶ Memory Management
▶ File Operations
▶ Input / Output Operations

Signals :
▶ Signals are used in the operating systems to notify a process that a
particular event has occurred. Signals are the software or hardware
interrupts that suspend the current execution of the task. Signals are
also used for inter-process communication. A signal follows the following
pattern :
▶ A signal is generated by the occurrence of a particular event it can be
the clicking of the mouse, the execution of the program successfully
or an error notifying, etc.
▶ A generated signal is delivered to a process for further execution.
▶ Once delivered, the signal must be handled.
▶ A signal can be synchronous and asynchronous which is handled by
a default handler or by the user-defined handler.
▶ The signal causes temporarily suspends the current task it was
processing, saves its registers on the stack, and starts running a special
signal handling procedure, where the signal is assigned to it.

Network Management :
▶ In today’s digital world, the complexity of networks and
services has created modern challenges for IT professionals
and users. Network management is a set of processes and
procedures that help organizations to optimize their
computer networks. Mainly, it ensures that users have the
best possible experience while using network applications
and services.
▶ Network management is a fundamental concept of
computer networks. Network Management Systems is a
software application that provides network administrators
with information on components in their networks. It
ensures the quality of service and availability of network
resources. It also examines the operations of a network,
reconstructs its network configuration, modifies it for
improving performance of tasks.

Security Management:
▶ The security mechanisms in an operating system ensure
that authorized programs have access to resources, and
unauthorized programs have no access to restricted
resources. Security management refers to the various
processes where the user changes the file, memory,
CPU, and other hardware resources that should have
authorization from the operating system.

I/O Device Management
▶ The I/O device management component is an I/O manager that hides the
details of hardware devices and manages the main memory for devices
using cache and spooling. This component provides a buffer cache and
general device driver code that allows the system to manage the main
memory and the hardware devices connected to it. It also provides and
manages custom drivers for particular hardware devices.
▶ The purpose of the I/O system is to hide the details of hardware devices
from the application programmer. An I/O device management component
allows highly efficient resource utilization while minimizing errors and
making programming easy on the entire range of devices available in
their systems.

Secondary Storage Management :
• ▶ Broadly, the secondary storage area is any space, where data is
stored permanently and the user can retrieve it easily. Your
computer’s hard drive is the primary location for your files and
programs. Other spaces, such as CD-ROM/DVD drives, flash memory
cards, and networked devices, also provide secondary storage for
data on the computer. The computer’s main memory (RAM) is a
volatile storage device in which all programs reside, it provides only
temporary storage space for performing tasks. Secondary storage
refers to the media devices other than RAM (e.g. CDs, DVDs, or hard
disks) that provide additional space for permanent storing of data
and software programs which is also called non- volatile storage.

Main memory management :
▶ Main memory is a flexible and volatile type of storage device. It is a
large sequence of bytes and addresses used to store volatile data. Main
memory is also called Random Access Memory (RAM), which is the
fastest computer storage available on PCs. It is costly and low in terms
of storage as compared to secondary storage devices. Whenever
computer programs are executed, it is temporarily stored in the main
memory for execution. Later, the user can permanently store the data
or program in the secondary storage device.

Following are the services provided
by an operating system -
• Program execution
• Input/output devices
▶ File Management
• Error Detection and Response
▶ Communication
• Security and Protection
▶ Program creation
▶ Accounting

▶ Program execution
▶ To execute a program, several tasks need to be performed. Both the
instructions and data must be loaded into the main memory. In addition,
input-output devices and files should be initialized, and other resources
must be prepared. The Operating structures handle these kinds of tasks.
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.
▶ Input/output devices
▶ As there are numerous types of I/O devices within the computer system,
and each I/O device calls for its own precise set of instructions for the
operation..
▶ An Operating System manages the communication between user and
device drivers.
▶ I/O operation means read or write operation with any file or any specific
I/O device.
▶ Operating system provides the access to the required I/O device when
required.

File management
▶ Computers keep data and information on secondary storage devices like
magnetic tape, magnetic disk, optical disk, etc. Each storage media has its
capabilities like speed, capacity, data transfer rate, and data access
methods.
▶ For file management, the operating system must know the types of
different files and the characteristics of different storage devices. It has to
offer the proportion and safety mechanism of documents additionally.
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 system.

Communication
▶ The operating system manages the exchange of data and
programs among different computers connected over a network.
This communication is accomplished using message passing and
shared memory.
▶ Error Detection and Response
▶ Errors can occur anytime and anywhere. An 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 −
▶ The OS constantly checks for possible errors.
▶ The OS takes an appropriate action to ensure correct and
consistent computing.

