Advanced Operating
Systems
Application Software
(contd…):
Spreadsheets:
The spreadsheet packages are
designed to use numbers and formulas to do
calculations with ease. Examples of spreadsheets
include:
 Budgets
 Payrolls
 Grade Calculations
 Address Lists
The most commonly used spreadsheet programs are
Microsoft Excel and Lotus 123.
Application Software
(contd…):
Graphic Presentations:
The presentation
programs can be easier using overhead
projectors. Other uses include:
 Slide Shows
 Repeating Computer Presentations on a
computer monitor
 Using Sound and animation in slide shows
The most recognized graphic presentation programs are
Microsoft PowerPoint and Harvard Graphics.
Application Software
(contd…):
Database Management System (DBMS):



A DBMS is a software tool that allows multiple users to
store, access, and process data into useful information.
Database programs are designed for these types of
applications:
 Membership lists
 Student lists
 Grade reports
 Instructor schedules
All of these have to be maintained so you can find what
you need quickly and accurately.
Example:Microsoft Access, dBASE, Oracle.
Contents
1.
2.
3.
4.
What is Operating System?
What OS does?
Structure of OS
Evolution of OS

Batch Processing, Multiprogramming, Time
sharing systems
5. Operating System Functions
6. Main Functions of OS
7. Types of OS

Single User, Multi User systems
What is OS?

Operating System is a software, which makes a
computer to actually work.

It is the software the enables all the programs we use.

The OS organizes and controls the hardware.

OS acts as an interface between the application
programs and the machine hardware.

Examples: Windows, Linux, Unix and Mac OS, etc.,
What OS does?
An operating system performs basic tasks such as,

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controlling and allocating memory,
prioritizing system requests,
controlling input and output devices,
facilitating networking and
managing file systems.
Structure of Operating System:
Application Programs
System Programs
Software (Operating System)
HARDWARE
(Contd…)
Structure of Operating System
(Contd…):

The structure of OS consists of 4 layers:
1. Hardware
Hardware consists of CPU, Main memory, I/O
Devices, etc,
2.
Software (Operating System)
Software includes process management
routines, memory management routines, I/O
control routines, file management routines.
(Contd…)
Structure of Operating System
(Contd…):
3.
System programs
This layer consists of compilers, Assemblers,
linker, Loaders etc.
4.
Application programs
This is dependent on users need. Ex. Railway
reservation system, Bank database
management etc.,
Evolution of OS:

The evolution of operating systems went through seven
major phases.

Six of them significantly changed the ways in which
users accessed computers through the open shop, batch
processing, multiprogramming, timesharing, personal
computing, and distributed systems.

In the seventh phase the foundations of concurrent
programming were developed and demonstrated in
model operating systems.
(Contd…)
Evolution of OS (contd..):
Major
Phases
Technical
Innovations
Operating
Systems
Open Shop
The idea of OS
IBM 701 open shop
(1954)
Batch
Processing
Tape batching,
First-in, first-out
scheduling.
BKS system (1961)
Multiprogramming
Processor multiplexing,
Indivisible operations,
Demand paging,
Input/output spooling,
Priority scheduling,
Remote job entry
Atlas supervisor (1961),
Exec II system (1966)
(Contd…)
Evolution of OS (contd..):
Timesharing
Simultaneous user
interaction,
On-line file systems
Multics file system
(1965),
Unix (1974)
Concurrent
Programming
Hierarchical systems,
Extensible kernels,
Parallel programming
concepts, Secure parallel
languages
RC 4000 system (1969),
13 Venus system
(1972),
14 Boss 2 system
(1975).
Personal
Computing
Distributed
Systems
Graphic user interfaces
OS 6 (1972)
Pilot system (1980)
Remote servers
WFS file server (1979)
Unix United RPC (1982)
24 Amoeba system
(1990)
Batch Processing:

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In Batch processing same type of jobs batch (BATCH- a
set of jobs with similar needs) together and execute at a
time.
The OS was simple, its major task was to transfer control
from one job to the next.
The job was submitted to the computer operator in form
of punch cards. At some later time the output appeared.
The OS was always resident in memory. (Ref. Fig. next
slide)
Common Input devices were card readers and tape
drives.
Batch Processing (Contd…):


Common output devices were line printers, tape drives,
and card punches.
Users did not interact directly with the computer
systems, but he prepared a job (comprising of the
program, the data, & some control information).
OS
User
program
area
Multiprogramming:

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Multiprogramming is a technique to execute number of
programs simultaneously by a single processor.
In Multiprogramming, number of processes reside in
main memory at a time.
The OS picks and begins to executes one of the jobs in
the main memory.
If any I/O wait happened in a process, then CPU
switches from that job to another job.
Hence CPU in not idle at any time.
Multiprogramming (Contd…):
OS
Job 1
Job 2
Job 3
• Figure
dipicts the layout of
multiprogramming system.
• The main memory consists of 5
jobs at a time, the CPU executes
one by one.
Advantages:
Job 4
•Efficient memory utilization
Job 5
•Throughput increases
•CPU is never idle, so
performance increases.
Time Sharing Systems:

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Time sharing, or multitasking, is a logical extension of
multiprogramming.
Multiple jobs are executed by switching the CPU
between them.
In this, the CPU time is shared by different processes, so
it is called as “Time sharing Systems”.
Time slice is defined by the OS, for sharing CPU time
between processes.
Examples: Multics, Unix, etc.,
Operating Systems functions:

The main functions of operating systems are:
1. Program creation
2. Program execution
3. Input/Output operations
4. Error detection
5. Resource allocation
6. Accounting
7. protection
Types of OS:
Operating System can also be classified as,
Single User Systems

Multi User Systems
Single User Systems:

Provides a platform for only one user at a
time.

