Operating System Concepts: An Introduction to OS Components, Functions, and Management, Study notes of Computer Science

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Operating System Concepts – 8th^ Edition Silberschatz, Galvin and Gagne ©

Chapter 1: Introduction

Chapter 1: Introduction

 (^) What Operating Systems Do  (^) Computer-System Organization  (^) Computer-System Architecture  (^) Operating-System Structure  (^) Operating-System Operations  (^) Process Management  (^) Memory Management  (^) Storage Management  (^) Protection and Security  (^) Distributed Systems  (^) Special-Purpose Systems  (^) Computing Environments  (^) Open-Source Operating Systems

What is an Operating System?

 (^) A program that acts as an intermediary between a user of a computer and the computer hardware.  (^) Operating system goals:  (^) Execute user programs and make solving user problems easier  (^) Make the computer system convenient to use  (^) Use the computer hardware in an efficient manner

Computer System Structure

 (^) Computer system can be divided into four components:  (^) Hardware – provides basic computing resources  (^) CPU, memory, I/O devices  (^) Operating system  (^) Controls and coordinates use of hardware among various applications and users  (^) Application programs – define the ways in which the system resources are used to solve the computing problems of the users  (^) Word processors, compilers, web browsers, database systems, video games  (^) Users  (^) People, machines, other computers

Operating System Definition

 (^) OS is a resource allocator  (^) Manages all resources  (^) Decides between conflicting requests for efficient and fair resource use  (^) OS is a control program  (^) Controls execution of programs to prevent errors and improper use of the computer

Operating System Definition (Cont.)

 (^) No universally accepted definition  (^) “Everything a vendor ships when you order an operating system” is good approximation  (^) But varies wildly  (^) “The one program running at all times on the computer” is the kernel. Everything else is either a system program (ships with the operating system) or an application program.

Computer System Organization

 (^) Computer-system operation  (^) One or more CPUs, device controllers connect through common bus providing access to shared memory  (^) Concurrent execution of CPUs and devices competing for memory cycles

Computer-System Operation

 (^) I/O devices and the CPU can execute concurrently  (^) Each device controller is in charge of a particular device type  (^) Each device controller has a local buffer  (^) CPU moves data from/to main memory to/from local buffers  (^) I/O is from the device to local buffer of controller  (^) Device controller informs CPU that it has finished its operation by causing an interrupt

Interrupt Handling

 (^) The operating system preserves the state of the CPU by storing registers and the program counter  (^) Determines which type of interrupt has occurred:  (^) polling  (^) vectored interrupt system  (^) Separate segments of code determine what action should be taken for each type of interrupt

Interrupt Timeline

Direct Memory Access Structure

 (^) Used for high-speed I/O devices able to transmit information at close to memory speeds  (^) Device controller transfers blocks of data from buffer storage directly to main memory without CPU intervention  (^) Only one interrupt is generated per block, rather than the one interrupt per byte

Storage Structure

 (^) Main memory – only large storage media that the CPU can access directly  (^) Secondary storage – extension of main memory that provides large nonvolatile storage capacity  (^) Magnetic disks – rigid metal or glass platters covered with magnetic recording material  (^) Disk surface is logically divided into tracks , which are subdivided into sectors  (^) The disk controller determines the logical interaction between the device and the computer

Storage-Device Hierarchy

Caching

 (^) Important principle, performed at many levels in a computer (in hardware, operating system, software).  (^) Information in use copied from slower to faster storage temporarily  (^) Faster storage (cache) checked first to determine if information is there.  (^) If it is, information used directly from the cache (fast)  (^) If not, data copied to cache and used there  (^) Cache smaller than storage being cached  (^) Cache management important design problem  (^) Cache size and replacement policy