▶ Program Creation
▶ The Operating system offers the structures and tools, including
editors and debuggers, to help the programmer create,
modify, and debugging programs.

▶ Security and Protection
▶ Operating device affords safety to the statistics and packages
of a person and protects any interference from unauthorized
users. The safety feature counters threats, which are
published via way of individuals out of doors the manage of
the running device.
▶ The OS ensures that all access to system resources is
controlled.
▶ The OS ensures that external I/O devices are protected
from invalid access attempts.
▶ The OS provides authentication features for each user
by means of passwords.

What is a System Call?
▶ A system call is a method for a computer program to request a
service from the kernel of the operating system on which it is
running. A system call is a method of interacting with the
operating system via programs. A system call is a request from
computer software to an operating system's kernel.
▶ The Application Program Interface (API) connects the
operating system's functions to user programs. It acts as a link
between the operating system and a process, allowing user-
level programs to request operating system services. The
kernel system can only be accessed using system calls. System
calls are required for any programs that use resources.

▶ Types of System
Calls
▶
▶
▶
▶
System calls can be grouped roughly into six major categories: process
control, file manipulation, device manipulation, information maintenance,
communications, and protection
▶ A running program needs to be able to halt its execution either normally
(end()) or abnormally (abort()). If a system call is made to terminate the currently
running program abnormally, or if the program runs into a problem and causes
an error trap, a dump of memory is sometimes taken and an error message
generated. The dump is written to disk and may be examined by a debugger—a
system program designed to aid the programmer in finding and correcting
errors, or bugs—to determine the cause of the problem. Under either normal or
abnormal circumstances, the operating system must transfer control to the
invoking command interpreter. The command interpreter then reads the next
command. In an interactive system, the command interpreter simply continues
with the next command; it is assumed that the user will issue an appropriate
command to respond to any error. In a GUI system, a pop-up window might alert
the user to the error and ask for guidance. In a batch system, the command
interpreter usually terminates the entire job and continues with the next job.
Some systems may allow for special recovery actions in case an error occurs. If
the program discovers an error in its input and wants to terminate abnormally, it
may also want to define an error level. More severe errors can be indicated by a
higher-level error parameter. It is then possible to combine normal and abnormal
termination by defining a normal termination as an error at level 0. The
command interpreter or a following program can use this error level to determine
the next action automatically.

▶ Process control
▶ ◦ end, abort
▶ ◦ load, execute
▶ ◦ create process, terminate process
▶ ◦ get process attributes, set process
attributes
▶ ◦ wait for time
▶ ◦ wait event, signal event
▶ ◦ allocate and free memory
▶ • File management
▶ ◦ create file, delete file
▶ ◦ open, close
▶ ◦ read, write, reposition
▶ ◦ get file attributes, set file attributes
▶ • Device management
▶ ◦ request device, release device
▶ ◦ read, write, reposition
▶ ◦ get device attributes, set device attributes
▶ ◦ logically attach or detach devices
▶ • Information maintenance
▶ ◦ get time or date, set time or date
▶ ◦ get system data, set system data
▶ ◦ get process, file, or device attributes
▶ ◦ set process, file, or device attributes
▶ • Communications
▶ ◦ create, delete communication connection
▶ ◦ send, receive messages
▶ ◦ transfer status information
▶ ◦ attach or detach remote devices

ABIN
Process Windows Unix
Process Control CreateProcess()
ExitProcess()
WaitForSingleObject() Wait()
Fork()
Exit()
File Manipulation CreateFile()
ReadFile()
WriteFile()
CloseHandle() Close()
Open()
Read()
Write()
Device Management SetConsoleMode()
ReadConsole()
WriteConsole() Write()
Ioctl()
Read()
Information Maintenance GetCurrentProcessID()
SetTimer()
Sleep() Sleep()
Getpid()
Alarm()
Communication CreatePipe()
CreateFileMapping()
MapViewOfFile() Mmap()
Pipe()
Shmget()
Protection
AYA.R / AP / CSE / SRIT
SetFileSecurity()
InitializeSecurityDescriptor()
SetSecurityDescriptorgr
oup()
Chown()
Chmod()
Umask()

System programs
▶ In an operating system a user is able to use different types of
system programs and the system program is responsible for all
the application software performance of the computer.
▶ The system programs are responsible for the development and
execution of a program and they can be used by the help of
system calls because system calls define different types of
system programs for different tasks.

