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Week 4

Week 4. Operating Systems. Review. Program set of instructions Process / task program in execution Each process has it’s own address space Consisting of instruction region Data region Stack region Process run for an interval or quantum of time. Single-user, dedicated machine.

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Week 4

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  1. Week 4 Operating Systems

  2. Review • Program set of instructions • Process / task program in execution • Each process has it’s own address space • Consisting of instruction region • Data region • Stack region • Process run for an interval or quantum of time

  3. Single-user, dedicated machine Memory OS User program Unused

  4. Uni-programming • Difficult application development • Assembler or machine language • No error recovery • Job scheduling (batch processing) • Processor had to do all operations • Inefficient use of resources • Non real-time

  5. Operating System • Definition “software that controls hardware” • Resource manager - Gatekeeper • Interface between user and hardware • Separates application from hardware • File manager • Kernel is the core component of the OS

  6. OS Objectives and Functions • Convenience • Making the computer easier to use • Efficiency • Allowing better use of computer resources • Simplicity • Application developers can use system procedures to reduce code

  7. Multiprogramming • Carve memory into partitions • Unique app’s loaded into each partition • Operating system switches HW resources between partitions for a quantum of time • Appears to run simultaneously • Efficient use of processor resources • Real-time data • Con = overhead, complex

  8. Hardware M E M O R Y Operating System M E M O R Y Time a Time b Time c Partition 1 Partition 2 Partition 3 Application a Application b Application c

  9. Process states • Running • Ready • Blocked • Wait • Suspended

  10. Scheduling Algorithms • First-In-First-Out FIFO • Round-Robin RR • Shortest-Process-First SPF • Shortest-Remaining-Time SRT • Multilevel Feedback Queue • Fair Share Scheduling

  11. FIFO

  12. RR Job Queue Completion CPU A C B A Preemption

  13. Process control block • PID- Process identification number • PC- Program counter • Registers • State • Priority • Address space • Flags / etc

  14. Layers and Views of a Computer System

  15. Operating System Services • Program creation • Program execution • Access to I/O devices • Controlled access to files • System access • Error detection and response • Accounting

  16. O/S as a Resource Manager

  17. Memory management • Fixed size partitioning • Variable-size partitioning • Fragmentation • Memory leak

  18. Virtual memory Disk Memory 4K Page Segment 4K Page Segment 4K Page Segment 4K Page Segment Free

  19. LPAR

  20. $64 Million Question $$$$$$$$$$$$$$$$$$$$$$$ What does this have to do with security? $$$$$$$$$$$$$$$$$$$$$$$

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