1. Operating System Introduction
-Compiled for MCA
Ref: Tanenbaum, Modern Operating Systems 3 e, (c) 2008 Prentice-Hall, Inc.

2. Content Introduction of Operating System Functions of operating system
History of operating system
Types of operating system
Structure of operating system

3. What Is An Operating System?
Lots of hardware !!
One or more processors
Main memory
Disks
Printers
Various input/output devices
Managing all these components requires a layer of software – the operating system

4. Where is the software?
Where the operating system fits in.

5. The Operating System as an Extended Machine

6. The Operating System as a Resource Manager
Allow multiple programs to run at the same time
Manage and protect memory, I/O devices, and other resources
Multiplexes (shares) resources in two different ways:
In time
In space

7. Functions of operating system
Process management
Process creation, deletion, suspension and resumption
Process synchronization and inter process communication
Process interactions – deadlock detection, avoidance and correction
Mutitasking
Memory management
Allocate and deallocate memory to process
Manage multiple processes within the memory
Manage the sharing of memory between processes
Determine which processed to load when memory is available

8. Functions of operating system
Storage Management
Directory / File creation and deletion
File system management
File/directory manipulation
Backup and achieve
Free-space management
Disk scheduling
I/O management
Device driver installation
Device interface and management

9. Functions of operating system
Protection and security
File attribute for accidental modification
Provides policy for user
Authentication
Data encryption
Firewall
Networking
Provides different sets of protocols that are used for secure networking
TCP/IP, FTP, POP, SMTP
Interface
CUI
GUI
Interactive

10. History of Operating Systems
Generations:
(1945–55) Vacuum Tubes
(1955–65) Transistors and Batch Systems
(1965–1980) ICs and Multiprogramming
(1980–Present) Personal Computers, Tablets, Phones

11. Transistors and Batch Systems (1)
Figure 1-3. An early batch system. (a) Programmers bring cards to (b)1401 reads batch of jobs onto tape.

12. Transistors and Batch Systems (2)
Figure 1-3. (c) Operator carries input tape to (d) 7094 does computing. (e) Operator carries output tape to (f) 1401 prints output.

13. ICs and Multiprogramming
MULTICS
Timesharing CTSS (MIT)
Multics
UNix
Figure 1-5. A multiprogramming system with three jobs in memory.

14. More third generation . Time Sharing (CTSS) Multics Unix Linux MULTICS
Timesharing CTSS (MIT)
Multics
UNix .

15. Fourth generation . PCs Network Operating Systems
Distributed Operating Systems
MULTICS
Timesharing CTSS (MIT)
Multics
UNix .

16. Multithreaded and Multicore Chips
(a) A quad-core chip with a shared L2 cache. (b) A quad-core chip with separate L2 caches.

17. The Operating System Types
Mainframe operating systems
Big-thousands of disks….
Lots of jobs with lots of I/O
Services-batch (payroll) transactions (airline reservations, timesharing (query database)
Elderly-Unix, Linux replacing them

18. The Operating System Types:

19. The Operating System Types:
Batch operating systems
The users of a batch operating system do not interact with the computer directly.
Each user prepares his job on an off-line device like punch cards and submits it to the computer operator.
To speed up processing, jobs with similar needs are batched together and run as a group.
Disadvantage:
Lack of interaction between the user and the job.
CPU is often idle, because the speed of the mechanical I/O devices is slower than the CPU.
Difficult to provide the desired priority.

20. The Operating System Types:
Server operating systems
Workstations
File, print, web servers
BSD, Linux, Windows
Multiprocessor operating systems
Use multiple cores

21. The Operating System Types:
PC operating systems-Linux, Mac, Windows
Smart phone operating systems- Android, iPhone, Blackberry
No hard disk
Palm, Symbian popular OS’s
Multiprogramming OS
Run multiple program on single core
Advantage: Reduce CPU idle time and utilize it
Disadvantage: Question of security and integrity of user programs and data.

22. The Operating System Types:
Real-Time OS-
Data processing system in which the time interval required to process and respond to inputs is so small that it controls the environment.
The time taken by the system to respond to an input and display of required updated information is termed as response time.
Types:
Hard real-time:
Guarantee that critical tasks complete on time.
Secondary storage is limited or missing with data stored in ROM.
Virtual memory is almost never found.

23. The Operating System Types:
Soft real-time:
Soft real time systems are less restrictive.
Have limited utility than hard real-time systems.
Example: Multimedia, virtual reality, Advanced Scientific Projects like undersea exploration and planetary rovers etc.

24. Operating Systems Structure
Monolithic systems
A main program that invokes the requested service procedure.
A set of service procedures that carry out the system calls.
A set of utility procedures that help the service procedures.

25. Monolithic Systems

26. Easy for error detection
Layered Systems-THE operating system
Components are organized and module are layered them from one top to next
Module are not free to communicate directly without maintaining hierarchy
Easy for error detection

27. Layered Systems-THE operating system
Dijkstra’s the author

28. Layered Systems

29. Microkernels

30. Microkernels Small number of processes are allowed in the kernel
Minimizes effects of bugs
Don’t want bug in driver to crash system
Put mechanism in kernel and policy outside the kernel
Mechanism- schedule processes by priority scheduling algorithm
Policy-assign process priorities in user space

31. Microkernels
Structure of the MINIX 3 system.

32. Microkernels

33. Client-Server Model
Divide operating kernel into several process
I/O server, memory server, thread interface server, print server etc
Servers run in user mode provide service when client demands

34. Client-Server Model
The client-server model over a network.

35. Virtual Machines (1)
The structure of VM/370 with CMS.

36. Virtual Machines (2)
(a) A type 1 hypervisor. (b) A type 2 hypervisor.