Types of System programs
▶ The types of system programs are as follows −
▶ Utility program
▶ It manages, maintains and controls various computer resources. Utility
programs are comparatively technical and are targeted for the users with solid
technical knowledge.
▶ Few examples of utility programs are: antivirus software, backup software and
disk tools.
▶ Device drivers
▶ It controls the particular device connected to a computer system. Device
drivers basically act as a translator between the operating system and device
connected to the system.
▶ Example − printer driver, scanner driver, storage device driver etc.
▶ Directory reporting tools
▶ These tools are required in an operation system to have some software to
facilitate the navigation through the computer system.
▶ Example − dir, ls, Windows Explorer etc.

OS Generation
▶ The First Generation ( 1945 - 1955 ): Vacuum Tubes and Plugboards
▶ Digital computers were not constructed until the second world war. Calculating engines with
mechanical relays were built at that time. However, the mechanical relays were very slow
and were later replaced with vacuum tubes. These machines were enormous but were still
very slow.
▶ These early computers were designed, built and maintained by a single group of people.
Programming languages were unknown and there were no operating systems so all the
programming was done in machine language. All the problems were simple numerical
calculations.
▶ By the 1950’s punch cards were introduced and this improved the computer system. Instead
of using plugboards, programs were written on cards and read into the system.
▶ The Second Generation ( 1955 - 1965 ): Transistors and Batch Systems
▶ Transistors led to the development of the computer systems that could be manufactured
and sold to paying customers. These machines were known as mainframes and were locked
in air-conditioned computer rooms with staff to operate them.
▶ The Batch System was introduced to reduce the wasted time in the computer. A tray full of
jobs was collected in the input room and read into the magnetic tape. After that, the tape
was rewound and mounted on a tape drive. Then the batch operating system was loaded in
which read the first job from the tape and ran it. The output was written on the second
tape. After the whole batch was done, the input and output tapes were removed and the
output tape was printed.

▶ The Third Generation ( 1965 - 1980 ): Integrated Circuits
and Multiprogramming
▶ Until the 1960’s, there were two types of computer systems i.e the
scientific and the commercial computers. These were combined by IBM in
the System/360. This used integrated circuits and provided a major price
and performance advantage over the second generation systems.
▶ The third generation operating systems also introduced multiprogramming.
This meant that the processor was not idle while a job was completing its
I/O operation. Another job was scheduled on the processor so that its time
would not be wasted.
▶ The Fourth Generation ( 1980 - Present ): Personal Computers
▶ Personal Computers were easy to create with the development of large-
scale integrated circuits. These were chips containing thousands of
transistors on a square centimeter of silicon. Because of these,
microcomputers were much cheaper than minicomputers and that made it
possible for a single individual to own one of them.
▶ The advent of personal computers also led to the growth of networks. This
created network operating systems and distributed operating systems. The
users were aware of a network while using a network operating system and
could log in to remote machines and copy files from one machine to
another.

Booting in Operating System
▶ Booting is the process of starting a computer. It can be initiated by
hardware such as a button press or by a software command. After
it is switched on, a CPU has no software in its main memory, so
some processes must load software into memory before
execution. This may be done by hardware or firmware in
the CPU or by a separate processor in the computer system.
▶ Restarting a computer also is called rebooting, which can be
"hard", e.g., after electrical power to the CPU is switched from off
to on, or "soft", where the power is not cut. On some systems, a
soft boot may optionally clear RAM to zero. Hard and soft booting
can be initiated by hardware such as a button press or a software
command. Booting is complete when the operative runtime
system, typically the operating system and some applications, is
attained.

1. Cold Booting: When the computer starts for the first time or is in a
shut-down state and switch on the power button to start
the system, this type of process to start the computer is called
cold booting. During cold booting, the system will
read all the instructions from the ROM (BIOS) and the
Operating System will be automatically get loaded into the
system. This booting takes more time than Hot or Warm
Booting.
2. Warm Booting: Warm or Hot Booting process is when computer
systems come to no response or hang state, and then the
system is allowed to restart during on condition. It is also
referred to as rebooting. There are many reasons for this
state, and the only solution is to reboot the computer.
Rebooting may be required when we install new software or
hardware. The system requires a reboot to set software or
hardware configuration changes, or sometimes systems may
behave abnormally or may not respond properly. In such
a case, the system has to be a force restart. Most
commonly Ctrl+Alt+Del button is used to reboot the system. Else,
in some systems, the external reset button may be available
to reboot the system.

▶ Booting Process in Operating System
▶ When our computer is switched on, it can be started by
hardware such as a button press, or by software command, a
computer's central processing unit (CPU) has no software in its
main memory, there is some process which must load
software into main memory before it can be executed. Below
are the six steps to describe the boot process in the operating
system, such as:

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