Chapter 1 Operating System Environment Part 1
Chapter 1 Operating System Environment Part 1
Prepared by: Nor Zuraida Bt Mohd
Gaminan
Department of IT & Communication
Politeknik Tuanku Syed Sirajuddin Chapter Summary
At the end of this chapter, student will be able to: 1)
Defne operating system 2)
List the use of operating system in computer system 3) Describe various OS architecture 4) Describe various types of OS Introduction to Operating System (OS) Software program that controls the hardware.
Defnition of an operating system can be seen in four aspects:
1) A group of program that acts as an intermediary
between a user and the computer hardware.2)
Controls and co-ordinates the use of computer resources among various application programs and user.
3)
Acts as a manager
4) Allow the program to communicate with one
another Introduction to Operating System (OS)
Basically, two types of software available: 1) System software
- Groups of program that control the hardware
2) Application software
- Groups of programs that used by the end-user for
various applications such as text processing, spreadsheet, etc
OS categorized as system software
- Build to act as an intermediary between user of a computer and computer hardware
- Goal: Provide convenient and efcient environment for the user
User1 User2 User3 System and application programs Operating system Hardware
Figure 1: Abstract view of the components of a computer system Introduction to Operating System (OS)
Functions: 1) Resource Sharing
The OS contains a set of algorithms that allocates
- resources to the programs executed on behalf of the user. These resources include time, power, hardware, etc...
- 2) Control Program
- The control program controls the operation of the application programs to prevent errors afecting other programs.
3) Provision of a Virtual Machine
- This hides interfaces to I/O devices, fling systems, etc, and provides a programming interface for applications.
4) Kernel
- The kernel is the only program resident all the time (all other applications are application programs).
Introduction to Operating System (OS)
OS has three objectives: 1) Convenience
- An OS make a computer more convenient to be used
2) Efciency
- An OS allows the computer system resources to be used in an efcient manner
3) Ability to evolve
- - An OS is constructed in such a way to as to
permit the efective development, testing and introduction of new system function without at the same time interfering with service.
OPERATING SYSTEM ARCHITECTURE
This approach well known as “The Big Mess” - there is no structure.
All kernel routines are together, any can call any
A system call interface (main program, sys calls, utility functions)
Examples: Linux, BSD Unix, Windows
Pros
1) Shared kernel space
2) Good performance
Cons
1) No information hiding
2) Inflexible 3) Chaotic 4) Difcult to understand
1) Monolithic System
2) Layered 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. Hiding information at each layer E.g. level 1 is processor allocation, level 1 memory management, level 2 communication, level 3 I/O, etc. Examples: THE System (6 layers), MS-DOS (4 layers) Pros 1)
Layered abstraction 2) Separation of concerns, elegance Cons
1) Protection, boundary crossings
3) Client-server model or
microkernel
The advent of new concepts in OS design, microkernel is aimed
at migrating services of an operating system out of monolithic
kernel into user level process. Divide the OS into several processes, each which implements a single set of services
- Example: I/O servers, memory server, process server
Each server runs in user mode, provide services to the requested client.
Client: Another operating system component or application program, request service by sending message to server
An OS kernel (microkernel) running in kernel mode deliver message to the server.
The server perform operation, and microkernel delivers the result to client in another message. Client-server model or microkernel
Components above microkernel communicate directly with one another, although using message that pass through the microkernel itself.
Microkernel validate messages, passes them between the components and grants access to hardware.
Example: C-DAC microkernel, Mach, Windows NT, Chorus
Client-server model or
microkernelExample: Windows NT
Various applications (Win32, OS/2, and POSIX) run in user space.
Server for each application runs in user space.
Message passing between client application programs and application servers runs in kernel space.
OPERATING
SYSTEM TYPES
1) Batch Operating System
A batch system is one in which jobs are bundled together with the instructions necessary to allow them to be processed without intervention.
The basic physical layout of the memory of a batch job computer is shown below:
Monitor (permanently
resident)
User Space
The monitor is system software that is responsible for
(compilers, programs, data,
interpreting and carrying out the instructions in the
etc.)
batch jobs.- When the monitor starts a job, the entire computer is
Advantages:
1) Move much of the work of the operator to the
computer
2)
Increased performance since it was possible for job to start as soon as the previous job fnished
Disadvantages:
1) Due to lack of protection scheme, one batch job can
afect pending jobs (read too many cards, etc) Example: A job could corrupt the monitor, thus afecting pending jobs
2) A job could enter an infnite loop
2) Multiprogramming Operating
System
As machines with more and more memory became available, it was possible to extend the idea of multiprogramming (or multiprocessing) as used in batch systems.
This create a systems that would load several jobs into memory at once and cycle through them in some order, working on each one for a specifed period of time.
Monitor (more like an operating
The basic physical layout of a multiprogramming
system)
system is as shown:
User program 1 User program 2
At this point the monitor is growing to the point where it begins to resemble a modern operating system.
It is responsible for:
1)
Starting user jobs
2)
Spooling operations
3)
IO for user jobs
4)
Switching between user jobs
5)
Ensuring proper protection while doing the above
There are diferent type of Multiprogramming Operating System such as:
1) Multitasking Operating System
A type of multiprogramming operating system which can perform several process simultaneously.
The earliest multitasking OS available to home users was the AmigaOS.
All current major operating system support this feature.
2) Multi-user Operating System
A multi-user operating system allows for multiple users to use the same computer at the same time and/or diferent times.
Linux, Unix,Windows OS are some example of multitasking operating system.
3) Multiprocessing Operating System
An operating system capable of supporting and utilizing more than one computer.
4) Real Time Operating System
Often used as a control device in a dedicated application such as controlling scientifc experiments, medical imaging systems, industrial control systems, and some display systems.
Well-defned fxed-time constraints.
A Distributed Operating System is the one that runs on multiple, autonomous CPUs which provides its users an illusion of an ordinary Centralized Operating System that runs on a Virtual Uniprocessor.
Distributed Operating Systems provide resource transparency to the user processes.
“If you can tell which computer you are using, you are not using a distributed operating system.” -
Tanenbaum
3) Distributed Operating
System
The Distributed Operating System is unique and resides on diferent machines.
User processes can run on any of the CPUs as allocated by the Distributed Operating System.
Data can be resident on any machine that is the part of the Distributed System.
All multi-machine systems are not Distributed Systems.
“It is the software not the hardware that determines whether a system is distributed or not” - Tanenbaum
Advantages:
1) Price/Performance advantage (Availability of cheap and powerful Microprocessors).
2) Resources Sharing
3) Computation speed up – load sharing
4) Reliability and Availability. 5) Provides Transparency.
Disadvantages:
1) Lack of security - Easy access also applies to secret data.
An example of a distributed system: Amoeba An open source microkernel-based distributed
- operating system developed by Andrew S. Tanenbaum and others at the Vrije Universiteit. The aim of the Amoeba project is to build a
timesharing system that makes an entire network of
computers appear to the user as a single machine. Development seems to have stalled: the fles in thelatest version (5.3) were last modifed on 12 February
2001. Amoeba runs on several platforms, including i386,- i486, 68030, Sun 3/50 and Sun 3/60.
An example of a distributed system: Amoeba An open source microkernel-based distributed
- operating system developed by Andrew S. Tanenbaum and others at the Vrije Universiteit. The aim of the Amoeba project is to build a
timesharing system that makes an entire network of
computers appear to the user as a single machine. Development seems to have stalled: the fles in thelatest version (5.3) were last modifed on 12 February
2001. Amoeba runs on several platforms, including i386,- i486, 68030, Sun 3/50 and Sun 3/60.