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Chapter 3 Operating Systems Introduction to CS 1st Semester, 2016 Sanghyun Park Outline History of Operating Systems Operating System Architecture Coordinating the Machine’s Activities Handling Competition Among Processes Security (skipped) (skipped) History of Operating Systems An Operating System (OS) controls and coordinates usage of a machine’s __________ (CPU, memory, disks, …) Single-processor machines in 1940s and 1950s Significant preparation of mechanical equipment to run a program Execution of a program → ____ Separation of users and equipments (introduction of computer operator concept) Submit program to operator to run, along with any required ____ and special _________ Operator _____ program materials into machine’s mass storage Batch processing – the execution of jobs by collecting them in a single _____, then executing them _______ further _________ with the user Batch Processing ___ interaction with the program once submitted Interactive Processing What happens when we have multiple users? Time-_______ solution (time slices) In single-user systems usually called ___________ Software Classification Application: spreadsheets, games, program development software Utility: utility to format a disk, copy a file, utility to handle network communication Operating system Operating System Components Shell: ________ between users and operating systems Modern computers have a _____ shell Window manager: component within the GUI shell Kernel: ______ part of an OS OS Kernel Software Components File manager Device drivers Coordinates machine’s use of main ________ Scheduler Controls operation of machine’s ________ devices (printer, monitor, …) Memory manager Coordinates use of machine’s mass _______ Determines which ________ is executed ______ Dispatcher Controls allocation of _____ slices to activities Boot Strapping in OS File Manager Keep ________ of files stored in secondary storage _________ of each file Which users are allowed to access which files _________ space in secondary storage Group files into a bundle called a __________ or folder A directory may contain other directories called ____________ A chain of directories within directories is called a directory _____ Provide means to access files (open and manipulate files) Memory Manager Charged with the task of coordinating the machine’s use of main memory Such duties are minimal in ‘one task at a ____’ environment The program for the current task is placed in main memory, executed, and then replaced by the program for the next task The duties are extensive in _________ or multitasking environment Many programs and blocks of data reside in main memory concurrently Allocate areas of memory for each program Fulfill memory requirements for programs Keep track of memory areas no longer occupied Virtual Memory When total main memory required _______ actually available? Memory manager creates _______ of additional memory space by ________ programs and data back and forth between main memory and secondary storage Illusionary memory space is called _______ memory Memory requirements are allocated in units called ______ (page size < 4KB) When a main memory of 256MB is required, but only 128MB is actually available? Memory manager _______ contents of pages in secondary storage When a page in secondary storage is needed for access, _____ it in main memory If no space in main memory, _____ some other page no longer required to secondary storage Concept of a Process Distinction between a program and the activity of executing a program Program static set of directions Activity of executing a program dynamic activity known as a ________ Process state Current ________ in the program being executed (value of PC) _______ in other registers and associated memory cells A single program can be associated with ___________ one process In a time-sharing computer, processes _________ for time slices It is the task of operating system to coordinate these processes Process Administration (1/2) The tasks associated with process coordination are handled by the _________ and _________ within OS kernel Scheduler Maintains a block of information in main memory called _____________ When a new task is assigned to machine, creates a process for that task by placing a new _____ in the process table Memory area assigned to process (from memory manager) Process priority Process status (ready, waiting for some event (I/O for example)) Determines which activity is executed first Dispatcher Ensures that the scheduled processes are actually executed Divides time into time slices (quantum) Process __________ Process Administration (2/2) At interrupt CPU completes current machine _____, _______ current process state, and transfers control to an _________ handler Interrupt handler is part of dispatcher Dispatcher Sometimes, the process time slice is terminated ______ the timer expires (for example when executing I/O) Selects a _____ process from the process table (highest priority) _______ time circuit for the next interrupt Allow selected process to ______ execution
