Lecture 5 Operating Systems

1. Lecture5 Operating Systems Mohammed Arif Mazumder Senior Lecturer, CSE Daffodil International University

2. Today’s lecture • Lecture Outline • Functionality of Operating System (OS) • Survey of Common Operating Systems • Lecture References

3. The Role of An OS • User/ programmer convenience: simple, consistent way for applications to interact with the hardware. • Greater resource utilization: manages the hardware and software resources of the computer system, often invisibly.

4. Benefit for application developers • Don’t have to manage hardware complexity: Application developers can design software for an OS and it will run on all machines that support that OS. The OS hides and manages the hardware complexity and provide an Application Programmer Interface (API).

5. OS Components Device Manager File Manager Kernel Loader Command Interpreter (Shell) GUI

6. Kernel • The heart of the OS • Responsible for all the essential operations like managing resources, task scheduling, etc. • Also contains low-level HW interfaces. • Size important, as it is memory-resident

7. Core Tasks of an OS • Processor management • Memory management • Device management • Storage management • Application Interface • User Interface

8. Processor Management • Various programs compete for the attention of the microprocessor. • The OS plays the role of the honest referee, making sure that each application gets the necessary attention required for its proper execution. • It tries to optimally manages the limited processing capacity of the microprocessor to the greatest good of all the users & apps

9. Memory Management • Straight forward for a single-user, single tasking • The OS ensures that: • each application has enough private memory • applications do not run into other application’s private memory. • The OS is responsible for efficient utilization of hierarchical system memory (e.g. RAM, cache, etc.).

10. Storage Management • A file system is a collection of directories, subdirectories, and files organized in a logical order • The OS is responsible for maintaining the file system through indexing of filenames and their disk location. • The OS can find any file in a logical and timely fashion

11. Device Management • Applications talk to devices through the OS and OS talks to and manages devices through device drivers Example: When we print to a laser printer, we do not need to know its details. All we do is to tell the printer device driver about what needs to be printed and it takes care of the details

12. Application Interface • Application developers do not need to know much about the hardware • The OS provides all applications with a straight-forward and consistent interface to hardware Example: An application uses the OS to store data on the disk drive without knowing exact physical characteristics of the disk.

13. User Interface • Users communicate with the computer using a consistent user interface provided by the OS • This UI can be a command-line interface in which a user types in the commands. Example: copy a:/file1.html c:/file1.html • Or, it can be a graphical UI, where Windows, Icons, Menus, and a Pointing device (such as a mouse) is used to receive and display information. Example: With the help of the mouse, drag file1.html from drive a to drive c

14. Types of Operating Systems Classification according to type of computers and applications they support • Real-Time Operating System (RTOS) • Single-User, Single Task • Single-User, Multi-Tasking • Multi-User

15. RTOS • Used to run computers embedded in machinery, robots, scientific instruments and industrial systems • An important part of an RTOS is managing the resources of the computer so that a particular operation executes in precisely the same amount of time every time it occurs • Examples: QNX, Real-time Linux

16. Single-User, Single Task • OS designed to manage the computer so that one user can effectively do one thing at a time Example: MS-DOS is an example single-tasking single-user OS with a command line interface.

17. Single-User, Multi-Tasking • Most popular OS • Used by most of PCsand Laptops • Lets a single user interact with several programs, simultaneously Examples: Windows, Mac OS, Linux

18. Multi-User • A multi-user OS allows many users to take advantage of the computer's resources, simultaneously Examples: Linux, Unix, Windows Terminal Server

19. Survey of common Operating Systems PCs Embedded Systems for

20. Personal Computer (PC)Operating Systems Microsoft OS Unix or Unix-like OS Other OS

21. 1 Microsoft Operating Systems

22. Disk Operating System (DOS)

29. 2 UNIX or UNIX-like Operating Systems

32. Linux

34. 3 OtherOperating Systems

38. EmbeddedOperating Systems • Microsoft CE • Android • Other Embedded OS

41. Pocket PC OS Palm OS Symbian OS

42. OS Survey Summary

43. Lecture’s Summary • The primary role of OS: 1) simple, consistent way for applications to interact with the hardware &2)to efficiently utilize HW/ SW resources. • Main OS tasks: manages 1)processor, 2)memory, 3) HW devices, 4) storage of computer systems; 5) provides the application and the user interface.