Operating Systems

1. Operating Systems

2. What is an Operating System? • Computer requires two types of software: • Application software • Operating systems software • Used to control and monitor the running of application programs • Allow the users to interact with the computer’s hardware & software

3. Operating System • Typically consists of a number of programs (System Software) • Usually bundled with the hardware

4. How it works? • Each time you switch on your PC, the operating systems kernel (the part you need in memory at all times) is copied from your hard disk into memory.

5. What is the Kernel? www.wikipedia.org • Central component of an operating system • Responsible for servicing resource requests between applications and hardware • A kernel has facilities to receive resource requests and grant access to resources such as allocating space for a new file or creating a network connection. • Kernels use a system call interface to handshake with applications

6. What is it responsible for? www.wikipedia.org • Process management • Memory management • Device management • System calls

7. Process management • The kernel dictates which programs run and when they run by creating various processes and threads within those processes. • A process is nothing more than some memory allocated to a running program, and the threads are individual streams of execution within a process. • The kernel orchestrates various processes and their threads so that multiple programs can run simultaneously and transparently on the same machine. http://e-articles.info/e/a/title/What-Is-the-Kernel/

8. Memory Management • The kernel allocates memory to running programs, and frees that memory when it is no longer required. • This memory control is implemented in the kernel's virtual memory management function, which utilises physical RAM and hard drive space to store information for running processes http://e-articles.info/e/a/title/What-Is-theKernel/

9. Device management • When various hardware components of the machine need attention (e.g., a packet arriving on the network interface) or a program encounters an usual event (e.g., division by zero), the kernel is responsible for determining how to handle the resulting interrupts. • By taking care of the interrupt itself using kernel code or sending information to a particular process to deal with it, the kernel keeps the system operating smoothly. • Manages Plug and Play in Windows http://e-articles.info/e/a/title/What-Is-theKernel/

10. System calls • A system call is how a program requests a service from an operating system's kernel that it does not normally have permission to run. System calls provide the interface between a process and the operating system. www.wikipedia.org

11. Some of the functions of an Operating System • Interface (File Management) • File System • Task Management • Machine and peripheral management • Device Drivers

12. Interface A user interface is the system by which people (users) interact with a machine. The user interface includes hardware (physical) and software (logical) components. User interfaces exist for various systems, and provide a means of input and output.

13. Types of Interface Command Driven Interface Graphical User Interface - GUI

14. File System A file system (often also written as filesystem) is a method of storing and organising computer files and the data they contain to make it easy to find and access them. en.wikipedia.org/wiki/File_system

15. FAT – File Allocation Table • A table that the operating system uses to locate files on a disk. Due to fragmentation, a file may be divided into many sections that are scattered around the disk. The FAT keeps track of all these pieces. • FAT file systems are commonly found on floppy disks, flash memory cards, digital cameras, and many other portable devices because of their relative simplicity. en.wikipedia.org/wiki/File_system

16. FAT http://www.pcguide.com/ref/hdd/file/partSizes-c.html Worth a visit

17. MS DOS • FAT12 • FAT16 • Newer versions of DOS can support FAT32 however legacy DOS can not.

18. NTFS • NTFS (New Technology File System) is the standard file system of Windows NT, including its later versions Windows 2000, Windows XP, Windows Server 2003, Windows Server 2008, Windows Vista, and Windows 7. • NTFS supersedes the FAT file system as the preferred file system for Microsoft’s Windows operating systems. • en.wikipedia.org/wiki/File_system

19. NTFS • When a file is created using NTFS, a record about the file is created in a special file, the Master File Table (MFT). • The record is used to locate a file's possibly scattered clusters. NTFS tries to find contiguous storage space that will hold the entire file (all of its clusters). • Each file contains, along with its data content, a description of its attributes (its metadata).

20. NTFS • It provides security by supporting access control and ownership privileges, meaning you can set permission for groups or individual users to access certain files. • NTFS supports compression of individual files and folders which can be read and written to while they are compressed. • NTFS is a recoverable file system, meaning it has the ability to undo or redo operations that failed due to such problems as system failure or power loss • Encryption - The NTFS file system can automatically encrypt and decrypt file data as it is read and written to the disk.

21. Windows • Windows XP Professional supports the FAT16, FAT32, and NTFS file systems.

22. Task Management • A multitasking operating system is any type of system that is capable of running more than one program at a time. • Most modern operating systems are configured to handle multiple programs simultaneously.

23. Task Management • With older examples of the multitasking operating system, managing two or more tasks normally involved switching system resources back and forth between the two running processes. • The system would execute tasks for one, freeze that program for a few seconds, and then execute tasks for the other program. While this approach did create a short time lag for the operator, this lag was usually no more than a few seconds, and still offered considerable more efficiency than the older single-task operating system.

24. Task Management • Single tasking As the name implies, this operating system is designed to manage the computer so that one user can effectively do one thing at a time.

25. Machine & Peripheral Management • The Operating System talks to the devices in a computer system using device drivers that are special programs designed to interact with the physical devices of the system. • The device manager isolates the device drivers from the Kernel of the OS and the user applications from the system’s hardware.  It acts as an interface between the device drivers and both the kernel and user applications. Interrupt • An interrupt is a signal that informs the processor that a particular device wants its attention.  The processor responds to the request, saves the status of the current activity, executes the requested activity and on completion, retrieves the saved activity and resumes the same.  Interrupts are of two types, Hardware Interrupts and Software Interrupts. How does Windows manage it peripherals?

26. Drivers • Device drivers are small files that act like an interface between hardware in a computer system and the operating system (OS). • Hardware requires device drivers so that the OS can “see” the devices and handle them effectively and efficiently. • Common components that require drivers include keyboards, mice, controllers, graphics cards and audio hardware. Do some operating systems come with pre-installed drivers (OEM)?

27. Task • Use DOS, try out some of the commands. • Do the same activities within Windows. • What was the difference? • Research and document the functions and features of both operating systems.