1. Chapter 1: Introduction
What is an Operating System?
Mainframe Systems
Desktop Systems
Multiprocessor Systems
Distributed Systems
Clustered System
Real -Time Systems
Handheld Systems
Computing Environments
Operating System Concepts

2. What is an Operating System?
A program that acts as an intermediary between a user of a computer and the computer hardware.
Operating system goals:
Execute user programs and make solving user problems easier.
Make the computer system convenient to use.
Use the computer hardware in an efficient manner.
Operating System Concepts

3. Operating System Concepts

4. Operating System Concepts

5. Operating System Concepts

6. controlling peripheral devices such as disk drives and printers.
Computer's operating system (OS) manages all of the software and hardware on the computer.
Most of the time, there are several different computer programs running at the same time, and they all need to access your computer's central processing unit (CPU), memory, and storage.
The operating system coordinates all of this to make sure each program gets what it needs.
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
controlling peripheral devices such as disk drives and printers.
Operating System Concepts

7. Operating System Concepts

8. Examples of computer operating systems
Microsoft Windows 7 - PC and IBM compatible operating system. Microsoft Windows is the most common and used operating system.
Apple MacOS - Apple Mac operating system. The only Apple computer operating system is MacOS.
Ubuntu Linux - A popular variant of Linux used with PC and IBM compatible computers.
Google Android - Operating system used with Android compatible phones.
iOS - Operating system used with the Apple iPhone.
Operating System Concepts

9. Operating System Concepts

10. The Classification of Operating systems
Multi-user: Allows two or more users to run programs at the same time. Some operating systems permit hundreds or even thousands of concurrent users.
Multiprocessing : Supports running a program on more than one CPU.
Multitasking : Allows more than one program to run concurrently.
Multithreading : Allows different parts of a single program to run concurrently.
Real time: Responds to input instantly. General-purpose operating systems, such as DOS and UNIX, are not real-time.
Operating System Concepts

11. Computer System Components
1. Hardware – provides basic computing resources (CPU, memory, I/O devices).
2. Operating system – controls and coordinates the use of the hardware among the various application programs for the various users.
3. Applications programs – define the ways in which the system resources are used to solve the computing problems of the users (compilers, database systems, video games, business programs).
4. Users (people, machines, other computers).
Operating System Concepts

12. Abstract View of System Components
Operating System Concepts

13. Operating System Concepts

14. Operating System Definitions
Resource allocator – manages and allocates resources.
Control program – controls the execution of user programs and operations of I/O devices .
Kernel – the one program running at all times (all else being application programs).
Operating System Concepts

15. The main tasks of the kernel are : Process management
What Is Kernel?
A kernel is a heart of an operating system. It acts as an interface between the user applications and the hardware.
The sole aim of the kernel is to manage the communication between the software (user level applications) and the hardware (CPU, disk memory etc).
The main tasks of the kernel are :
Process management
Device management
Memory management
Interrupt handling
I/O communication
File system...etc..
Operating System Concepts

16. Operating System Concepts

17. Is LINUX A Kernel Or An Operating System
Is LINUX A Kernel Or An Operating System? Well, there is a difference between kernel and OS.
Kernel as described above is the heart of OS which manages the core features of an OS.
While if some useful applications and utilities are added over the kernel, then the complete package becomes an OS.
So, it can easily be said that an operating system consists of a kernel space and a user space.
So, we can say that Linux is a kernel as it does not include applications like file-system utilities, windowing systems and graphical desktops, system administrator commands, text editors, compilers etc.
So, various companies add these kind of applications over linux kernel and provide their operating system like ubuntu, suse, fedora,centOS, redHat etc
Operating System Concepts

18. Operating System Concepts

19. This type of architecture led to some serious drawbacks like
Types Of Kernels
1 Monolithic Kernels
Earlier in this type of kernel architecture, all the basic system services like process and memory management, interrupt handling etc were packaged into a single module in kernel space.
This type of architecture led to some serious drawbacks like
1) Size of kernel, which was huge.
2)Poor maintainability, which means bug fixing or addition of new features resulted in recompilation of the whole kernel which could consume hours
In a modern day approach to monolithic architecture, the kernel consists of different modules which can be dynamically loaded and un-loaded.
Linux follows the monolithic modular approach
Operating System Concepts

20. Microkernels
This architecture majorly caters to the problem of ever growing size of kernel code which we could not control in the monolithic approach.
This architecture allows some basic services like device driver management, protocol stack, file system etc to run in user space.
This reduces the kernel code size and also increases the security and stability of OS as we have the bare minimum code running in kernel.
So, if suppose a basic service like network service crashes due to buffer overflow, then only the networking service's memory would be corrupted, leaving the rest of the system still functional.
Operating System Concepts

21. 1.5 What are the differences between Linux and UNIX?
Command-line-wise, almost none, although this has been changing (for better or worse). Linux has a much larger market appeal and following than any commercial UNIX. GUI-wise there are also no major differences--Linux, as most other UNIXes, uses an X-Windowing system.
The major differences:
Linux is free, while many UNICES (this is supposed to be the plural of UNIX), are very expensive. The same for applications--many good applications are available on Linux free. Even the same commercial application (if you wanted to buy one) typically costs much more for a commercial UNIX than for Linux.
Linux runs on many hardware platforms, the commodity Intel-x86/IBM-spec personal computers being the most prominent. In contrast, a typical UNIX is proprietary-hardware-bonded (and this hardware tends to be much more expensive than a typical PC clone).
With Linux, you are in charge of your computer, whereas on most UNICES you are typically confined to be an "l-user" (some administrators pronounce it "loser").
Linux feels very much like DOS/Win in the late 80s/90s, but is much sturdier and richer, while a typical UNIX account feels like a mainframe from the 60s/70s.
Some UNICES may be more mature in certain areas (for example, security, some engineering applications, better support of cutting-edge hardware). Linux is more for the average Joe who wants to run his own server or engineering workstation.
Operating System Concepts

