EC503 - OPERATING SYSTEMS

1. EC503 - OPERATING SYSTEMS TOPIC 2 - BASIC OPERATING SYSTEM CONCEPT MANAGEMENT

2. SUB-TOPICS

3. USER INTERFACES

4. What is a User Interface (UI)?

5. What is a User Interface (UI)?

6. Types of UI

7. Command Driven UI • The Command Driven Interface is text-based interface, where the user types in commands via the keyboard. • Commands usually are typed one line at a time. • Examples of command-driven interface are MS-DOS, Linux and Unix.

8. Command Driven UI

9. Menu-Based UI • Menu is a list of options which the user may select an operation to be preformed. • There are two main types of menu: • Pull-Down. • Pop-Up. • Restricted number of choices offered to the user which may lead to further sub-menus. • Typically with touch screen e.g. information bureaus.

10. Menu-Based UI

11. Graphical UI • Graphical User interface (GUI) is a type of interface that allows the user to control a computer’s input, storage and output through graphical elements. • Most popular today is WIMP (windows, icons, menus, pointer). • View different applications or files in windows. • Use some sort of pointing device to select options in menus and small pictures (icons).

12. Graphical UI

13. Graphical UI

14. Form-Based UI • Replicates a hard copy paper form. • Specified areas for the data which may have helpful instructions (usually by clicking a ? mark by the text box). • E.g. boxes for input of coded material like the date or the sex of the customer, and areas to be filled in with textual information. • Can contain radio buttons and/or drop down lists. • A cursor moves to the next box to be filled in. • Highlighted boxes make it clear where the data is to be inserted • User can be forced to enter data before being allowed to continue. • Checks can be made to make sure input is sensible for that box before moving on to the next. • Uses: Telephone sales, order forms.

15. Form-Based UI

16. Voice-Actuated UI • Speech-driven interfaces • Familiar to user • Speech recognition or typed natural language • Problems: • Vague. • Ambiguous. • Hard to do well! • Solutions: • Try to understand a subset. • Pick on key words.

17. FILE SYSTEM

18. What is a File?

19. Types of Files • Data: • Numeric, Character, Binary. • Program: • Source, Object (Load Image). • Documents.

20. What is a File System?

21. Functions of a File System • Act as one of the component of file management services provided by the OS. • Manages: • Directory structures for convenient grouping of files. • Protection of files against illegal accesses. • File sharing semantics for concurrent accesses to a file. • Reliable storage of files.

22. INPUT / OUTPUT CONTROL SYSTEM (IOCS)

23. IOCS?

24. IOCS? • Act as the other component of file management services provided by the OS. • Manages: • Efficiency of I/O devices operation. • Efficient access to data in a file.

25. Physical & Logical I/O • I/O processes that happened in a computer can be divided into two: • Physical I/O (PIO). • Logical I/O (LIO). • PIO is the read/write process to the physical disk available on the system. • LIO is the read/write process of buffer cache. • Cache is the data that was taken from physical disk and put into memory for faster and more efficient access.

26. Directory Management

27. Directory Management • A directory contains information about a group of files. • Each entry in a directory contains the attributes of one files, such as its type, organization, size, location and the manner in which it may be accessed by various users in the system. • Directories can be classified into: • Single-Level Directory. • Two-Level Directory. • Hierarchical Directory.

28. Single-Level Directory Systems • A single level directory system: • Contains 4 files. • Owned by 3 different people, A, B, and C.

29. Two-Level Directory Systems • Letters indicate owners of the directories and files.

30. Hierarchical Directory Systems • A hierarchical directory system.

31. Disk Space Management • Low-level formatting, or physical formatting - dividing a disk into sectors that the disk controller can read and write. • To use a disk to hold files, the operating system still needs to record its own data structures on the disk. • Partition the disk into one or more groups of cylinders. • Logical formatting or “making a file system”. • Boot block initializes system. • The bootstrap is stored in ROM. • Bootstrap loader program.

32. Disk Space Management Contiguous allocation of disk space for 7 files. State of the disk after files D and E have been removed.

33. BOOT PROCESS

34. Boot or Boots? Boot is actually a shorter word for bootstrap.

35. Why Boot? • Hardware doesn’t know where the operating system resides and how to load it. • Need a special program to do this job - Bootstrap loader(e.g. BIOS - Basic Input Output System). • Bootstrap loader locates the kernel, loads it into main memory and starts its execution. • In some systems, a simple bootstrap loader fetches a more complex boot program from disk, which in turn loads the kernel.

36. Boot Up Tasks • Run diagnostics to determine the state of machine. • If diagnostics pass, booting continues. • Runs a Power-On Self Test (POST) to check the devices that the computer will rely on, are functioning. • BIOS goes through a preconfigured list of devices until it finds one that is bootable. • If it finds no such device, an error is given and the boot process stops. • Initializes CPU registers, device controllers and contents of the main memory. • After this, it loads the OS.

37. Boot Up Tasks • On finding a bootable device, the BIOS loads and executes its boot sector. • In the case of a hard drive, this is referred to as the master boot record (MBR) and is often not OS specific. • The MBR code checks the partition table for an active partition. • If one is found, the MBR code loads that partition's boot sector and executes it. • The boot sector is often operating system specific, however in most operating systems its main function is to load and execute a kernel, which continues start-up.