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Chapter 3: Operating Systems

Chapter 3: Operating Systems. Computer Science: An Overview Tenth Edition by J. Glenn Brookshear. Functions of Operating Systems. Oversee operation of computer Store and retrieve files Schedule programs for execution Coordinate the execution of programs The best known examples: Windows

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Chapter 3: Operating Systems

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  1. Chapter 3: Operating Systems Computer Science: An OverviewTenth Edition by J. Glenn Brookshear

  2. Functions of Operating Systems • Oversee operation of computer • Store and retrieve files • Schedule programs for execution • Coordinate the execution of programs • The best known examples: • Windows • Unix • Linux

  3. Evolution of Shared Computing • The execution of each program is called job. • Batch processing • Execution of jobs in a single batch, no interaction with user • Interactive processing • Requires real-time processing • Execution of jobs through dialogue with user via remote terminals • Time-sharing/Multitasking • Rotate jobs • Implemented by Multiprogramming • Multiprocessor machines

  4. Figure 3.1 Batch processing

  5. Figure 3.2 Interactive processing

  6. Types of Software • Application software • Performs specific tasks for users • System software • Provides infrastructure for application software • Consists of operating system and utility software • Utility Software • Programs for performing activitis that are fundamental to computer installation but not included in OS. • Ex: sw to format a disk

  7. Operating System Components • Shell: Communicates with users • Text based • Graphical user interface (GUI) • Kernel:internal part of OS. • File manager: coordinate the machine’s mass storage facilities • Device drivers: communicate with controllers • Memory manager: coordinate machine use of memory • Scheduler / dispatcher: determines which activities are to be considered for execution / controls the allocation of time to these activities

  8. Figure 3.4 The shell as an interface between users and the operating system

  9. File Manager • Directory (or Folder): A user-created bundle of files and other directories (subdirectories) • Directory Path: A sequence of directories within directories

  10. Memory Manager • Allocates space in main memory • May create the illusion that the machine has more memory than it actually does (virtual memory) by playing a “shell game” in which blocks of data (pages) are shifted back and forth between main memory and mass storage • Ex:

  11. Getting it Started (Bootstrapping) • Bootstrap: Program in ROM (example of firmware) • Run by the CPU when power is turned on • Transfers operating system from mass storage to main memory • Executes jump to operating system

  12. Figure 3.5 The booting process

  13. Processes • Process: The activity of executing a program • Process State: Current status of the activity • Program counter • General purpose registers • Related portion of main memory

  14. Process Administration • Scheduler: Adds new processes to the process table and removes completed processes from the process table • Dispatcher: Controls the allocation of time slices to the processes in the process table • The end of a time slice is signaled by an interrupt.

  15. Figure 3.6 Time-sharing between process A and process B

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