Introduction to Operating Systems

1. What is an Operating System

  • A program that acts as an intermediary between the user of a computer and the computer hardware
  • Operating system goals
    • Convenience: make the computer system convenient to use
    • Efficiency: Manage the computer system resources in an efficient manner
  • “The one program running at all times on the computer” is the kernel. Everything else is either a system program or an application program.
2. OS Features needed for multiprogramming
  • Job Scheduling: must choose the processes that will be brought to memory
  • Memory Management: must allocate the memory to several jobs
  • CPU Scheduling: must choose among several jobs ready to run
3. Parallel System
  • Multiprocessor systems with more than one CPU in close communication
  • Tightly coupled system
    • processors share memory and a clock;
    • communication usually takes place through the shared memory
  • Advantage of parallel system
    • increased throughput
    • economy of scale
    • increased reliability
4. Distributed Systems
  • Distributed the computation among several physical processors
  • Loosely coupled system
    • each processor has its own local memory
    • processors communicate with one another through various communication lines
  • Advantage of distributed systems
    • resource and load sharing
    • reliability
    • communications

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