1. File System Organisation and Implementation

1. Real Time Operating Systems: Lesson-2: OS File System, IO- Subsystems, Security, NOS and Mobile OS

2. 1. File System Organisation and Implementation

3. File - a named entity - on a magnetic disc, optical disc, or system memory. - a structured data, characters and - Each OS may have differing abstractions for a file - A file may be a structured record on a texts. RAM

4. POSIX standard for file operations - as a byte stream. with the record of bytes NT Functions – createFile, ReadFile WriteFile, SetFilePointer and Window NT file – a named entity closeHandle

5. Set of Commands in the POSIX File-System write ( ) – wiring into the file [Like fwrite in ‘C’ read ( ) – read ( ) – read into the file lseek ( )-Set the pointer at for next RD/WR close ( ) – Closing a file Open ( ) – File creation and activation fcntl ( ) –file control

6. Application Software Application Programming Interface (API) • Block File System - application generates records to be saved into the memory. A file pointer (record) points to a block from the start to the end of the file • Byte Stream File-System: A file pointer (record) points to a block from the start to the end of the file

7. File Descriptor (similar to a TCB)

8. identity • state – closed, archived • locks and protection fields - • file info – present length, when • created, when last modified • creator or owner • sharing permission

9. count – Number of directories • media storage details - • blocks transferable per access referring to it

10. 2. IO Subsystems

11. Application Software Application Programming Interface (API) • IO ports are the subsystems of OS device management systems • I/O system differs in the different OSs • I/O system differs in the different OSs.

12. IO subsystem Hierarchy in a typical OS IO system

13. Layer 1: Application • Layer 3- O Device Driver Functions Layer 4 – Device Hardware/ Port/ • Interface Card Layer 2: IO Basic Functions

14. Set of Commands for synchronous and asynchronous IOs aio_write( ) – asynchronous IO read aio_list( ) – list asynchronous IO requests aio_error ( ) – retrieve error status aio_read ( ) – asynchronous IO read aio_cancel – suspend operation

15. 3. Network OS (NOS)

16. Network means exchange of data frames in the LANs of packets between different host devices (interfaces). Exchange is either in client-server mode or peer-to-peer mode .

17. Protocols FTP Telnet Communication char device like TCP/IP block device like

18. NOS Definitions • “an operating system that includes special functions for connecting computers and devices into a local area network (LAN).” • “an OS that has functions for protocol-stacks (for example TCP/IP or Ethernet 80.2.3) plus network device drivers”.

19. The basic OS has networking functions built-in but a Network operating system usually has software that enhances the basic OS by adding network operation features.

20. An NOS provides: • remote logins • remote file transfers • interconnections between network devices NOS Kernel handles: • Address Resolution issues

21. packet identification, • dispatch to appropriate device • interconnections between network devices NOS Kernel essential for host systems on the network.

22. Exemplary NOSs

23. Application Software • Application Programming Interface (API) • Arcnet • Banyan Vines • PC-NFS, • Novel Netware,

24. 4. Mobile OSs

25. Mobile OS definition: an OS for mobile systems, handheld devices, PDA, telephone, palm computers and pocket computers.

26. Mobile OSs support the protocols IrDA (Infrared Data Association), Bluetooth and Zigbee so that it connect by infrared and wireless to devices and computer at short distances.

27. Mobile OS means: • OS of mobile computing or embedded systems (laptop computers or handheld or wireless devices). Examples of mobile OS- Windows CE, Palm OS, PocketPC and Mac OS X Jaguar [for connecting the VPN (Virtual Private Networks] Window XP, PC OS and Symbian

28. 3. OS Security Issues

29. OS should provide protection mechanisms and implement a system administrator (s) defined security policy. For example, a system administrator can define the use of resources to the registered and authorised users (and hence their processes).

30. Important security Functions Confinement Mechanism Security Policy (Strategy) Authentication Mechanism Authorisation Mechanism Controlled resource sharing Encryption

31. Summary

32. We learnt • File Manager creates, opens, reads, seeks a record, writes, and closes a file. A file has a file descriptorlike a TCB. • I/O subsystems are an important part of OS services. Example: UART access and the parallel port access.

33. We learnt (iii) Network operating system is an OS that includes special functions for connecting computers and devices into a local area network (LAN). It is an OS that has functions for protocol-stacks (for example TCP/IP or Ethernet 802.3) plus network device drivers.

34. We learnt (iv) PocketPC, Windows CE, Palm OS are popular mobile OSs. Embedded systems for mobile systems employ the mobile OSs

35. We learnt (v) The OS security issues are important considerations and (vi) Protection of memory and resources from any unauthorised write into the PCB or resource, or mix up of accesses of one by another, becomes imperative from an OS security and protection mechanism

36. We learnt (vi) PocketPC, Windows CE, Palm OS are popular mobile OSs. Embedded systems for mobile systems employ the mobile OSs

37. End of Lesson 2 Subsystems, Security, NOS and Mobile OS