They are popularly associated with Desk Top
operating system which run on standalone
systems where no user accounts are
required.
Example: DOS

Multi-User Systems:

Provides regulated access for a number of users by
maintaining a database of known users.

Refers to computer systems that support two or more
simultaneous users.

Another term for multi-user is time sharing.

Ex: All mainframes and are multi-user systems.
Example: Unix

Operating Systems Structures

Structure/Organization/Layout of OSs:
1.
2.
3.
4.

Monolithic (one unstructured program)
Layered
Microkernel
Virtual Machines
The role of
Virtualization
Monolithic Operating System

A software system is called "monolithic" if it has a
monolithic architecture, in which functionally
distinguishable aspects (for example data input and output,
data processing, error handling, and the user interface), are
not architecturally separate components but are all
interwoven.

Mainframe computers used a monolithic architecture with considerable
success.

Monolithic architectures implemented on DOS and earlier Windows
based PCs often worked poorly with multiple users.

This performance degradation is mainly due to poor mechanisms for
record locking and file handling across local area networks.
Monolithic OS – basic structure



Application programs that invokes the
requested system services.
A set of system services that carry out the
operating system procedures/calls.
A set of utility procedures that help the
system services.
MS-DOS System Structure

MS-DOS – written to provide the most
functionality in the least space:


not divided into modules (monolithic).
Although MS-DOS has some structure, its
interfaces and levels of functionality are not well
separated.
MS-DOS Layer Structure
UNIX System Structure


UNIX – limited by hardware functionality, the
original UNIX OS had limited structuring.
The UNIX OS consists of two separable
parts:
1.
2.


Systems Programs:
The Kernel:
Consists of everything below the system-call
interface and above the physical hardware.
Provides the file system, CPU scheduling,
memory management, and other operatingsystem functions; a large number of functions for
one level.
Traditional UNIX System Structure
LINUX Kernel Components
Microkernel System Structure (1)


Move as much functionality as possible from
the kernel into “user” space.
Only a few essential functions in the kernel:

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primitive memory management (address space)
I/O and interrupt management
Inter-Process Communication (IPC)
basic scheduling
Other OS services are provided by processes
running in user mode (vertical servers):

device drivers, file system, virtual memory…
Microkernel System Structure (2)

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
Communication takes place between user
modules using message passing.
More flexibility, extensibility, portability and
reliability.
But performance overhead caused by
replacing service calls with message
exchanges between processes.
Microkernel Operating System
Benefits of a Microkernel Organization (1)

Extensibility/Reliability


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
easier to extend a microkernel
easier to port the operating system to new
architectures
more reliable (less code is running in kernel mode)
more secure
Portability

changes needed to port the system to a new
processor is done in the microkernel, not in the
other services.
Benefits of Microkernel Organization (2)
 Distributed

system support
message are sent without knowing
what the target machine is.
 Object-oriented

operating system
components are objects with clearly
defined interfaces that can be
interconnected to form software.
Layered Approach

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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.
Layered Operating System
General OS Layers
Operating System Layers
Structure of the THE operating system
Virtual Machines History and Benefits

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First appeared commercially in IBM mainframes in 1972.
Fundamentally, multiple protected execution environments
(different operating systems) can share the same hardware.
Protect from each other.
Some sharing of file can be permitted, controlled.
Commutate with each other, other physical systems via
networking.
Useful for development and testing.
“Open Virtual Machine Format”, standard format of VMs,
allows a VM to run within many different VM (host) platforms.
The Role of Virtualization
(a)
(b)
General organization between a program, interface, and
system.
General organization of virtualizing system A on top of
system B.
Virtual Machines (1)

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A Virtual Machine (VM) takes the layered and
microkernel approach to its logical conclusion.
It treats hardware and the operating system
kernel as though they were all hardware.
A virtual machine provides an interface identical
to the underlying bare hardware.
The operating system host creates the illusion
that a process has its own processor and (virtual
memory).
Each guest provided with a (virtual) copy of
underlying computer.
Virtual Machines (2)

The resources of the physical computer are
shared to create the virtual machines:



CPU scheduling can create the appearance that
users have their own processor.
Spooling and a file system can provide virtual card
readers and virtual line printers.
A normal user time-sharing terminal serves as the
virtual machine operator’s console.
VM Implementation on Host OS
Architectures of Virtual Machines (1)


There are interfaces at different levels.
An interface between the hardware and
software, consisting of machine instructions
that can be invoked by any program.