22. OS EVOLUTION 1.Mainframe Systems
a).Batch Systems
Reduce setup time by batching similar jobs
Automatic job sequencing – automatically transfers control from one job to another. First rudimentary operating system.
Resident monitor
initial control in monitor
control transfers to job
when job completes control transfers back to monitor
Operating System Concepts

23. Memory Layout for a Simple Batch System
Operating System Concepts

24. b.)Multiprogrammed Batch Systems
Several jobs are kept in main memory at the same time, and the
CPU is multiplexed among them.
Operating System Concepts

25. OS Features Needed for Multiprogramming
I/O routine supplied by the system.
Memory management – the system must allocate the memory to several jobs.
CPU scheduling – the system must choose among several jobs ready to run.
Allocation of devices.
Operating System Concepts

26. C.)Time-Sharing Systems–Interactive Computing
On-line communication between the user and the system is provided; when the operating system finishes the execution of one command, it seeks the next “control statement” from the user’s keyboard.
The CPU is multiplexed among several jobs that are kept in memory and on disk (the CPU is allocated to a job only if the job is in memory).
A job swapped in and out of memory to the disk.
On-line system must be available for users to access data and code.
Operating System Concepts

27. 2.Desktop Systems
Personal computers – computer system dedicated to a single user.
I/O devices – keyboards, mice, display screens, small printers.
User convenience and responsiveness.
Can adopt technology developed for larger operating system’ often individuals have sole use of computer and do not need advanced CPU utilization of protection features.
May run several different types of operating systems (Windows, MacOS, UNIX, Linux)
Operating System Concepts

28. 3.Parallel Systems/Multiprocessor System
Multiprocessor systems with more than on CPU in close communication.
Tightly coupled system – processors share memory and a clock, bus, peripherals devices and ; communication usually takes place through the shared memory.
Advantages of parallel system:
Increased throughput
Economical
Increased reliability
graceful degradation:-The ability to continue providing service proportional to the level of surviving hardware
Fault tolerant:- System designed for graceful degradation
Operating System Concepts

29. Parallel Systems (Cont.)
Symmetric multiprocessing (SMP)
Each processor runs and identical copy of the operating system.
Many processes can run at once without performance deterioration.
Most modern operating systems support SMP
Eg. Windows , Mac OS X, Solaris version 5, unix design by sun microsystem
Asymmetric multiprocessing
Each processor is assigned a specific task; master processor schedules and allocated work to slave processors. Other processor look to the master for instruction and predefined task.
More common in extremely large systems
Eg.SunOS version 4
Operating System Concepts

30. Symmetric Multiprocessing Architecture
Operating System Concepts

31. 4.Distributed Systems
A distributed system is a collection of physically separate, possibly heterogeneous computer that are networked to provide the user with access to the various resources that system maintains.
It distributed the computation among several physical processors.
Loosely coupled system – each processor has its own local memory; processors communicate with one another through various communications lines, such as high-speed buses or telephone lines.
Advantages of distributed systems.
Resources Sharing
Computation speed up – load sharing
Reliability
Communications
Operating System Concepts

32. Distributed Systems (cont)
Requires networking infrastructure.
Local area networks (LAN) or Wide area networks (WAN)
May be either client-server or peer-to-peer systems.
Client Server are two type
Compute server system provide interface to which client can send request to perform action; in response the server execute the action and send back result to client eg. Database server
File Server System provide interface to which client can create, update, read, delete files. Eg. Web server.
In peer to peer, all nodes within the system are considered peers, and each may act as either client or server, depending on whether it is requesting and providing service
Service can be provided by several nodes distributed throughout the network
Operating System Concepts

33. General Structure of Client-Server
Operating System Concepts

34. 5.Clustered Systems
In Cluster system, two or more system coupled together to perform computational work.
Cluster computers share storage and closely linked via a LAN.
Provides high reliability.
Asymmetric clustering: one is in stand by mode while other is running the application. Stand by machine monitor the active server if server fail stand by host become active server.
Symmetric clustering: all N hosts are running the application and monitoring each other.
Operating System Concepts

35. 6.Real-Time Embedded Systems
System tend to have very specific task. It have little or no user interface, preferring to spend time in monitoring and managing hardware.eg. car engines, robots, microwave oven, washing machine.
Often used as a control device in a dedicated application such as controlling scientific experiments, medical imaging systems, industrial control systems, and some display systems.
Well-defined fixed-time constraints. Processing must be done within the defined constrained, or system will fail.
It functions correctly only if it return the correct result within its time constraints
Operating System Concepts

36. Real-Time Systems (Cont.)
Hard real-time:
Secondary storage limited or absent, data stored in short term memory, or read-only memory (ROM)
Conflicts with time-sharing systems, not supported by general-purpose operating systems.
Soft real-time
Limited utility in industrial control of robotics
Useful in applications (multimedia, virtual reality) requiring advanced operating-system features.
Operating System Concepts

37. 7.Handheld Systems Personal Digital Assistants (PDAs)
Cellular telephones
Issues:
Limited memory
Slow processors
Small display screens.
Operating System Concepts

38. Migration of Operating-System Concepts and Features

39. Computing Environments
Traditional computing
Web-Based Computing
Embedded Computing
Operating System Concepts