An interface between the hardware and
software, consisting of machine instructions

that can be invoked only by privileged
programs, such as an operating
system.
Architectures of Virtual Machines (2)


An interface consisting of system calls as
offered by an operating system.
An interface consisting of library calls:
 generally forming what is known as
an Application Programming Interface
(API).
 In many cases, the aforementioned
system calls are hidden by an API.
Architectures of Virtual Machines (3)
Various interfaces offered by computer systems
Process Virtual Machine
(a) A process virtual machine, with multiple
instances of (application, runtime)
combinations.
Java Virtual Machine



Compiled Java programs are platform-neutral
byte codes executed by a Java Virtual Machine
(JVM).
JVM consists of:
- class loader
- class verifier
- runtime interpreter
Just-In-Time (JIT) compilers increase
performance.
Advantages/Disadvantages of VMs



The VM concept provides complete protection of
system resources since each virtual machine is
isolated from all other virtual machines. This
isolation permits no direct sharing of resources.
A VM system is a perfect vehicle for OS research
and development. System development is done on
the virtual machine, instead of on a physical
machine and so does not disrupt normal system
operation.
The VM concept is difficult to implement due to the
effort required to provide an exact duplicate to the
underlying machine.
Types of OS

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Distributed Operating System( chap 2)
Multiprocessor Operating System(chap 3)
Real-Time Operating System(chap 4)
Database Operating System(chap 5)
Mobile Operating System(chap 6)
Why Advanced Operating Systems?

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Traditional Multitasking operating systems are
most commonly used at the user end
These conventional operating systems are unable
to provide high-speed computing
Multiprocessor systems and distributed systems
have been adopted for performance reasons
Enormously complex design issues
Network Operating Systems

Operating system, designed primarily to
support workstations, personal computer that
are connected on a local area network.

A network operating system provides printer
sharing, common file system and database
sharing, application sharing, and the ability to
manage a network name directory, security,
and other housekeeping aspects of a network.
Types of Advanced Operating Systems

Can be categorized on the following basis

Hardware Architecture

Wide variety of high-speed architecture is available




Multiprocessor systems
Distributed Systems
Offer great potential for speedup but also present great
challenge to OS designers
Application requirements

Some applications require special Operating system support
as requirement and for efficiency



Database systems
Real-time systems
Multimedia systems
Types of Advanced Operating Systems
Advanced Operating Systems
Architecture Driven
Distributed
Systems
Multiprocessor
systems
Application Driven
Database
Systems
Real-time
Systems
Distributed Operating Systems

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

Operating systems for a network of autonomous
computers connected by a communication network
Distributed Operating System controls and
manages the hardware and software resources of a
DS
Provides a view of a powerful computer system
Users do not know the where the program is
executed and the location of resources accessed
Basic issues are same as traditional OS
However, design is much more complex due to the
lack of both shared memory and common clock and
unpredictable communication delays
Multiprocessor Operating System


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
Multiprocessor system is a tightly coupled system
where processors share an address space
Consists of a set of processors that share a set of
physical memory
Multiprocessor OS controls and manages
hardware and software resources
Users view the system as a powerful uniprocessor
system
Process synchronization, task scheduling, memory
management and protection and security become
more complex as the Memory is shared by
processors
Database Operating System


Databases place special requirements on OS
It must support

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
The concept of transaction
Operations to store, retrieve and manipulate data
efficiently
Primitives for concurrency control
And system failure recovery
Should also have buffer management schemes
for data retrieval and storage from secondary
storage
Concurrency control is one of the most
challenging problems in the design of database
operating systems
Real-time Operating systems

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

Systems where jobs have completion deadlines
In soft real-time systems, jobs should be completed
before its deadline .
In hard real-time systems, jobs should be
completed before its deadline to avert a disaster
Jobs should be scheduled in such a way that a
maximum number of jobs satisfy their deadlines
Requirements can vary from application to
application
Mobile Operating System

Design and capabilities of a Mobile OS (Operating System) is
very different than a general purpose OS running on desktop
machines:

mobile devices have constraints and restrictions on their
physical characteristic such as screen size, memory,
processing power and etc.
 Scarce availability of battery power
 Limited
amount of computing and communication
capabilities
64

Thus, they need different types of operating systems
depending on the capabilities they support. e.g. a PDA OS is
different from a Smartphone OS.

Operating System is a piece of software responsible for
management of operations, control, coordinate the use of
the hardware among the various application programs, and
sharing the resources of a device.
65
Operating System Structure

A mobile OS is a software platform on top of which other
programs called application programs, can run on mobile
devices such as PDA, cellular phones, Smartphone and etc.
Applications
OS Libraries
Device Operating System Base, Kernel
Low-Level Hardware, Manufacturer Device Drivers
66
Mobile Operating System

There are many mobile operating systems. The followings
demonstrate the most important ones:
 Java ME Platform
 Palm OS
 Symbian OS
 Linux OS
 Windows Mobile OS
 BlackBerry OS
 iPhone OS
 Google Android Platform
67